4,947 research outputs found
New Phases of SU(3) and SU(4) at Finite Temperature
The addition of an adjoint Polyakov loop term to the action of a pure gauge
theory at finite temperature leads to new phases of SU(N) gauge theories. For
SU(3), a new phase is found which breaks Z(3) symmetry in a novel way; for
SU(4), the new phase exhibits spontaneous symmetry breaking of Z(4) to Z(2),
representing a partially confined phase in which quarks are confined, but
diquarks are not. The overall phase structure and thermodynamics is consistent
with a theoretical model of the effective potential for the Polyakov loop based
on perturbation theory.Comment: 18 pages, 17 figures, RevTeX
Probabilistic abstract interpretation: From trace semantics to DTMC’s and linear regression
In order to perform probabilistic program analysis we need to consider probabilistic languages or languages with a probabilistic semantics, as well as a corresponding framework for the analysis which is able to accommodate probabilistic properties and properties of probabilistic computations. To this purpose we investigate the relationship between three different types of probabilistic semantics for a core imperative language, namely Kozen’s Fixpoint Semantics, our Linear Operator Semantics and probabilistic versions of Maximal Trace Semantics. We also discuss the relationship between Probabilistic Abstract Interpretation (PAI) and statistical or linear regression analysis. While classical Abstract Interpretation, based on Galois connection, allows only for worst-case analyses, the use of the Moore-Penrose pseudo inverse in PAI opens the possibility of exploiting statistical and noisy observations in order to analyse and identify various system properties
A computational group theoretic symmetry reduction package for the SPIN model checker
Symmetry reduced model checking is hindered by two problems: how to identify state space symmetry when systems are not fully symmetric, and how to determine equivalence of states during search. We present TopSpin, a fully automatic symmetry reduction package for the Spin model checker. TopSpin uses the Gap computational algebra system to effectively detect state space symmetry from the associated Promela specification, and to choose an efficient symmetry reduction strategy by classifying automorphism groups as a disjoint/wreath product of subgroups. We present encouraging experimental results for a variety of Promela examples
The second moment of the pion's distribution amplitude
We present preliminary results for the second moment of the pion's
distribution amplitude. The lattice formulation and the phenomenological
implications are briefly reviewed, with special emphasis on some subtleties
that arise when the Lorentz group is replaced by the hypercubic group. Having
analysed more than half of the available configurations, the result obtained is
\xi^2_L = 0.06 \pm 0.02.Comment: Lattice 99 (matrix elements), 3 page
Oncogenic K-Ras suppresses IP<sub>3</sub>-dependent Ca<sup>2+</sup> release through remodeling of IP<sub>3</sub>Rs isoform composition and ER luminal Ca<sup>2+</sup> levels in colorectal cancer cell lines
The GTPase Ras is a molecular switch engaged downstream of G-protein coupled receptors and receptor tyrosine inases that controls multiple cell fate-determining signalling athways. Ras signalling is frequently deregulated in cancer underlying associated changes in cell phenotype. Although Ca2+ signalling pathways control some overlapping functions with Ras, and altered Ca2+ signalling pathways are emerging as important players in oncogenic transformation, how Ca2+ signalling is remodelled during transformation and whether it has a causal role remains unclear. We have investigated Ca2+ signalling in two human colorectal cancer cell lines and their isogenic derivatives in which the mutated K-Ras allele (G13D) has been deleted by homologous recombination. We show that agonist-induced Ca2+ release from intracellular stores is enhanced by loss of K-RasG13D through an increase in the ER store content and a modification of IP3R subtype abundance. Consistently, uptake of Ca2+ into mitochondria and sensitivity to apoptosis was enhanced as a result of KRasG13D loss. These results suggest that suppression of Ca2+ signalling is a common response to naturally occurring levels of K-RasG13D that contributes to a survival
advantage during oncogenic transformation
Light hadrons with improved staggered quarks: approaching the continuum limit
We have extended our program of QCD simulations with an improved
Kogut-Susskind quark action to a smaller lattice spacing, approximately 0.09
fm. Also, the simulations with a approximately 0.12 fm have been extended to
smaller quark masses. In this paper we describe the new simulations and
computations of the static quark potential and light hadron spectrum. These
results give information about the remaining dependences on the lattice
spacing. We examine the dependence of computed quantities on the spatial size
of the lattice, on the numerical precision in the computations, and on the step
size used in the numerical integrations. We examine the effects of
autocorrelations in "simulation time" on the potential and spectrum. We see
effects of decays, or coupling to two-meson states, in the 0++, 1+, and 0-
meson propagators, and we make a preliminary mass computation for a radially
excited 0- meson.Comment: 43 pages, 16 figure
An Algorithmic Approach to Quantum Field Theory
The lattice formulation provides a way to regularize, define and compute the
Path Integral in a Quantum Field Theory. In this paper we review the
theoretical foundations and the most basic algorithms required to implement a
typical lattice computation, including the Metropolis, the Gibbs sampling, the
Minimal Residual, and the Stabilized Biconjugate inverters. The main emphasis
is on gauge theories with fermions such as QCD. We also provide examples of
typical results from lattice QCD computations for quantities of
phenomenological interest.Comment: 44 pages, to be published in IJMP
How the mere desire for certainty can lead to a preference for men in authority (particularly among political liberals)
Women are harmed by stereotypes about their fit for positions of authority and changing these stereotypes is not a simple task. As stereotypes have strong epistemic properties, individuals with a high need for cognitive closure (NCC; i.e., the desire for epistemic certainty) can be more likely to accept these stereotypes and, consequently, to prefer men in positions of authority. Consistent with the reactive liberal hypothesis, this effect could be actually more visible among individuals with both a high NCC and left-wing political orientations. We supported these hypotheses in a series of three studies. In Study 1 (N = 217), we found that manipulated NCC predicted preference for men in authority through stereotypes of women as not being fit for authority in a measurement-of-mediation design. In Study 2 (N = 151), we supported this effect in a mediation-as-process design. In Study 3 (N = 391), we found the indirect NCC effect on preference for men in authority was more visible among political liberals. A major implication of this work is that ways of changing the effect of these stereotypes should take into account the NCC, but particularly among individuals with left-wing beliefs
Towards a lattice determination of the coupling
The coupling is related to the form factor at zero
momentum of the axial current between - and -states. This form
factor is evaluated on the lattice using static heavy quarks and light quark
propagators determined by a stochastic inversion of the fermionic bilinear. The
\gBBP coupling is related to the coupling between heavy mesons and
low-momentum pions in the effective heavy meson chiral lagrangian. The coupling
of the effective theory can therefore be computed by numerical simulations. We
find the value . Besides its theoretical interest, the
phenomenological implications of such a determination are discussed.Comment: 20 pages, 6 figure
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