The Experts below are selected from a list of 108051 Experts worldwide ranked by ideXlab platform
Fabian Senf - One of the best experts on this subject based on the ideXlab platform.
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nonequilibrium phase transitions in finite arrays of globally coupled stratonovich models strong Coupling Limit
New Journal of Physics, 2009Co-Authors: Fabian Senf, Philipp M Altrock, Ulrich BehnAbstract:A finite array of N globally coupled Stratonovich models exhibits a continuous nonequilibrium phase transition. In the Limit of strong Coupling, there is a clear separation of timescales of centre of mass and relative coordinates. The latter relax very fast to zero and the array behaves as a single entity described by the centre of mass coordinate. We compute analytically the stationary probability distribution and the moments of the centre of mass coordinate. The scaling behaviour of the moments near the critical value of the control parameter ac(N) is determined. We identify a crossover from linear to square root scaling with in- creasing distance fromac. The crossover point approachesac in the Limit N ! 1 which reproduces previous results for infinite arrays. Our results are obtained in both the Fokker-Planck and the Langevin approach and are corroborated by numerical simulations. For a general class of models we show that the transition manifold in the parameter space depends on N and is determined by the scaling behaviour near a fixed point of the stochastic flow.
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nonequilibrium phase transitions in finite arrays of globally coupled stratonovich models strong Coupling Limit
arXiv: Statistical Mechanics, 2009Co-Authors: Fabian Senf, Philipp M Altrock, Ulrich BehnAbstract:A finite array of $N$ globally coupled Stratonovich models exhibits a continuous nonequilibrium phase transition. In the Limit of strong Coupling there is a clear separation of time scales of center of mass and relative coordinates. The latter relax very fast to zero and the array behaves as a single entity described by the center of mass coordinate. We compute analytically the stationary probability and the moments of the center of mass coordinate. The scaling behaviour of the moments near the critical value of the control parameter $a_c(N)$ is determined. We identify a crossover from linear to square root scaling with increasing distance from $a_c$. The crossover point approaches $a_c$ in the Limit $N \to \infty$ which reproduces previous results for infinite arrays. The results are obtained in both the Fokker-Planck and the Langevin approach and are corroborated by numerical simulations. For a general class of models we show that the transition manifold in the parameter space depends on $N$ and is determined by the scaling behaviour near a fixed point of the stochastic flow.
Wolfgang Unger - One of the best experts on this subject based on the ideXlab platform.
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dual formulation and phase diagram of lattice qcd in the strong Coupling regime
EPJ Web of Conferences, 2018Co-Authors: Giuseppe Gagliardi, Wolfgang UngerAbstract:We present the computation of invariants that arise in the strong Coupling expansion of lattice QCD. These invariants are needed for Monte Carlo simulations of Lattice QCD with staggered fermions in a dual, color singlet representation. This formulation is in particular useful to tame the finite density sign problem. The gauge integrals in this Limiting case β → 0 are well known, but the gauge integrals needed to study the gauge corrections are more involved. We discuss a method to evaluate such integrals. The phase boundary of lattice QCD for staggered fermions in the μB – T plane has been established in the strong Coupling Limit. We present numerical simulations away from the strong Coupling Limit, taking into account the higher order gauge corrections via plaquette occupation numbers. This allows to study the nuclear and chiral transition as a function of β .
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dual formulation and phase diagram of lattice qcd in the strong Coupling regime
arXiv: High Energy Physics - Lattice, 2017Co-Authors: Giuseppe Gagliardi, Jangho Kim, Wolfgang UngerAbstract:We present the computation of invariants that arise in the strong Coupling expansion of lattice QCD. These invariants are needed for Monte Carlo simulations of Lattice QCD with staggered fermions in a dual, color singlet representation. This formulation is in particular useful to tame the finite density sign problem. The gauge integrals in this Limiting case $\beta\rightarrow 0$ are well known, but the gauge integrals needed to study the gauge corrections are more involved. We discuss a method to evaluate such integrals. The phase boundary of lattice QCD for staggered fermions in the $\mu_B-T$ plane has been established in the strong Coupling Limit. We present numerical simulations away from the strong Coupling Limit, taking into account the higher order gauge corrections via plaquette occupation numbers. This allows to study the nuclear and chiral transition as a function of $\beta$.
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lattice qcd phase diagram in and away from the strong Coupling Limit
Physical Review Letters, 2014Co-Authors: Philippe De Forcrand, Jens Langelage, Owe Philipsen, Wolfgang UngerAbstract:We study lattice QCD with four flavors of staggered quarks. In the Limit of infinite gauge Coupling, "dual" variables can be introduced, which render the finite-density sign problem mild and allow a full determination of the μ-T phase diagram by Monte Carlo simulations, also in the chiral Limit. However, the continuum Limit coincides with the weak Coupling Limit. We propose a strong-Coupling expansion approach towards the continuum Limit. We show first results, including the phase diagram and its chiral critical point, from this expansion truncated at next-to-leading order.
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towards corrections to the strong Coupling Limit of staggered lattice qcd
Proceedings of XXIX International Symposium on Lattice Field Theory — PoS(Lattice 2011), 2012Co-Authors: Michael Fromm, Wolfgang Unger, Jens Langelage, Philippe De Forcrand, Kotaroh Miura, Owe PhilipsenAbstract:We report on the first steps of an ongoing project to add gauge observables and gauge corrections to the well-studied strong Coupling Limit of staggered lattice QCD, which has been shown earlier to be amenable to numerical simulations by the worm algorithm in the chiral Limit and at finite density. Here we show how to evaluate the expectation value of the Polyakov loop in the framework of the strong Coupling Limit at finite temperature, allowing to study confinement properties along with those of chiral symmetry breaking. We find the Polyakov loop to rise smoothly, thus signalling deconfinement. The non-analytic nature of the chiral phase transition is reflected in the derivative of the Polyakov loop. We also discuss how to construct an effective theory for non-zero lattice Coupling, which is valid to O(β ).
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continuous time monte carlo for lattice qcd in the strong Coupling Limit
Journal of Physics G, 2011Co-Authors: Wolfgang Unger, Philippe De ForcrandAbstract:We present results for lattice QCD in the Limit of infinite gauge Coupling, obtained from a worm-type Monte Carlo algorithm on a discrete spatial lattice but with continuous Euclidean time. This is obtained by sending both the anisotropy parameter γ2 a/at and the number of time-slices Nτ to infinity, keeping the ratio γ2/Nτ aT fixed. The obvious gain is that no continuum extrapolation Nτ → ∞ has to be carried out. Moreover, the algorithm is faster and the sign problem disappears. We compare our computations with those on discrete lattices. We determine the phase diagram as a function of temperature and baryon chemical potential.
Hong Yao - One of the best experts on this subject based on the ideXlab platform.
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strong Coupling Limit of the holstein hubbard model
Physical Review Letters, 2020Co-Authors: Zhaoyu Han, Steven A Kivelson, Hong YaoAbstract:We analyze the quantum phase diagram of the Holstein-Hubbard model using an asymptotically exact strong Coupling expansion. We find all sorts of interesting phases including a pair-density wave, a charge 4e (and even a charge 6e) superconductor, regimes of phase separation, and a variety of distinct charge-density-wave, spin-density-wave, and superconducting regimes. We chart the crossovers that occur as a function of the degree of retardation, i.e., the ratio of characteristic phonon frequency to the strength of interactions.
Alexey Y Nikitin - One of the best experts on this subject based on the ideXlab platform.
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Boron nitride nanoresonators for phonon-enhanced molecular vibrational spectroscopy at the strong Coupling Limit
Light: Science & Applications, 2018Co-Authors: Marta Autore, Irene Dolado, Francisco J Alfaro-mozaz, Ruben Esteban, Ainhoa Atxabal, Fèlix Casanova, Luis E Hueso, Pablo Alonso-gonzález, Javier Aizpurua, Alexey Y NikitinAbstract:Infrared spectroscopy is a powerful tool for characterizing materials based on their specific vibrational fingerprints. However, its ability to characterize small amounts or thin layers of molecules is Limited by their extremely small infrared absorption cross-sections. This Limitation can be overcome by surface-enhanced infrared absorption spectroscopy (SEIRA), which exploits the field enhancement provided by plasmon polaritons on thin metal films or resonant metallic nanostructures. Now, Rainer Hillenbrand from CIC nanoGUNE in San Sebastián (Spain) and co-workers have developed highly sensitive phonon-polariton resonators for SEIRA detection, based on hexagonal boron nitride ribbons, which exhibit quality factors much higher than their plasmonic counterparts. They demonstrated phonon-enhanced molecular vibrational spectroscopy with sensitivity down to femtomolar levels, approaching the strong Coupling Limit. Enhanced light-matter interactions are the basis of surface-enhanced infrared absorption (SEIRA) spectroscopy, and conventionally rely on plasmonic materials and their capability to focus light to nanoscale spot sizes. Phonon polariton nanoresonators made of polar crystals could represent an interesting alternative, since they exhibit large quality factors, which go far beyond those of their plasmonic counterparts. The recent emergence of van der Waals crystals enables the fabrication of high-quality nanophotonic resonators based on phonon polaritons, as reported for the prototypical infrared-phononic material hexagonal boron nitride (h-BN). In this work we use, for the first time, phonon-polariton-resonant h-BN ribbons for SEIRA spectroscopy of small amounts of organic molecules in Fourier transform infrared spectroscopy. Strikingly, the interaction between phonon polaritons and molecular vibrations reaches experimentally the onset of the strong Coupling regime, while numerical simulations predict that vibrational strong Coupling can be fully achieved. Phonon polariton nanoresonators thus could become a viable platform for sensing, local control of chemical reactivity and infrared quantum cavity optics experiments.
Ulrich Behn - One of the best experts on this subject based on the ideXlab platform.
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nonequilibrium phase transitions in finite arrays of globally coupled stratonovich models strong Coupling Limit
New Journal of Physics, 2009Co-Authors: Fabian Senf, Philipp M Altrock, Ulrich BehnAbstract:A finite array of N globally coupled Stratonovich models exhibits a continuous nonequilibrium phase transition. In the Limit of strong Coupling, there is a clear separation of timescales of centre of mass and relative coordinates. The latter relax very fast to zero and the array behaves as a single entity described by the centre of mass coordinate. We compute analytically the stationary probability distribution and the moments of the centre of mass coordinate. The scaling behaviour of the moments near the critical value of the control parameter ac(N) is determined. We identify a crossover from linear to square root scaling with in- creasing distance fromac. The crossover point approachesac in the Limit N ! 1 which reproduces previous results for infinite arrays. Our results are obtained in both the Fokker-Planck and the Langevin approach and are corroborated by numerical simulations. For a general class of models we show that the transition manifold in the parameter space depends on N and is determined by the scaling behaviour near a fixed point of the stochastic flow.
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nonequilibrium phase transitions in finite arrays of globally coupled stratonovich models strong Coupling Limit
arXiv: Statistical Mechanics, 2009Co-Authors: Fabian Senf, Philipp M Altrock, Ulrich BehnAbstract:A finite array of $N$ globally coupled Stratonovich models exhibits a continuous nonequilibrium phase transition. In the Limit of strong Coupling there is a clear separation of time scales of center of mass and relative coordinates. The latter relax very fast to zero and the array behaves as a single entity described by the center of mass coordinate. We compute analytically the stationary probability and the moments of the center of mass coordinate. The scaling behaviour of the moments near the critical value of the control parameter $a_c(N)$ is determined. We identify a crossover from linear to square root scaling with increasing distance from $a_c$. The crossover point approaches $a_c$ in the Limit $N \to \infty$ which reproduces previous results for infinite arrays. The results are obtained in both the Fokker-Planck and the Langevin approach and are corroborated by numerical simulations. For a general class of models we show that the transition manifold in the parameter space depends on $N$ and is determined by the scaling behaviour near a fixed point of the stochastic flow.
