Fermion and gluon spectral functions far from equilibrium

Motivated by the quark-gluon plasma, we develop a simulation method to obtain the spectral function of (Wilson) fermions non-perturbatively in a non-Abelian gauge theory with large gluon occupation numbers [1]. We apply our method to a non-Abelian plasma close to its non-thermal fixed point, i.e., in a far-from-equilibrium self-similar regime, and find mostly very good agreement with perturbative hard loop (HTL) calculations. For the first time, we extract the full momentum dependence of the damping rate of fermionic collective excitations and compare our results to recent non-perturbative extractions of gluonic spectral functions in two and three spatial dimensions [2, 3].

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Experimental and Analytical Studies on Flexure Pivot Tilting Pad Gas Bearings With Dampers Applied to Radially Compliant Pads

Volume 6: Structures and Dynamics, Parts A and B ◽

10.1115/gt2009-59285 ◽

2009 ◽

Cited By ~ 1

Author(s):

Daejong Kim ◽

Aaron Rimpel

Keyword(s):

Simulation Method ◽

Analysis Tool ◽

Primary Analysis ◽

Successful Operation ◽

Gas Bearings ◽

Viscoelastic Dampers ◽

Thermal Growth ◽

Tilting Pad ◽

Rotor Bearing ◽

First Time

Hydrodynamic flexure pivot tilting pad gas bearings (FPTPGBs) can enable successful operation of oil-free microturbomachinery, and FPTPGBs with radially compliant pads (FPTPGB-Cs) permit rotor centrifugal and/or thermal growth to exceed original bearing clearances and achieve higher speeds. This work presents the experimental and analytical study of such bearings and the application of dampers behind the pad radial compliance structure. A time domain orbit simulation method was implemented as the primary analysis tool to predict rotor-bearing response to imbalance, the presence and location of critical speeds, etc., and compare with test results. Experiments demonstrate the stable hydrodynamic operation of FPTPGBs with a ∼28.6 mm, 0.8 kg rotor above 120 krpm for the first time. The rotor-bearing system was intentionally destabilized in tests by increasing bearing clearances, and viscoelastic dampers added behind the FPTPGB pads delayed the onset of subsynchronous vibrations (from 43 krpm without damper to above 50 krpm with damper). Midrange subsynchronous vibrations of the destabilized system initiated at ∼20 krpm were suppressed by ∼25 krpm due to the stabilizing effect of rotor centrifugal growth. The viscoelastic dampers had a negligible effect on suppressing these midrange subsynchronous vibrations in experiments, but this was not demonstrated in simulations, presumed to be due to much lower stiffness contribution of the damper at lower frequencies.

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Prescaling and far-from-equilibrium hydrodynamics in the quark-gluon plasma

Nuclear Physics A ◽

10.1016/j.nuclphysa.2020.121966 ◽

2021 ◽

Vol 1005 ◽

pp. 121966

Author(s):

Aleksas Mazeliauskas ◽

Jürgen Berges

Keyword(s):

Quark Gluon Plasma ◽

Gluon Plasma ◽

Far From Equilibrium

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Nonstationary stochastic simulation method for the risk assessment of water allocation

Environmental Science Water Research & Technology ◽

10.1039/d0ew00695e ◽

2021 ◽

Vol 7 (1) ◽

pp. 212-221

Author(s):

Shu Chen ◽

Jijun Xu ◽

Qingqing Li ◽

Yongqiang Wang ◽

Zhe Yuan ◽

...

Keyword(s):

Risk Assessment ◽

Stochastic Simulation ◽

Water Allocation ◽

Simulation Method ◽

First Time

It is the first time to consider the hydrological nonstationary in water allocation risk assessment.

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Experimental and Analytical Studies on Flexure Pivot Tilting Pad Gas Bearings With Dampers Applied to Radially Compliant Pads

Journal of Tribology ◽

10.1115/1.3201831 ◽

2009 ◽

Vol 131 (4) ◽

Cited By ~ 6

Author(s):

Aaron Rimpel ◽

Daejong Kim

Keyword(s):

Simulation Method ◽

Analysis Tool ◽

Primary Analysis ◽

Successful Operation ◽

Gas Bearings ◽

Viscoelastic Dampers ◽

Thermal Growth ◽

Tilting Pad ◽

Rotor Bearing ◽

First Time

Hydrodynamic flexure pivot tilting pad gas bearings (FPTPGBs) can enable successful operation of oil-free microturbomachinery and FPTPGBs with radially compliant pads permit rotor centrifugal and/or thermal growth to exceed original bearing clearances and achieve higher speeds. This work presents the experimental and analytical study of such bearings and the application of dampers behind the pad radial compliance structure. A time domain orbit simulation method was implemented as the primary analysis tool to predict the rotor-bearing response to imbalance, the presence and location of critical speeds, etc., and to compare with test results. Experiments demonstrate the stable hydrodynamic operation of FPTPGBs with an ∼28.6 mm, 0.8 kg rotor above 120 krpm, for the first time. The rotor-bearing system was intentionally destabilized in tests by increasing bearing clearances and the viscoelastic dampers added behind the FPTPGB pads delayed the onset of subsynchronous vibrations (from 43 krpm without damper to above 50 krpm with damper). Midrange subsynchronous vibrations of the destabilized system initiated at ∼20 krpm were suppressed by ∼25 krpm due to the stabilizing effect of rotor centrifugal growth. The viscoelastic dampers had a negligible effect on suppressing these midrange subsynchronous vibrations in experiments, but this was not demonstrated in simulations, presumed to be due to much lower stiffness contribution of the damper at lower frequencies.

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Gauge Invariance and Mass Gap in (2+1)-Dimensional Yang–Mills Theory

International Journal of Modern Physics A ◽

10.1142/s0217751x9700089x ◽

1997 ◽

Vol 12 (06) ◽

pp. 1161-1171 ◽

Cited By ~ 21

Author(s):

Dimitra Karabali ◽

V. P. Nair

Keyword(s):

Gauge Invariance ◽

Gauge Theories ◽

Abelian Gauge ◽

Gauge Invariant ◽

Yang Mills ◽

Mass Gap ◽

Spatial Dimensions

In terms of a gauge-invariant matrix parametrization of the fields, we give an analysis of how the mass gap could arise in non-Abelian gauge theories in two spatial dimensions.

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FLAVOR DEPENDENCE OF UNPOLARIZED TMDS FROM SEMI-INCLUSIVE PION PRODUCTION

International Journal of Modern Physics Conference Series ◽

10.1142/s2010194514600209 ◽

2014 ◽

Vol 25 ◽

pp. 1460020 ◽

Cited By ~ 4

Author(s):

ANDREA SIGNORI ◽

ALESSANDRO BACCHETTA ◽

MARCO RADICI

Keyword(s):

Transverse Momentum ◽

Pion Production ◽

Distribution Functions ◽

Momentum Dependence ◽

Parton Distribution Functions ◽

Final State ◽

Fragmentation Functions ◽

First Time ◽

Better Than ◽

Independent Model

Recent data from semi-inclusive deep inelastic scattering collected by the HERMES collaboration allow for the first time to discuss how the transverse-momentum dependence of unpolarized distribution and fragmentation functions is affected by the flavor of the involved partons. A model built with flavor-dependent Gaussian transverse-momentum distributions fits data better than the same flavor-independent model. The current analysis is performed for totally unpolarized scattering of leptons off protons and deuterons, with detected pions in the final state. There are convincing indications of flavor dependence in the fragmentation functions, while for parton distribution functions the evidence is weaker.

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Chebyshev matrix product states with canonical orthogonalization for spectral functions of strongly correlated systems

10.33774/chemrxiv-2021-jwdb5 ◽

2021 ◽

Author(s):

Tong Jiang ◽

Jiajun Ren ◽

Zhigang Shuai

Keyword(s):

Excited States ◽

Strongly Correlated Systems ◽

Time Dependent ◽

Matrix Product ◽

Strongly Correlated ◽

Effective Hamiltonian ◽

Spectral Functions ◽

Correlated Systems ◽

Matrix Product States ◽

First Time

We propose a method to calculate the spectral functions of strongly correlated systems by Chebyshev expansion in the framework of matrix product states coupled with canonical orthogonalization (coCheMPS). The canonical orthogonalization can improve the accuracy and efficiency significantly because the orthogonalized Chebyshev vectors can provide an ideal basis for constructing the effective Hamiltonian in which the exact recurrence relation can be retained. In addition, not only the spectral function but also the excited states and eigen energies can be directly calculated, which is usually impossible for other MPS-based methods such as time-dependent formalism or correction vector. The remarkable accuracy and efficiency of coCheMPS over other methods are demonstrated by calculating the spectral functions of spin chain and ab initio hydrogen chain. We demonstrate for the first time that Chebyshev MPS can be used in quantum chemistry. We also caution the application for electron-phonon system with densed density of states.

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Competing Spin Liquid Phases in the S=$\frac{1}{2}$ Heisenberg Model on the Kagome Lattice

SciPost Physics ◽

10.21468/scipostphys.7.1.006 ◽

2019 ◽

Vol 7 (1) ◽

Cited By ~ 6

Author(s):

Shenghan Jiang ◽

Panjin Kim ◽

Jung Hoon Han ◽

Ying Ran

Keyword(s):

Liquid Phase ◽

Ground State ◽

Simulation Method ◽

Model Systems ◽

Spin Liquid ◽

Topological Order ◽

Strongly Correlated ◽

Liquid Phases ◽

Different Types ◽

Spatial Dimensions

The properties of ground state of spin-\frac{1}{2}12 kagome antiferromagnetic Heisenberg (KAFH) model have attracted considerable interest in the past few decades, and recent numerical simulations reported a spin liquid phase. The nature of the spin liquid phase remains unclear. For instance, the interplay between symmetries and Z_2Z2 topological order leads to different types of Z_2Z2 spin liquid phases. In this paper, we develop a numerical simulation method based on symmetric projected entangled-pair states (PEPS), which is generally applicable to strongly correlated model systems in two spatial dimensions. We then apply this method to study the nature of the ground state of the KAFH model. Our results are consistent with that the ground state is a U(1)U(1) Dirac spin liquid rather than a Z_2Z2 spin liquid.

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