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Sep 21, 2013
09/13

by
A. Krasnitz; R. Potting

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We measure the diffusion rate of Chern-Simons number in the (1+1)-dimensional Abelian Higgs model interacting with a realistic heat bath for temperatures between 1/13 and 2/3 times the sphaleron energy. It is found that the measured rate is close to that predicted by the sphaleron approximation at the lower end of the temperature range considered but falls at least an order of magnitude short of the sphaleron estimate at the upper end of that range. We show numerically that the sphaleron...

Source: http://arxiv.org/abs/hep-lat/9312062v1

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Sep 18, 2013
09/13

by
P. H. Damgaard; U. M. Heller; A. Krasnitz; T. Madsen

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Three-dimensional lattice QCD is studied by Monte Carlo simulations within the quenched approximation. At zero temperature a quark-antiquark condensate is observed in the limit of vanishing quark masses. The condensate vanishes continuously at the finite-temperature deconfinement phase transition of the theory. A natural interpretation of this phenomenon in the full theory with dynamical quarks is in terms of the spontaneous flavor symmetry breaking $U(N_f) \to U(N_f/2)\times U(N_f/2)$. In...

Source: http://arxiv.org/abs/hep-lat/9803012v3

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Sep 21, 2013
09/13

by
Khalil M. Bitar; R. Edwards; Steven Gottlieb; U. M. Heller; A. D. Kennedy; J. B. Kogut; A. Krasnitz; W. Liu; Michael C. Ogilvie; R. L. Renken; D. K. Sinclair; R. L. Sugar; D. Toussaint; K. C. Wang

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We have extended our previous study of the lattice QCD spectrum with 2 flavors of staggered dynamical quarks at $6/g^2=5.6$ and $am_q=0.025$ and 0.01 to larger lattices, with better statistics and with additional sources for the propagators. The additional sources allowed us to estimate the $\Delta$ mass and to measure the masses of all mesons whose operators are local in time. These mesons show good evidence for flavor symmetry restoration, except for the masses of the Goldstone and...

Source: http://arxiv.org/abs/hep-lat/9311027v1

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36

Sep 20, 2013
09/13

by
A. Krasnitz; R. Potting

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We propose a new method of studying a real-time canonical evolution of field-theoretic systems with boundary coupling to a realistic heat bath. In the free-field case the method is equivalent to an infinite extension of the system beyond the boundary, while in the interacting case the extension of the system is done in linear approximation. We use this technique to study kink-antikink dynamics in $\varphi^4$ field theory in 1+1 dimensions.

Source: http://arxiv.org/abs/hep-lat/9212033v1

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30

Sep 21, 2013
09/13

by
A. Kovner; A. Krasnitz; R. Potting

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We investigate the effect of dynamical fermions on the sphaleron transition rate at finite temperature for the Abelian Higgs model in one spatial dimension. The fermion degrees of freedom are included through bosonization. Using a numerical simulation, we find that massless fermions do not change the rate within the measurement accuracy. Surprisingly, the exponential dependence of the sphaleron energy on the Yukawa coupling is not borne out by the transition rate, which shows a very weak...

Source: http://arxiv.org/abs/hep-ph/9907381v1

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36

Sep 20, 2013
09/13

by
A. Krasnitz; R. Potting

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We measure the diffusion rate of Chern-Simons number in the (1+1)-dimensional Abelian Higgs model interacting with a realistic heat bath for temperatures between 1/13 and 1/3 times the sphaleron energy. It is found that the measured rate is close to that predicted by one-loop calculation at the lower end of the temperature range considered but falls at least an orderof magnitude short of one-loop estimate at the upper end of that range. We show numerically that the sphaleron approximation...

Source: http://arxiv.org/abs/hep-ph/9308307v2

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Jul 20, 2013
07/13

by
Ph. de Forcrand; A. Krasnitz; R. Potting

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We study the Chern-Simons number diffusion rate in the (1+1)-dimensional latticeAbelian Higgs model at temperatures much higher than, as well as comparable to, the sphaleron energy. It is found that in the high-temperature limit the rate is likely to grow as power 2/3 of the temperature. In the intermediate-temperature regime, our numerical simulations show that very weak temperature dependence of the rate, found in previous work, persists at smaller lattice spacings. We discuss possibilities...

Source: http://arxiv.org/abs/hep-ph/9407241v1

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Sep 18, 2013
09/13

by
J. Ambjorn; K. N. Anagnostopoulos; A. Krasnitz

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We discuss recent results obtained from simulations of high temperature, classical, real time dynamics of SU(2) Yang-Mills theory at temperatures of the order of the electroweak scale. Measurements of gauge covariant and gauge invariant autocorrelations of the fields indicate that the ASY-Bodecker scenario is irrelevant at these temperatures.

Source: http://arxiv.org/abs/hep-lat/0110092v1

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Sep 23, 2013
09/13

by
C. Bernard; T. A. DeGrand; C. DeTar; S. Gottlieb; A. Krasnitz; R. L. Sugar; D. Toussaint

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As part of an ongoing effort to characterize the high temperature phase of QCD, we measure the quark baryon density in the vicinity of a fixed test quark and compare it with similar measurements at low temperature and at the crossover temperature. Such an observable has also been studied by the Vienna group. We find an extremely weak correlation at high temperature, suggesting that small color singlet clusters are unimportant in the thermal ensemble. We also find that at T = 0.75 T_c the...

Source: http://arxiv.org/abs/hep-lat/9211036v1

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Sep 19, 2013
09/13

by
K. M. Bitar; T. DeGrand; R. Edwards; S. Gottlieb; U. M. Heller; A. D. Kennedy; J. B. Kogut; A. Krasnitz; W. Liu; M. C. Ogilvie; R. L. Renken; P. Rossi; D. K. Sinclair; R. L. Sugar; D. Toussaint; K. C. Wang

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We have measured some simple matrix elements for pseudoscalar and vector mesons made of Wilson valence quarks and staggered sea quarks at $\beta=5.6$ at sea quark masses $am_q=0.01$ and 0.025. Our measurements include the decay constants of pseudoscalars (including $f_D$), the wave function at the origin (or decay constant) of vector mesons, and the calculation of quark masses from current algebra. The effects of sea quarks on the simulations are small. We make comparisons to quenched...

Source: http://arxiv.org/abs/hep-lat/9301018v1

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Sep 19, 2013
09/13

by
A. Krasnitz; R. Venugopalan

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We report results of our ongoing nonperturbative numerical study of a classical effective theory describing low-x partons in the central region of a heavy-ion collision. In particular, we give estimates of the initial transverse energies and multiplicities for a wide range of collision regimes, including those at RHIC and at LHC.

Source: http://arxiv.org/abs/hep-ph/0102118v1

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Sep 21, 2013
09/13

by
C. Bernard; T. Blum; T. DeGrand; C. Detar; S. Gottlieb; A. Krasnitz; R. Sugar; D. Toussaint

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We have carried out spectrum calculations with two flavors of dynamical Kogut-Susskind quarks on four lattice sizes from $8^3\times 24$ to $16^3\times24$ at couplings that correspond to chiral symmetry restoration for a lattice with 6 time slices. We estimate that the linear spatial sizes of the lattices range from 1.8 to 3.6 fm. We find significant finite size effects for all particles between the smallest and largest volume with the larger quark mass that we study, $am_q=0.025$, where $a$ is...

Source: http://arxiv.org/abs/hep-lat/9305023v1

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Sep 21, 2013
09/13

by
J. Ambjørn; A. Krasnitz

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Results of a large scale numerical simulation show that the high temperature Chern-Simons number diffusion rate in the electroweak theory has a classical limit $\Gamma = \kappa (\alpha_w T)^4$, where $\kappa = 1.09\pm 0.04$ and $\alpha_w$ is the weak fine structure constant.

Source: http://arxiv.org/abs/hep-ph/9508202v2

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Sep 20, 2013
09/13

by
A. Krasnitz

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I propose a method, based on a set of Langevin equations, for bringing classical gauge theories to thermal equilibrium while respecting the set of Gauss' constraints exactly. The algorithm is described in detail for the SU(2) gauge theory with or without the Higgs doublet. As an example of application, canonical average of the maximal Lyapunov exponent is computed for the SU(2) Yang-Mills theory.

Source: http://arxiv.org/abs/hep-lat/9507025v1

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42

Sep 21, 2013
09/13

by
J. Ambjorn; A. Krasnitz

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We determine the sphaleron transition rate using real time lattice simulations of the classical system. An improved definition of the lattice topological charge allows us to obtain a more reliable estimate of the transition rate. For an SU(2) Yang-Mills-Higgs system in the broken phase we find the transition rate to be strongly suppressed, and we have observed no sphaleron transitions in the range of coupling constants used. For a pure SU(2) Yang-Mills system in large volumes the rate behaves...

Source: http://arxiv.org/abs/hep-ph/9705380v1

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31

Sep 20, 2013
09/13

by
P. H. Damgaard; U. M. Heller; A. Krasnitz

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Measurements of the lowest-lying eigenvalues of the staggered fermion Dirac operator are made on ensembles of equilibrium gauge field configurations in quenched SU(3) lattice gauge theory. The results are compared with exact analytical predictions in the microscopic finite-volume scaling regime.

Source: http://arxiv.org/abs/hep-lat/9810060v1

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Sep 23, 2013
09/13

by
K. M. Bitar; R. Edwards; T. A. DeGrand; Steven Gottlieb; U. M. Heller; A. D. Kennedy; J. B. Kogut; A. Krasnitz; W. Liu; M. C. Ogilvie; R. L. Renken; D. K. Sinclair; R. L. Sugar; D. Toussaint; K. C. Wang

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We present preliminary results from the 1991 HEMCGC simulations with staggered dynamical fermions on a $16^3 \times 32$ lattice at $\beta = 5.6$ with sea quark masses $am_q = 0.025$ and 0.01. The spectroscopy was done both for staggered valence quarks with mass equal to the sea quark masses and for Wilson valence quarks at six different values for $\kappa$, 0.1320, 0.1410, 0.1525, 0.1565, 0.1585, and 0.1600. In addition to the measurements performed in our earlier work, we also measured the...

Source: http://arxiv.org/abs/hep-lat/9201005v1

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37

Sep 23, 2013
09/13

by
D. Kharzeev; A. Krasnitz; R. Venugopalan

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We compute numerically the topological charge distribution in the initial stage of a high energy heavy ion collision. This charge distribution is generated by Chern-Simons number fluctuations associated with the dynamics of strong classical fields in the initial state. The distribution is found to be quite narrow at RHIC and LHC energies reflecting a small value of the topological susceptibility. Thus the effective potential of classical fields is shallow in the $\theta$-direction likely...

Source: http://arxiv.org/abs/hep-ph/0109253v1

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50

Sep 21, 2013
09/13

by
K. M. Bitar; T. A. DeGrand; R. G. Edwards; S. Gottlieb; U. M. Heller; A. D. Kennedy; J. B. Kogut; A. Krasnitz; W. Liu; M. C. Ogilvie; R. L. Renken; P. Rossi; D. K. Sinclair; R. L. Sugar; D. Toussaint; K. C. Wang

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We present an analysis of hadronic spectroscopy for Wilson valence quarks with dynamical staggered fermions at lattice coupling $6/g^2 = \beta=5.6$ at sea quark mass $am_q=0.01$ and 0.025, and of Wilson valence quarks in quenched approximation at $\beta=5.85$ and 5.95, both on $16^3 \times 32$ lattices. We make comparisons with our previous results with dynamical staggered fermions at the same parameter values but on $16^4$ lattices doubled in the temporal direction.

Source: http://arxiv.org/abs/hep-lat/9204008v1

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Sep 23, 2013
09/13

by
The MILC Collaboration; C. Bernard; T. A. DeGrand; C. DeTar; Steven Gottlieb; A. Krasnitz; R. Authors; :; L. Sugar; D. Toussaint

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We have continued our study of finite size effects in the QCD spectrum on lattices ranging in size from $8^3\times 24$ to $16^3\times24$. We have increased our statistics for quark mass $am_q=0.025$ for the smallest lattice size. In addition, we have studied quark mass 0.0125 for lattice sizes $12^3\times24$ and $16^3\times24$. These lattice sizes correspond to a box 1.8--3.6 fm on a side when the rho mass at zero quark mass is used to set the scale. We discuss the nucleon to rho mass ratio at...

Source: http://arxiv.org/abs/hep-lat/9211007v1

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48

Sep 18, 2013
09/13

by
J. Ambjorn; K. N. Anagnostopoulos; A. Krasnitz

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We test at the electroweak scale the recently proposed elaborate theoretical scenario for real-time dynamics of non-abelian gauge theories at high temperature. We see no sign of the predicted behavior. This indicates that perturbative concepts like color conductivity and Landau damping might be irrelevant at temperatures corresponding to the electroweak scale.

Source: http://arxiv.org/abs/hep-ph/0101309v1