Abstract:
The Chiral Magnetic Effect (CME) is a macroscopic manifestation of fundamental chiral anomaly in a many-body system of chiral fermions, and emerges as an anomalous transport current in the fluid dynamics framework. Experimental observation of the CME is of great interest and has been reported in Dirac and Weyl semimetals. Significant efforts have also been made to look for the CME in heavy ion collisions. Critically needed for such a search is the theoretical prediction for the CME signal. In this paper we report a first quantitative modeling framework, Anomalous Viscous Fluid Dynamics (AVFD), which computes the evolution of fermion currents on top of realistic bulk evolution in heavy ion collisions and simultaneously accounts for both anomalous and normal viscous transport effects. AVFD allows a quantitative understanding of the generation and evolution of CME-induced charge separation during the hydrodynamic stage, as well as its dependence on theoretical ingredients. With reasonable estimates of key parameters, the AVFD simulations provide the first phenomenologically successful explanation of the measured signal in 200 AGeV AuAu collisions.
Y. Jiang, S. Shi, Y. Yin, J. Liao: Quantifying Chiral Magnetic Effect from Anomalous-Viscous Fluid Dynamics, Chinese Physics C 42 (2018) 011001
https://doi.org/10.1088/1674-1137/42/1/011001
Related to Project A02, B03, C06
Abstract:
The study of the Berezinskii-Kosterlitz-Thouless transition in two-dimensional |φ|4 models can be performed in several representations, and the amplitude-phase (AP) Madelung parametrization is a natural way to study the contribution of density fluctuations to nonuniversal quantities. We introduce a functional renormalization group scheme in AP representation where amplitude fluctuations are integrated first to yield an effective sine-Gordon model with renormalized superfluid stiffness. By a mapping between the lattice XY and continuum |φ|4 models, our method applies to both on equal footing. Our approach correctly reproduces the existence of a line of fixed points and of universal thermodynamics and it allows to estimate universal and nonuniversal quantities of the two models, finding good agreement with available Monte Carlo results. The presented approach is flexible enough to treat parameter ranges of experimental relevance.
N. Defenu, A. Trombettoni, I. Nandori, T. Enss: Nonperturbative renormalization group treatment of amplitude fluctuations for |φ|4 topological phase transitions, Phys. Rev. B 96 (2017) 174505
https://doi.org/10.1103/PhysRevB.96.174505
Related to Project C02, C03
Abstract:
We study the impact of attractive self-interactions on the nonequilibrium dynamics of relativistic quantum fields with large occupancies at low momenta. Our primary focus is on Bose-Einstein condensation and nonthermal fixed points in such systems. For a model system, we consider O(N)-symmetric scalar field theories. We use classical-statistical real-time simulations as well as a systematic 1/N expansion of the quantum (two-particle-irreducible) effective action to next-to-leading order. When the mean self-interactions are repulsive, condensation occurs as a consequence of a universal inverse particle cascade to the zero-momentum mode with self-similar scaling behavior. For attractive mean self-interactions, the inverse cascade is absent, and the particle annihilation rate is enhanced compared to the repulsive case, which counteracts the formation of coherent field configurations. For N≥2, the presence of a nonvanishing conserved charge can suppress number-changing processes and lead to the formation of stable localized charge clumps, i.e., Q balls.
J. Berges, K. Boguslavski, A. Chatrchyan, J. Jäckel: Attractive versus repulsive interactions in the Bose-Einstein condensation dynamics of relativistic field theories, Phys. Rev. D 96 (2017) 076020
https://doi.org/10.1103/PhysRevD.96.076020
Related to Project A03, A04, A05, B03
Abstract:
The realization of the strong coupling regime between a single cavity mode and an electromagnetic resonance is a centrepiece of quantum optics. In this regime, the reversible exchange of a photon between the two components of the system leads to so-called Rabi oscillations. Strong coupling is used in the optical and infrared regimes, for instance, to produce non-classical states of light, enhance optical nonlinearities and control quantum states. Here, we report the first observation of Rabi oscillations of an X-ray photon between two resonant 57Fe layers embedded in two coupled cavities. The system is described by an effective Hamiltonian, in which the two layers couple strongly. We observe sinusoidal beating as the signature of the Rabi oscillations in the system’s temporal evolution, as well as the splitting of nuclear resonances in the reflected light spectrum. Our results significantly advance the development of the new field of X-ray quantum optics.
J. Haber, X. Kong, C.Strohm, S. Willing, J. Gollwitzer, L. Bocklage, R. Rüffer, A. Pálffy, R. Röhlsberger: Rabi oscillations of X-ray radiation between two nuclear ensembles, Nat. Photon. 11 (2017) 720
https://www.nature.com/articles/s41566-017-0013-3
Related to Project B02
Abstract:
We present a systematic calculation of the corrections of the stress-energy tensor and currents of the free boson and Dirac fields up to second order in thermal vorticity, which is relevant for relativistic hydrodynamics. These corrections are non-dissipative because they survive at general thermodynamic equilibrium with non vanishing mean values of the conserved generators of the Lorentz group, i.e. angular momenta and boosts. Their equilibrium nature makes it possible to express the relevant coefficients by means of correlators of the angular-momentum and boost operators with stress-energy tensor and current, thus making simpler to determine their so-called “Kubo formulae”. We show that, at least for free fields, the corrections are of quantum origin and we study several limiting cases and compare our results with previous calculations. We find that the axial current of the free Dirac field receives corrections proportional to the vorticity independently of the anomalous term.
M. Buzzegoli, E. Grossi, F. Becattini: General equilibrium second-order hydrodynamic coefficients for free quantum fields, JHEP 1710 (2017) 091, Erratum: JHEP 1807 (2018) 119
https://doi.org/10.1007/JHEP10(2017)091
Related to Project C06
Abstract:
Numerous few-electron atomic systems are considered which can be used effectively for observing a potential variation of the fine-structure constant α and the electron-proton mass ratio
me/mp. We examine optical magnetic dipole transitions between hyperfine-structure components in heavy highly charged H-like and Li-like ions with observably high sensitivity to a variation of α and me/mp. The experimental spectra of the proposed systems consist of a strong single line, which simplifies significantly the data analysis and shortens the necessary measurement time. Furthermore, we propose systems for an experimental test of the variation of quark masses and discuss the expected level of accuracy in assessing its limitations. Finally, we establish which constraints on the variation of these fundamental constants could be provided by measurements with a hyperfine-structure highly-charged-ion clock and some reference clock, showing that a significant improvement of the current limitations can be reached.
N. S. Oreshkina, S. M. Cavaletto, N. Michel, Z. Harman, C. H. Keitel: Hyperfine splitting in simple ions for the search of the variation of fundamental constants, Phys. Rev. A 96 (2017) 030501(R)
https://doi.org/10.1103/PhysRevA.96.030501
Related to Project B02
Abstract:
We present a parametric estimate of photon production at early times in heavy-ion collisions based on a consistent weak coupling thermalization scenario. We quantify the contribution of the off-equilibrium Glasma phase relative to that of a thermalized Quark-Gluon Plasma. Taking into account the constraints from charged hadron multiplicity data, the Glasma contribution is found to be significant especially for large values of the saturation scale.
J. Berges, K. Reygers, N. Tanji, R. Venugopalan: “How brightly does the Glasma shine? Photon production off-equilibrium”, Nucl.Phys. A 967 (2017) 708
https://doi.org/10.1016/j.nuclphysa.2017.04.034
Related to Project A01, A02, C06
Abstract:
The presence of correlations between particles significantly separated in pseudorapidity in proton-proton and proton-nucleus collisions has raised questions about whether collective effects are observed in small collision systems as well as in heavy-ion collisions. The quantification of these long-range correlations by vn coefficients is of particular interest. A selection of the latest vn measurements is presented, including results from the recent d+Au beam energy scan at RHIC where a significant non-zero v2 is measured down to low center-of-mass energies (√sNN = 39 TeV). Results from a collision system scan – comprising p+Au, d+Au, and 3He+Au collisions – are also shown to address the role of the initial nuclear geometry in the final state anisotropy. Finally, the challenge of measuring multi-particle cumulants, particularly c2{4}, in p+p collisions is discussed, and new methods for reducing the effects of non-flow are shown to produce a more robust measurement of v2{4} in p+p collisions.
A. Ohlson: Collective behavior in small systems, Nucl. Phys. A 967 (2017) 97
https://doi.org/10.1016/j.nuclphysa.2017.06.023
Related to Project A01, A02, A03, A04, C06
Abstract:
Many measurements of quarkonium suppression at the LHC, e.g. the nuclear modification factor RAA J/ψ of , are well described by a multitude of different models. Thus pinpointing the underlying physics aspects is difficult and guidance based on first principles is needed. Here we present the current status of our ongoing high precision study of in-medium spectral properties of both bottomonium and charmonium based on NRQCD on the lattice. This effective field theory allows us to capture the physics of quarkonium without modeling assumptions in a thermal QCD medium. In our study a first principles and realistic description of the QCD medium is provided by state-of-the-art lattices of the HotQCD collaboration at almost physical pion mass. Our updated results corroborate a picture of sequential modification of states with respect to their vacuum binding energy. Using a novel low-gain variant of the Bayesian BR method for reconstructing spectral functions we find that remnant features of the Upsilon may survive up to T ~ 400MeV, while the xb signal disappears around T ~ 270MeV. The cc analysis hints at melting of xc below T ~ 190MeV while some J/ψ remnant feature might survive up to T ~ 245MeV. An improved understanding of the numerical artifacts in the Bayesian approach and the availability of increased statistics have made possible a first quantitative study of the in-medium ground state masses, which tend to lower values as T increases, consistent with lattice potential based studies.
S. Kim, P. Petreczky, A. Rothkopf: High statistics study of in-medium S- and P-wave quarkonium states in lattice Non-relativistic QCD, Nucl. Phys. A 967 (2017) 724
https://doi.org/10.1016/j.nuclphysa.2017.04.010
Related to Project C05
Abstract:
Several recent experiments in atomic, molecular, and optical systems motivated a huge interest in the study of quantum long-range systems. Our goal in this paper is to present a general description of their critical behavior and phases, devising a treatment valid in d dimensions, with an exponent d+σ for the power-law decay of the couplings in the presence of an O(N) symmetry. By introducing a convenient ansatz for the effective action, we determine the phase diagram for the N-component quantum rotor model with long-range interactions, with N=1 corresponding to the Ising model. The phase diagram in the σ−d plane shows a nontrivial dependence on σ. As a consequence of the fact that the model is quantum, the correlation functions are anisotropic in the spatial and time coordinates for σ smaller than a critical value, and in this region the isotropy is not restored even at criticality. Results for the correlation length exponent ν, the dynamical critical exponent z, and a comparison with numerical findings for them are presented.
N. Defenu, A.Trombettoni, S. Ruffo: Criticality and phase diagram of quantum long-range O(N) models, Phys. Rev. B 96 (2017) 104432
https://doi.org/10.1103/PhysRevB.96.104432
Related to Project C02
Abstract:
Universal scaling behavior in the relaxation dynamics of an isolated two-dimensional Bose gas is studied by means of semi-classical stochastic simulations of the Gross–Pitaevskii model. The system is quenched far out of equilibrium by imprinting vortex defects into an otherwise phase-coherent condensate. A strongly anomalous non-thermal fixed point is identified, associated with a slowed decay of the defects in the case that the dissipative coupling to the thermal background noise is suppressed. At this fixed point, a large anomalous exponent η ≃ -3 and, related to this, a large dynamical exponent z ≃ 5 are identified. The corresponding power-law decay isfound to be consistent with three-vortex-collision induced loss. The article discusses these aspects of non-thermal fixed points in the context of phaseordering kinetics and coarsening dynamics, thus relating phenomenological and analytical approaches to classifyingfar-from-equilibrium scaling dynamics with each other. In particular, a close connection between the anomalous scaling exponent η, introduced in a quantum-field theoretic approach, and conservation-law induced scaling in classical phase-ordering kinetics is revealed. Moreover, the relation to superfluid turbulence as well as to driven stationary systems is discussed.
M. Karl, T. Gasenzer: Strongly anomalous non-thermal fixed point in a quenched two-dimensional Bose gas, New. J. Phys. 19 (2017) 093014
https://iopscience.iop.org/article/10.1088/1367-2630/aa7eeb/meta
Related to Project A04, B03
Abstract:
In an ensemble of identical atoms, cooperative effects like sub- and superradiance may alter the decay rates and the energies of specific transitions may be shifted from the single-atom value by the so-called collective Lamb shift. While such effects in ensembles of two-level systems are by now well understood, realistic multilevel systems are more difficult to handle. In this work we show that in a system of atoms under the action of an external magnetic field, the collective contribution to the level shifts can amount to sizable quantitative and qualitative deviations from the single-atom Zeeman splitting picture. We develop a formalism to describe single-photon superradiance in multilevel systems and identify three-parameter regimes, two of which present measurable deviations in the radiation spectrum compared to the case of single-atom magnetic-field-induced splitting.
X. Kong, A. Pálffy: Collective radiation spectrum for ensembles with Zeeman splitting in single-photon superradiance, Phys. Rev. A 96 (2017) 033819
https://doi.org/10.1103/PhysRevA.96.033819
Related to Project B02
Abstract:
The production of the K*(892) strange resonance in Pb+Pb collisions at √sNN = 2.76 TeV LHC energy is analyzed within the integrated hydrokinetic model (iHKM) at different equations of state of superdense matter. The similar analysis is done also for the RHIC top energy √sNN = 200 GeV for comparison purposes. A modification of experimental K*(892)-identification is studied for different centralities in view of possible re-scattering of the decay products at the afterburner stage of the fireball evolution. We see quite intensive rescattering of the decay products as well as recombination processes for K*(892). In addition, the production of the much longer-long-lived φ(1020) resonance with hidden strange quark content is investigated.
B. Braun-Munzinger, V.M. Shapoval, Y.M.S. Sinyukov: K*(892) and φ(1020) production and their decay into the hadronic medium at the Large Hadron Collider, Nucl. Phys. A 968 (2017) 391
https://doi.org/10.1016/j.nuclphysa.2017.09.002
Related to Project C05, C06
Abstract:
We study asymptotic safety of models of the higher derivative quantum gravity with and without matter. The beta functions are derived by utilizing the functional renormalization group, and non-trivial fixed points are found. It turns out that all couplings in gravity sector, namely the cosmological constant, the Newton constant, and the R 2 and R 2μν coupling constants, are relevant in case of higher derivative pure gravity. For the Higgs-Yukawa model non-minimal coupled with higher derivative gravity, we find a stable fixed point at which the scalar-quartic and the Yukawa coupling constants become relevant. The relevant Yukawa coupling is crucial to realize the finite value of the Yukawa coupling constants in the standard model.
Y. Hamada, M. Yamada: Asymptotic safety of higher derivative quantum gravity non-minimally coupled with a matter system, J. High Energ. Phys. (2017) 070
https://doi.org/10.1007/JHEP08(2017)070
Related to Project C01
Abstract:
By analyzing spin-spin correlation functions at relatively short distances, we show that equilibrium near-critical properties can be extracted at short times after quenches into the vicinity of a quantum critical point. The time scales after which equilibrium properties can be extracted are sufficiently short so that the proposed scheme should be viable for quantum simulators of spin models based on ultracold atoms or trapped ions. Our results, analytic as well as numeric, are for one-dimensional spin models, either integrable or nonintegrable, but we expect our conclusions to be valid in higher dimensions as well.
M. Karl, H. Cakir, J. C. Halimeh, M. K. Oberthaler, M. Kastner, T. Gasenzer: Universal equilibrium scaling functions at short times after a quench, Phys. Rev. E 96 (2017) 022110
https://doi.org/10.1103/PhysRevE.96.022110
Related to Project A04
Abstract:
Spectroscopy of nuclear resonances offers a wide range of applications due to the remarkable energy resolution afforded by their narrow linewidths. However, progress toward higher resolution is inhibited at modern x-ray sources because they deliver only a tiny fraction of the photons on resonance, with the remainder contributing to an off-resonant background. We devised an experimental setup that uses the fast mechanical motion of a resonant target to manipulate the spectrum of a given x-ray pulse and to redistribute off-resonant spectral intensity onto the resonance. As a consequence, the resonant pulse brilliance is increased while the off-resonant background is reduced. Because our method is compatible with existing and upcoming pulsed x-ray sources, we anticipate that this approach will find applications that require ultranarrow x-ray resonances.
K. P. Heeg, A. Kaldun, C. Strohm, P. Reiser, C. Ott, R. Subramanian, D. Lentrodt, J. Haber, H. C. Wille, S. Görttler, R. Ruffer, C. H. Keitel, R. Rohlsberger, T. Pfeifer, J. Evers: Spectral narrowing of x-ray pulses for precision spectroscopy with nuclear resonances, Science 357 (2017) 375
https://doi.org/10.1126/science.aan3512
Related to Project B02
Abstract:
We discuss a novel worldline framework for computations of the chiral magnetic effect (CME) in ultrarelativistic heavy-ion collisions. Starting from the fermion determinant in the QCD effective action, we show explicitly how its real part can be expressed as a supersymmetric worldline action of spinning, colored, Grassmannian particles in background fields. Restricting ourselves for simplicity to spinning particles, we demonstrate how their constrained Hamiltonian dynamics arises for both massless and massive particles. In a semiclassical limit, this gives rise to the covariant generalization of the Bargmann-Michel-Telegdi equation; the derivation of the corresponding Wong equations for colored particles is straightforward. In a previous paper [N. Mueller and R. Venugopalan, arXiv:1701.03331.], we outlined how Berry’s phase arises in a nonrelativistic adiabatic limit for massive particles. We extend the discussion here to systems with a finite chemical potential. We discuss a path integral formulation of the relative phase in the fermion determinant that places it on the same footing as the real part. We construct the corresponding anomalous worldline axial-vector current and show in detail how the chiral anomaly appears. Our work provides a systematic framework for a relativistic kinetic theory of chiral fermions in the fluctuating topological backgrounds that generate the CME in a deconfined quark-gluon plasma. We outline some further applications of this framework in many-body systems.
N. Müller, R. Venugopalan: World-line construction of a covariant chiral kinetic theory, Phys.Rev. D 96 (2017) 016023
https://doi.org/10.1103/PhysRevD.96.016023
Related to Project A01
Abstract:
We investigate both analytically and numerically a two-component ultracold atom system in one spatial dimension. The model features a tachyonic instability, which incorporates characteristic aspects of the mechanisms for particle production in early universe inflaton models. We establish a direct correspondence between measurable macroscopic growth rates for occupation numbers of the ultracold Bose gas and the underlying microscopic processes in terms of Feynman loop diagrams. We analyze several existing ultracold atom setups featuring dynamical instabilities and propose optimized protocols for their experimental realization. We demonstrate that relevant dynamical processes can be enhanced using a seeding procedure for unstable modes and clarify the role of initial quantum fluctuations and the generation of a nonlinear secondary stage for the amplification of modes.
T. V. Zache, V. Kasper, and J. Berges: Inflationary preheating dynamics with two-species condensates, New J. Phys. 19 (2017) 023030
https://doi.org/10.1103/PhysRevA.95.063629
Related to Project A03, A04, A05, B03
Abstract:
We present the status of the chemical freeze-out, determined from fits of hadron yields with the statistical hadronization (thermal) model, with focus on the data at the LHC. A description of the yields of hadrons containing light quarks as well as the application of the model for the production of the J/ψ meson is presented. The implications for the QCD phase diagram are discussed.
A. Andronic, P. Braun-Munzinger, K. Redlich, J. Stachel: Hadron yields, the chemical freeze-out and the QCD phase diagram, J. Phys.: Conf. Ser. 779 (2017) 012012
https://doi.org/10.1088/1742-6596/779/1/012012
Related to Project C05
Abstract:
We experimentally and theoretically study the effect of the intraspecies scattering length onto the heteronuclear Efimov scenario, following up on our earlier observation of Efimov resonances in an ultracold Cs-Li mixture for negative [Pires et al., Phys. Rev. Lett. 112, 250404 (2014)] and positive Cs-Cs scattering length [Ulmanis et al., Phys. Rev. Lett. 117, 153201 (2016)]. Three theoretical models of increasing complexity are employed to quantify its influence on the scaling factor and the three-body parameter: a simple Born-Oppenheimer picture, a zero-range theory, and a spinless van der Waals model. These models are compared to Efimov resonances observed in an ultracold mixture of bosonic
13Cs and fermionic 6Li atoms close to two Cs-Li Feshbach resonances located at 843 G and 889 G, characterized by different sign and magnitude of the Cs-Cs interaction. By changing the sign and magnitude of the intraspecies scattering length different scaling behaviors of the three-body loss rate are identified, in qualitative agreement with theoretical predictions. The three-body loss rate is strongly influenced by the intraspecies scattering length.
S. Häfner, J. Ulmanis, E.D. Kuhnle, Y. Wang, C.H. Greene, M. Weidemüller: Role of the intraspecies scattering length in the Efimov scenario with large mass difference, Phys. Rev. A 95 (2017) 062708
https://doi.org/10.1103/PhysRevA.95.062708
Related to Project C03
Abstract:
We present a versatile laser system which provides more than 1.5 W of narrowband light, tunable in the range from 455–463 nm. It consists of a commercial titanium-sapphire laser which is frequency doubled using resonant cavity second harmonic generation and stabilized to an external reference cavity. We demonstrate a wide wavelength tuning range combined with a narrow linewidth and low intensity noise. This laser system is ideally suited for atomic physics experiments such as two-photon excitation of Rydberg states of potassium atoms with principal quantum numbers n > 18. To demonstrate this we perform two-photon spectroscopy on ultracold potassium gases in which we observe an electromagnetically induced transparency resonance corresponding to the 35s1/2 state and verify the long-term stability of the laser system. Additionally, by performing spectroscopy in a magneto-optical trap we observe strong loss features corresponding to the excitation of s, p, d and higher-l states accessible due to a small electric field.
A. Arias, S. Helmrich, C. Schweiger, L. Ardizzone, G. Lochead, and S. Whitlock: Versatile, high-power 460 nm laser system for Rydberg excitation of ultracold potassium, Opt. Express 25 (2017) 14829
https://doi.org/10.1364/OE.25.014829
Related to Project A05
Abstract:
We report on the precise measurement of the atomic mass of a single proton with a purpose-built Penning-trap system. With a precision of 32 parts per trillion our result not only improves on the current CODATA literature value by a factor of 3, but also disagrees with it at a level of about 3 standard deviations.
F. Heiße, F. Köhler-Langes, S. Rau, J. Hou, S. Junck, A. Kracke, A. Mooser, W. Quint, S. Ulmer, G.Werth, K. Blaum, S. Sturm: High-Precision Measurement of the Proton’s Atomic Mass, Phys. Rev. Lett. 119 (2017) 033001
https://doi.org/10.1103/PhysRevLett.119.033001
Related to Project B01
Abstract:
Controllable arrays of ions and ultracold atoms can simulate complex many-body phenomena and may provide insights into unsolved problems in modern science. To this end, experimentally feasible protocols for quantifying the buildup of quantum correlations and coherence are needed, as performing full state tomography does not scale favourably with the number of particles. Here we develop and experimentally demonstrate such a protocol, which uses time reversal of the many-body dynamics to measure out-of-time-order correlation functions (OTOCs) in a long-range Ising spin quantum simulator with more than 100 ions in a Penning trap. By measuring a family of OTOCs as a function of a tunable parameter we obtain fine-grained information about the state of the system encoded in the multiple quantum coherence spectrum, extract the quantum state purity, and demonstrate the buildup of up to 8-body correlations. Future applications of this protocol could enable studies of many-body localization, quantum phase transitions, and tests of the holographic duality between quantum and gravitational systems.
M. Gärttner, J. G. Bohnet, A. Safavi-Naini, M. L. Wall, J. J. Bollinger, A. M. Rey: Measuring out-of-time-order correlations and multiple quantum spectra in a trapped-ion quantum magnet, Nat. Phys. 13 (2017) 781
https://www.nature.com/articles/nphys4119
Related to Project A05
Abstract:
Open and hidden heavy-flavor physics in high-energy nuclear collisions are entering a new and exciting stage towards reaching a clearer understanding of the new experimental results with the possibility to link them directly to the advancement in lattice Quantum Chromo-Dynamics (QCD). Recent results from experiments and theoretical developments regarding open and hidden heavy-flavor dynamics have been debated at the Lorentz Workshop Tomography of the Quark-Gluon Plasma with Heavy Quarks, which was held in October 2016 in Leiden, The Netherlands. In this contribution, we summarize identified common understandings and developed strategies for the upcoming five years, which aim at achieving a profound knowledge of the dynamical properties of the quark-gluon plasma.
G. Aarts et al.: Heavy-flavor production and medium properties in high-energy nuclear collisions – What next?, Eur. Phys. J. A 53 (2017) 93
https://doi.org/10.1140/epja/i2017-12282-9
Related to Project A01, A02, C05
Abstract:
We investigate strongly correlated non-Abelian plasmas out of equilibrium. Based on numerical simulations, we establish a self-similar scaling property for the time evolution of spatial Wilson loops that characterizes a universal state of matter far from equilibrium. Most remarkably, it exhibits a generalized area law which holds for a sufficiently large ratio of spatial area and fractional power of time. Performing calculations also for the perturbative regime at higher momenta, we are able to characterize the full nonthermal scaling properties of SU(2) and SU(3) symmetric plasmas from short to large distance scales in terms of two independent universal exponents and associated scaling functions.
J. Berges, M. Mace, S. Schlichting: Universal Self-Similar Scaling of Spatial Wilson Loops Out of Equilibrium, New J. Phys. 19 (2017) 023030
https://doi.org/10.1103/PhysRevLett.118.192005
Related to Project A01, B03, C05
Abstract:
Recent classical-statistical numerical simulations have established the “bottom-up” thermalization scenario of Baier et al. [Phys. Lett. B 502, 51 (2001)] as the correct weak coupling effective theory for thermalization in ultrarelativistic heavy-ion collisions. We perform a parametric study of photon production in the various stages of this bottom-up framework to ascertain the relative contribution of the off-equilibrium “glasma” relative to that of a thermalized quark-gluon plasma. Taking into account the constraints imposed by the measured charged hadron multiplicities at Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC), we find that glasma contributions are important especially for large values of the saturation scale at both energies. These nonequilibrium effects should therefore be taken into account in studies where weak coupling methods are employed to compute photon yields.
J. Berges, K. Reygers, N. Tanji, R. Venugopalan: Parametric estimate of the relative photon yields from the glasma and the quark-gluon plasma in heavy-ion collisions, Phys. Rev. C 95 (2017) 054904
https://doi.org/10.1103/PhysRevC.95.054904
Related to Project A01, A02, B03, C06
Abstract:
We explore the far-from-equilibrium dynamics of Bose gases in a universal regime associated to nonthermal fixed points. While previous investigations concentrated on scaling functions and exponents describing equal-time correlations, we compute the additional scaling functions and dynamic exponent z characterizing the frequency dependence or dispersion from unequal-time correlations. This allows us to compare the characteristic condensation and correlation times from a finite-size scaling analysis depending on the system’s volume.
A. Schachner, A. Piñeiro Orioli, J. Berges: Universal scaling of unequal-time correlation
functions in ultracold Bose gases far from equilibrium, Phys. Rev. A 95 (2017) 053605
https://doi.org/10.1103/PhysRevA.95.053605
Related to Project A01, A02, A03, A04, A05, B03
A. Dainese et al. (P. Braun-Munzinger, S. Masciocchi, J. Stachel): Heavy ions at the Future Circular Collider, CERN Yellow Report (2017) 635
Related to Project A01, A02, C05
K. Blaum, S. Sturm, S. Ulmer: In die Falle gegangen, Physik Journal 16 (2017) 31
http://hdl.handle.net/11858/00-001M-0000-002C-83D2-1
Related to Project B01
Abstract:
We measure the transport properties of two-dimensional ultracold Fermi gases during transverse demagnetization in a magnetic field gradient. Using a phase-coherent spin-echo sequence, we are able to distinguish bare spin diffusion from the Leggett-Rice effect, in which demagnetization is slowed by the precession of a spin current around the local magnetization. When the two-dimensional scattering length is tuned to be comparable to the inverse Fermi wave vector k−1F, we find that the bare transverse spin diffusivity reaches a minimum of 1.7(6) ℏ/m, where m is the bare particle mass. The rate of demagnetization is also reflected in the growth rate of the s-wave contact, observed using time-resolved spectroscopy. The contact rises to 0.28(3) k2F per particle, which quantifies how scaling symmetry is broken by near-resonant interactions, unlike in unitary three-dimensional systems. Our observations support the conjecture that, in systems with strong scattering, the local relaxation rate is bounded from above by kBT/ℏ.
C. Luciuk, S. Smale, F. Böttcher, H. Sharum, B. A. Olsen, S. Trotzky, T. Enss, J. H. Thywissen: Observation of Quantum-Limited Spin Transport in Strongly Interacting Two-Dimensional Fermi Gases, Phys. Rev. Lett. 118 (2017) 130405
https://doi.org/10.1103/PhysRevLett.118.130405
Related to Project C02, C03
Abstract:
We improve and extend our study of the complex in-medium heavy-quark potential and its Debye mass mD in a gluonic medium with a finer scan around the deconfinement transition and newly generated ensembles closer to the thermodynamic limit. On the lattices with larger physical volume, Re[V] shows signs of screening, i.e. a finite mD , only in the deconfined phase, reminiscent of a genuine phase transition. Consistently Im[V] exhibits nonzero values also only above TC . We compare the behavior of Re[V] with the color singlet free energies that have been used historically to extract the Debye mass. An effective coupling constant is computed to assess the residual influence of the confining part of the potential at T>0. Our previous finding of a gradual screening of Re[V] around TC on finer lattices is critically reassessed and interpreted to originate from finite volume artifacts. We discuss that deficiency of the β=7, ξb=3.5 parameter set at Ns=32, which has been in deployed in the literature before.
Y. Burnier, A. Rothkopf: Complex heavy-quark potential and Debye mass in a gluonic medium from lattice QCD, Phys. Rev. D 95 (2017) 054511
https://doi.org/10.1103/PhysRevD.95.054511
Related to Project C05
Abstract:
The concept of a screening mass is a powerful tool to simplify the intricate physics of in-medium test charges surrounded by light charge carriers. While it has been successfully used to describe electromagnetic properties, its definition and computation in QCD is plagued by questions of gauge invariance and the presence of non-perturbative contributions from the magnetic sector. Here we present a recent alternative definition of a gauge invariant Debye mass parameter following closely the original idea of Debye and H\”uckel. Our test charges are a static heavy quark-antiquark pair whose complex potential and its in-medium modification can be extracted using lattice QCD. By combining in a generalized Gauss-Law the non-perturbative aspects of quark binding with a perturbative ansatz for the medium effects, we succeed to describe the lattice values of the potential with a single temperature dependent parameter, in turn identified with a Debye mass. We find that its behavior, as evaluated in a recent quenched lattice QCD study, deviates from that in other approaches, such as hard-thermal-loop perturbation theory or from electric field correlators on the lattice. In particular around the phase transition its values tend to zero significantly faster than at weak-coupling.
A. Rothkopf, Y. Burnier: A gauge invariant Debye mass for the complex heavy-quark potential, PoS LATTICE2016 (2016) 028
https://doi.org/10.22323/1.256.0028
Related to Project C05
Abstract:
We present a real-time lattice approach to study the nonequilibrium dynamics of vector and axial charges in
SU(N)×U(1) gauge theories. Based on a classical description of the non-Abelian and Abelian gauge fields, we include dynamical fermions and develop operator definitions for (improved) Wilson and overlap fermions that allow us to study real-time manifestations of the axial anomaly from first principles. We present a first application of this approach to anomalous transport phenomena such as the chiral magnetic effect (CME) and the chiral separation effect (CSE) by studying the dynamics of fermions during and after a
SU(N) sphaleron transition in the presence of a U(1) magnetic field. We investigate the fermion mass and magnetic field dependence of the suggested signatures of the CME and the CSE and point out some important aspects which need to be accounted for in the macroscopic description of anomalous transport phenomena.
M. Mace, N. Müller, S. Schlichting, S. Sharma: Non-equilibrium study of the Chiral Magnetic Effect from real-time simulations with dynamical fermions, Phys.Rev. D 95 (2017) 036023
https://doi.org/10.1103/PhysRevD.95.036023
Related to Project A01
Abstract:
In this work, we present the first results on vector- and axial-vector meson spectral functions as obtained by applying the nonperturbative functional renormalization group approach to an effective low-energy theory motivated by the gauged linear sigma model. By using a recently proposed analytic continuation method, we study the in-medium behavior of the spectral functions of the ρ and a1 mesons in different regimes of the phase diagram. In particular, we demonstrate explicitly how these spectral functions degenerate at high temperatures as well as at large chemical potentials, as a consequence of the restoration of chiral symmetry. In addition, we also compute the momentum dependence of the ρ and a1 spectral functions and discuss the various timelike and spacelike processes that can occur.
C. Jung, F. Rennecke, R.-A. Tripolt, L. von Smekal, J. Wambach: In-medium spectral functions of vector- and axial-vector mesons from the functional renormalization group, Phys. Rev. D 95 (2017) 036020
https://doi.org/10.1103/PhysRevD.95.036020
Related to Project C06
Abstract:
Quantum systems in extreme conditions can exhibit universal behavior far from equilibrium associated to nonthermal fixed points with a wide range of topical applications from early-Universe inflaton dynamics and heavy-ion collisions to strong quenches in ultracold quantum gases. So far, most studies have relied on a mapping of the quantum dynamics onto a classical-statistical theory that can be simulated on a computer. However, the mapping is based on a weak-coupling limit, while phenomenological applications often require moderate interaction strengths. We report on the observation of nonthermal fixed points directly in quantum field theory beyond the weak-coupling limit. For the example of a relativistic scalar O(N)-symmetric quantum field theory, we numerically solve the nonequilibrium dynamics employing a 1/N expansion to next-to-leading order, which does not rely on a small coupling parameter. Starting from two different sets of overoccupied and of strong-field initial conditions, we find that nonthermal fixed points are not restricted to parameter ranges suitable for classical-statistical simulations but extend also to couplings of order 1. While the infrared behavior is found to be insensitive to the differences in the initial conditions, we demonstrate that transport phenomena to higher momenta depend on the presence or absence of a symmetry-breaking field expectation value.
J. Berges, B. Wallisch: Nonthermal Fixed Points in Quantum Field Theory Beyond the Weak-Coupling Limit, Phys. Rev. D 95 (2017) 036016
https://doi.org/10.1103/PhysRevD.95.036016
Related to Project A01, A03, A04, A05, B03
Abstract:
We discuss the experimental engineering of model systems for the description of quantum electrodynamics (QED) in one spatial dimension via a mixture of bosonic 23Na and fermionic 6Li atoms. The local gauge symmetry is realized in an optical superlattice, using heteronuclear boson–fermion spin-changing interactions which preserve the total spin in every local collision. We consider a large number of bosons residing in the coherent state of a Bose–Einstein condensate on each link between the fermion lattice sites, such that the behavior of lattice QED in the continuum limit can be recovered. The discussion about the range of possible experimental parameters builds, in particular, upon experiences with related setups of fermions interacting with coherent samples of bosonic atoms. We determine the atomic system’s parameters required for the description of fundamental QED processes, such as Schwinger pair production and string breaking. This is achieved by benchmark calculations of the atomic system and of QED itself using functional integral techniques. Our results demonstrate that the dynamics of one-dimensional QED may be realized with ultracold atoms using state-of-the-art experimental resources. The experimental setup proposed may provide a unique access to longstanding open questions for which classical computational methods are no longer applicable.
V. Kasper, F. Hebenstreit, F. Jendrzejewski, M. K. Oberthaler, J. Berges: Implementing quantum electrodynamics with ultracold atomic systems, New J. Phys. 19 (2017) 023030
https://iopscience.iop.org/article/10.1088/1367-2630/aa54e0/meta
Related to Project A01, B03, B04
Abstract:
We develop methods to deal with non-dynamical contributions to event-by-event fluctuation measurements of net-particle numbers in relativistic nuclear collisions. These contributions arise from impact parameter fluctuations and from the requirement of overall net-baryon number or net-charge conservation and may mask the dynamical fluctuations of interest, such as those due to critical endpoints in the QCD phase diagram. Within a model of independent particle sources we derive formulae for net-particle fluctuations and develop a rigorous approach to take into account contributions from participant fluctuations in realistic experimental environments and at any cumulant order. Interestingly, contributions from participant fluctuations to the second and third cumulants of net-baryon distributions are found to vanish at mid-rapidity for LHC energies while higher cumulants of even order are non-zero even when the net-baryon number at mid-rapidity is zero. At lower beam energies the effect of participant fluctuations increases and induces spurious higher moments. The necessary corrections become large and need to be carefully taken into account before comparison to theory. We also provide a procedure for selecting the optimal phase–space coverage of particles for fluctuation analyses and discuss quantitatively the necessary correction due to global charge conservation.
P. Braun-Munzinger, A. Rustamov, J. Stachel: Bridging the gap between event-by-event fluctuation measurements and theory predictions in relativistic nuclear collisions, Nucl. Phys. A 960 (2017) 114
https://doi.org/10.1016/j.nuclphysa.2017.01.011
Related to Project A01, A03, A04, C05, C06
Abstract:
Scaling solutions for the effective action in dilaton quantum gravity are investigated within the functional renormalization group approach. We find numerical solutions that connect ultraviolet and infrared fixed points as the ratio between scalar field and renormalization scale k is varied. In the Einstein frame the quantum effective action corresponding to the scaling solutions becomes independent of k.
The field equations derived from this effective action can be used directly for cosmology. Scale symmetry is spontaneously broken by a non-vanishing cosmological value of the scalar field. For the cosmology corresponding to our scaling solutions, inflation arises naturally. The effective cosmological constant becomes dynamical and vanishes asymptotically as time goes to infinity.
T. Henz, J. M. Pawlowski, C. Wetterich: Scaling solutions for Dilaton Quantum Gravity, Phys. Lett. B 769 (2017) 105
https://doi.org/10.1016/j.physletb.2017.01.057
Related to Project B01
Abstract:
We present a versatile laser system which provides more than 1.5 W of narrowband light, tunable in the range from 455–463 nm. It consists of a commercial titanium-sapphire laser which is frequency doubled using resonant cavity second harmonic generation and stabilized to an external reference cavity. We demonstrate a wide wavelength tuning range combined with a narrow linewidth and low intensity noise. This laser system is ideally suited for atomic physics experiments such as two-photon excitation of Rydberg states of potassium atoms with principal quantum numbers n > 18. To demonstrate this we perform two-photon spectroscopy on ultracold potassium gases in which we observe an electromagnetically induced transparency resonance corresponding to the 35s1/2 state and verify the long-term stability of the laser system. Additionally, by performing spectroscopy in a magneto-optical trap we observe strong loss features corresponding to the excitation of s, p, d and higher-l states accessible due to a small electric field.
S. Benić, K. Fukushima, O. Garcia-Montero, R. Venugopalan: Probing gluon saturation with next-to-leading order photon production at central rapidities in proton-nucleus collisions, J. High Energ. Phys. (2017) 115
https://doi.org/10.1007/JHEP01(2017)115
Related to Project B03
Abstract:
Following an approach of Matarrese and Pietroni, we derive the functional renormalization group (RG) flow of the effective action of cosmological large-scale structures. Perturbative solutions of this RG flow equation are shown to be consistent with standard cosmological perturbation theory. Non-perturbative approximate solutions can be obtained by truncating the a priori infinite set of possible effective actions to a finite subspace. Using for the truncated effective action a form dictated by dissipative fluid dynamics, we derive RG flow equations for the scale dependence of the effective viscosity and sound velocity of non-interacting dark matter, and we solve them numerically. Physically, the effective viscosity and sound velocity account for the interactions of long-wavelength fluctuations with the spectrum of smaller-scale perturbations. We find that the RG flow exhibits an attractor behaviour in the IR that significantly reduces the dependence of the effective viscosity and sound velocity on the input values at the UV scale. This allows for a self-contained computation of matter and velocity power spectra for which the sensitivity to UV modes is under control.
S. Floerchinger, M. Garny, N. Tetradis, U. A. Wiedemann: Renormalization-group flow of the effective action of cosmological large-scale structures, JCAP (2017) 048
https://iopscience.iop.org/article/10.1088/1475-7516/2017/01/048
Related to Project C06
Abstract:
We investigate baryon number fluctuations for finite temperature and density in two-flavor QCD. This is done within a QCD-improved low-energy effective theory in an extension of the approach put forward by Fu and Pawlowski [Phys. Rev. D 92, 116006 (2015) and Phys. Rev. D 93, 091501 (2016)]. In the present work, we aim to improve the predictive power of this approach for large temperatures and, in partitular, large densities, that is, for small collision energies. This is achieved by taking into account the full frequency dependence of the quark dispersion. This ensures the necessary Silver Blaze property of finite density QCD for the first time, which so far was only implemented approximately. Moreover, we show that Polyakov-loop fluctuations have a sizeable impact at large temperatures and density. The results for the kurtosis of baryon number fluctuations are compared to previous effective theory results, lattice results, and recent experimental data from STAR.
Wei-jie Fu, Jan M. Pawlowski, Fabian Rennecke, and Bernd-Jochen Schaefer: Baryon number fluctuations at finite temperature and density, Phys. Rev. D 94 (2016) 116020
https://doi.org/10.1103/PhysRevD.94.116020
Related to Project A02, C05, C06
Abstract:
In contrast to classical empty space, the quantum vacuum fundamentally alters the properties of embedded particles. This paradigm shift allows one to explain the discovery of the celebrated Lamb shift in the spectrum of the hydrogen atom. Here, we engineer a synthetic vacuum, building on the unique properties of ultracold atomic gas mixtures, offering the ability to switch between empty space and quantum vacuum. Using high-precision spectroscopy, we observe the phononic Lamb shift, an intriguing many-body effect originally conjectured in the context of solid-state physics. We find good agreement with theoretical predictions based on the Fröhlich model. Our observations establish this experimental platform as a new tool for precision benchmarking of open theoretical challenges, especially in the regime of strong coupling between the particles and the quantum vacuum.
T. Rentrop, A. Trautmann, F. A. Olivares, F. Jendrzejewski, A. Komnik, and M. K. Oberthaler: Observation of the Phononic Lamb Shift with a Synthetic Vacuum, Phys. Rev. X 6 (2016) 041041
https://doi.org/10.1103/PhysRevX.6.041041
Related to Project A04, B04
Abstract:
Doppler backscattering of optical laser photons on a “flying mirror” of relativistic electrons promises to yield coherent photons with MeV-range energies. We compare the nuclear interaction of such a laser pulse with the standard atom-laser interaction. The mean-field description of atoms must be replaced by a rate equation and the classical field strength, far too faint in nuclei, by the dipole transition rate. Significant nuclear excitation occurs for photon numbers much smaller than typical for atoms. That drastically reduces the requirements on the experimental realization of a “flying mirror”.
Adriana Pálffy, Paul-Gerhard Reinhard, Hans A. Weidenmüller: Laser-Matter Interaction: Classical Regime versus Quantum Regime, arXiv:1611.06811
https://arxiv.org/abs/1611.06811
Related to Project B02
Abstract:
We investigate theoretically and experimentally the heteronuclear Efimov scenario for a three-body system that consists of two bosons and one distinguishable particle with positive intraspecies scattering lengths. The three-body parameter at the three-body scattering threshold and the scaling factor between consecutive Efimov resonances are found to be controlled by the scattering length between the two bosons, approximately independent of short-range physics. We observe two excited-state Efimov resonances in the three-body recombination spectra of an ultracold mixture of fermionic 6Li and bosonic 133Cs atoms close to a Li-Cs Feshbach resonance, where the Cs-Cs interaction is positive. Deviation of the obtained scaling factor of 4.0(3) from the universal prediction of 4.9 and the absence of the ground state Efimov resonance shed new light on the interpretation of the universality and the discrete scaling behavior of heteronuclear Efimov physics.
Juris Ulmanis, Stephan Häfner, Rico Pires, Eva D. Kuhnle, Yujun Wang, Chris H. Greene, and Matthias Weidemüller: Heteronuclear Efimov Scenario with Positive Intraspecies Scattering Length, Phys. Rev. Lett. 117 (2016) 153201
https://doi.org/10.1103/PhysRevLett.117.153201
Related to Project C03
Abstract:
The muonic vacuum polarization contribution to the g-factor of the electron bound in a nuclear potential is investigated theoretically. The electric as well as the magnetic loop contributions are evaluated. We found these muonic effects to be observable in planned trapped-ion experiments with light and medium-heavy highly charged ions. The enhancement due to the strong Coulomb field boosts these contributions much above the corresponding terms in the free-electron g-factor. Due to their magnitude, muonic vacuum polarization terms are also significant in planned determinations of the fine-structure constant from the bound-electron g-factor.
N. A. Belov, B. Sikora, R. Weis, V. A. Yerokhin, S. Sturm, K. Blaum, C. H. Keitel, Z. Harman: Muonic vacuum polarization correction to the bound-electron g-factor, arXiv:2003.10338, 2020.
https://arxiv.org/abs/1610.01340
Related to Project B02, B01
Abstract:
We present a first-principles study of anomaly induced transport phenomena by performing real-time lattice simulations with dynamical fermions coupled simultaneously to non-Abelian SU(Nc) and Abelian U(1)gauge fields. Investigating the behavior of vector and axial currents during a sphaleron transition in the presence of an external magnetic field, we demonstrate how the interplay of the chiral magnetic and chiral separation effect leads to the formation of a propagating wave. We further analyze the dependence of the magnitude of the induced vector current and the propagation of the wave on the amount of explicit chiral symmetry breaking due to finite quark masses.
Niklas Müller, Sören Schlichting, and Sayantan Sharma: Anomaly-Induced Dynamical Refringence in Strong-Field QED, Phys. Rev. Lett. 117 (2016) 142301
https://doi.org/10.1103/PhysRevLett.117.142301
Related to Project A01
Abstract:
The analytic continuation from the Euclidean domain to real space of the one-particle irreducible quantum effective action is discussed in the context of generalized local equilibrium states. Discontinuous terms associated with dissipative behavior are parametrized in terms of a conveniently defined sign operator. A generalized variational principle is then formulated, which allows to obtain causal and real dissipative equations of motion from the analytically continued quantum effective action. Differential equations derived from the implications of general covariance determine the space-time evolution of the temperature and fluid velocity fields and allow for a discussion of entropy production including a local form of the second law of thermodynamics.
S. Floerchinger: Variational principle for theories with dissipation from analytic continuation, JHEP 1609 (2016) 099
https://doi.org/10.1007/JHEP09(2016)099
Related to Project C06
Abstract:
We consider a system of ultracold atoms in an optical lattice as a quantum simulator for electron–positron pair production in quantum electrodynamics (QED). For a setup in one spatial dimension, we investigate the nonequilibrium phenomenon of pair production including the backreaction leading to plasma oscillations. Unlike previous investigations on quantum link models, we focus on the infinite-dimensional Hilbert space of QED and show that it may be well approximated by experiments employing Bose–Einstein condensates interacting with fermionic atoms. Numerical calculations based on functional integral techniques give a unique access to the physical parameters required to realize QED phenomena in a cold atom experiment. In particular, we use our approach to consider quantum link models in a yet unexplored parameter regime and give bounds for their ability to capture essential features of the physics. The results suggest a paradigmatic change towards realizations using coherent many-body states for quantum simulations of high-energy particle physics phenomena.
V. Kasper, F. Hebenstreit, M. K. Oberthaler, J. Berges: Schwinger pair production with ultracold atoms, Phys. Lett. B 760 (2016) 742
https://doi.org/10.1016/j.physletb.2016.07.036
Related to Project A01, B04
Abstract:
We investigate Landau gauge SU(3) Yang-Mills theory in a systematic vertex expansion scheme for the effective action with the functional renormalization group. Particular focus is put on the dynamical creation of the gluon mass gap at nonperturbative momenta and the consistent treatment of quadratic divergences. The nonperturbative ghost and transverse gluon propagators as well as the momentum-dependent ghost-gluon, three-gluon and four-gluon vertices are calculated self-consistently with the classical action as the only input. The apparent convergence of the expansion scheme is discussed and within the errors, our numerical results are in quantitative agreement with available lattice results.
Anton K. Cyrol, Leonard Fister, Mario Mitter, Jan M. Pawlowski, and Nils Strodthoff: Landau gauge Yang-Mills correlation functions, Phys. Rev. D 94 (2016) 054005
https://doi.org/10.1103/PhysRevD.94.054005
Related to Project A02, B03, C05
Abstract:
We investigate the impact of the Adler-Bell-Jackiw anomaly on the nonequilibrium evolution of strong-field quantum electrodynamics (QED) using real-time lattice gauge theory techniques. For field strengths exceeding the Schwinger limit for pair production, we encounter a highly absorptive medium with anomaly induced dynamical refractive properties. In contrast to earlier expectations based on equilibrium properties, where net anomalous effects vanish because of the trivial vacuum structure, we find that out-of-equilibrium conditions can have dramatic consequences for the presence of quantum currents with distinctive macroscopic signatures. We observe an intriguing tracking behavior, where the system spends longest times near collinear field configurations with maximum anomalous current. Apart from the potential relevance of our findings for future laser experiments, similar phenomena related to the chiral magnetic effect are expected to play an important role for strong QED fields during initial stages of heavy-ion collision experiments.
N. Mueller, F. Hebenstreit, and J. Berges: Anomaly-Induced Dynamical Refringence in Strong-Field QED, Phys. Rev. Lett. 117 (2016) 061601
https://doi.org/10.1103/PhysRevLett.117.061601
Related to Project A01, B04
Abstract:
We experimentally demonstrate a nonlinear detection scheme exploiting time-reversal dynamics that disentangles continuous variable entangled states for feasible readout. Spin-exchange dynamics of Bose-Einstein condensates is used as the nonlinear mechanism which not only generates entangled states but can also be time reversed by controlled phase imprinting. For demonstration of a quantum-enhanced measurement we construct an active atom SU(1,1) interferometer, where entangled state preparation and nonlinear readout both consist of parametric amplification. This scheme is capable of exhausting the quantum resource by detecting solely mean atom numbers. Controlled nonlinear transformations widen the spectrum of useful entangled states for applied quantum technologies.
D. Linnemann, H. Strobel, W. Muessel, J. Schulz, R. J. Lewis-Swan, K. V. Kheruntsyan, and M. K. Oberthaler: Quantum-Enhanced Sensing Based on Time Reversal of Nonlinear Dynamics, Phys. Rev. Lett. 117 (2016) 013001
https://doi.org/10.1103/PhysRevLett.117.013001
Related to Project A04
Abstract:
We review the recent progress in the understanding of the relaxation of isolated near-integrable quantum many-body systems. Focusing on prethermalization and universal dynamics following a quench, we describe the experiments with ultracold atomic gases that illustrate these phenomena and summarize the essential theoretical concepts employed to interpret them. Our discussion highlights the key topics that link the different approaches to this interdisciplinary field, including the generalized Gibbs ensemble, non-thermal fixed points, critical slowing and universal scaling. Finally, we point to new experimental challenges demonstrating these fundamental features of many-body quantum systems out of equilibrium.
T. Langen, T. Gasenzer, J. Schmiedmayer: Prethermalization and universal dynamics in near-integrable quantum systems, J. of Stat. Mech. 06 (2016) 064009
https://doi.org/10.1088/1742-5468/2016/06/064009
Related to Project A03
Abstract:
Depending on the material and edge under consideration, core level spectra manifest themselves as local excitons with multiplets, edge singularities, resonances, or the local projected density of states. Both extremes, i.e., local excitons and non-interacting delocalized excitations are theoretically well under control. Describing the intermediate regime, where local many body interactions and band-formation are equally important is a challenge. Here we discuss how Quanty, a versatile quantum many body script language, can be used to calculate a variety of different core level spectroscopy types on solids and molecules, both in the frequency as well as the time domain. The flexible nature of Quanty allows one to choose different approximations for different edges and materials. For example, using a newly developed method merging ideas from density renormalization group and quantum chemistry [1-3], Quanty can calculate excitons, resonances and band-excitations in x-ray absorption, photoemission, x-ray emission, fluorescence yield, non-resonant inelastic x-ray scattering, resonant inelastic x-ray scattering and many more spectroscopy types. Quanty can be obtained from: http://www.quanty.org.
M. W. Haverkort: Quanty for core level spectroscopy – excitons, resonances and band excitations in time and frequency domain, J. Phys.: Conf. Ser. 712 (2016) 012001
https://doi.org/10.1088/1742-6596/712/1/012001
Related to Project B01, C01
Abstract:
We present the new nCTEQ15 set of nuclear parton distribution functions (PDFs) with uncertainties. This fit extends the CTEQ proton PDFs to include the nuclear dependence using data on nuclei all the way up to 208Pb. The uncertainties are determined using the Hessian method with an optimal rescaling of the eigenvectors to accurately represent the uncertainties for the chosen tolerance criteria. In addition to the deep inelastic scattering and Drell-Yan processes, we also include inclusive pion production data from the Relativistic Heavy Ion Collider to help constrain the nuclear gluon PDF. Furthermore, we investigate the correlation of the data sets with specific nuclear PDF flavor components and asses the impact of individual experiments. We also provide comparisons of the nCTEQ15 set with recent fits from other groups.
K. Kovařík, A. Kusina, T. Ježo, D. B. Clark, C. Keppel, F. Lyonnet, J. G. Morfín, F. I. Olness, J. F. Owens, I. Schienbein, and J. Y. Yu: nCTEQ15: Global analysis of nuclear parton distributions with uncertainties in the CTEQ framework, Phys. Rev. D 93 (2016) 085037
https://doi.org/10.1103/PhysRevD.93.085037
Related to Project C05
Abstract:
The Efimov scenario is a universal three-body effect addressing many areas of modern quantum physics. It plays an important role in the transition between few- and many-body physics and has enabled important breakthroughs in the understanding of the universal few-body theory. We review the basic concepts of the Efimov scenario with specific emphasis on the similarities and differences between homonuclear and heteronuclear systems. In the latter scenario, the existence of a second, independently tunable interaction parameter enables novel few-body phenomena that are universal and have no counterexamples in the homonuclear case. We discuss recent experimental approaches using ultracold atomic gases with magnetically tunable interactions and elucidate the role of short-range interactions in the emergence of universal and non-universal behavior.
Juris Ulmanis, Stephan Häfner, Eva D. Kuhnle, and Matthias Weidemüller: Heteronuclear Efimov resonances in ultracold quantum gases, National Science Review 3 (2016) 174
https://doi.org/10.1093/nsr/nww018
Related to Project C03
Abstract:
The magnetic moment μ of a bound electron, generally expressed by the g-factor μ=-g μB s ħ(-1) with μB the Bohr magneton and s the electron’s spin, can be calculated by bound-state quantum electrodynamics (BS-QED) to very high precision. The recent ultra-precise experiment on hydrogen-like silicon determined this value to eleven significant digits, and thus allowed to rigorously probe the validity of BS-QED. Yet, the investigation of one of the most interesting contribution to the g-factor, the relativistic interaction between electron and nucleus, is limited by our knowledge of BS-QED effects. By comparing the g-factors of two isotopes, it is possible to cancel most of these contributions and sensitively probe nuclear effects. Here, we present calculations and experiments on the isotope dependence of the Zeeman effect in lithium-like calcium ions. The good agreement between the theoretical predicted recoil contribution and the high-precision g-factor measurements paves the way for a new generation of BS-QED tests.
F. Köhler, K. Blaum, M. Block, S. Chenmarev, S. Eliseev, D.A. Glazov, M. Goncharov, J. Hou, A. Kracke, D.A. Nesterenko, Y.N. Novikov, W. Quint, E. Minaya Ramirez, V.M. Shabaev, S. Sturm, A.V. Volotka, G. Werth: Isotope dependence of the Zeeman effect in lithium-like calcium, Nature Comm. 7 (2016) 10246
https://doi.org/10.1038/ncomms10246
Related to Project B01