293 research outputs found
Screening and Deconfinement of Sources in Finite Temperature SU(2) Lattice Gauge Theory
Deconfinement and screening of higher-representation sources in
finite-temperature lattice gauge theory is investigated by both
analytical and numerical means. The effective Polyakov-line action at strong
coupling is simulated by an efficient cluster-updating Monte Carlo algorithm
for the case of dimensions. The results compare very favourably with
an improved mean-field solution. The limit of the
theory is shown to be highly singular as far as critical behaviour is
concerned. In that limit the leading amplitudes of higher representation
Polyakov lines vanish at strong coupling, and subleading exponents become
dominant. Each of the higher-representation sources then effectively carry with
them their own critical exponents.Comment: 13pages+7figures, CERN-TH-7222/94 One reference added, else unchange
Alternative Solution of Strong CP
In this talk I begin with some general discussion of the history of CP
violation, then move on to aspects of a spontaneous CP violation model
including the production of new particles at LHC, implications for B decay,
generalized Cabibbo mixing and a reevaluation of kaon CP violation. Finally
there is a summary.Comment: 4 pages Latex. Talk at Fifth IFT Workshop: Axions. March 199
Global effects of local sound-speed perturbations in the Sun: A theoretical study
We study the effect of localized sound-speed perturbations on global mode
frequencies by applying techniques of global helioseismology on numerical
simulations of the solar acoustic wave field. Extending the method of
realization noise subtraction (e.g. Hanasoge et al. 2007) to global modes and
exploiting the luxury of full spherical coverage, we are able to achieve very
highly resolved frequency differences that are used to study sensitivities and
the signatures of the thermal asphericities. We find that (1) global modes are
almost twice as sensitive to sound-speed perturbations at the bottom of the
convection zone as in comparison to anomalies well in the radiative interior
(), (2) the -degeneracy is lifted ever so slightly,
as seen in the coefficients, and (3) modes that propagate in the vicinity
of the perturbations show small amplitude shifts ().Comment: Submitted to Solar Physic
Polyakov Loops versus Hadronic States
The order parameter for the pure Yang-Mills phase transition is the Polyakov
loop which encodes the symmetries of the Z_N center of the SU(N) gauge group.
On the other side the physical degrees of freedom of any asymptotically free
gauge theory are hadronic states. Using the Yang-Mills trace anomaly and the
exact Z_N symmetry we construct a model able to communicate to the hadrons the
information carried by the order parameter.Comment: RevTex4 2-col., 6 pages, 2 figures. Typos fixed and added a paragraph
in the conclusion
Meridional Circulation and Global Solar Oscillations
We investigate the influence of large-scale meridional circulation on solar
p-modes by quasi-degenerate perturbation theory, as proposed by
\cite{lavely92}. As an input flow we use various models of stationary
meridional circulation obeying the continuity equation. This flow perturbs the
eigenmodes of an equilibrium model of the Sun. We derive the signatures of the
meridional circulation in the frequency multiplets of solar p-modes. In most
cases the meridional circulation leads to negative average frequency shifts of
the multiplets. Further possible observable effects are briefly discussed.Comment: 14 pages, 5 figures, submittted to Solar Physics Topical Issue
"HELAS
Punctuated equilibria and 1/f noise in a biological coevolution model with individual-based dynamics
We present a study by linear stability analysis and large-scale Monte Carlo
simulations of a simple model of biological coevolution. Selection is provided
through a reproduction probability that contains quenched, random interspecies
interactions, while genetic variation is provided through a low mutation rate.
Both selection and mutation act on individual organisms. Consistent with some
current theories of macroevolutionary dynamics, the model displays
intermittent, statistically self-similar behavior with punctuated equilibria.
The probability density for the lifetimes of ecological communities is well
approximated by a power law with exponent near -2, and the corresponding power
spectral densities show 1/f noise (flicker noise) over several decades. The
long-lived communities (quasi-steady states) consist of a relatively small
number of mutualistically interacting species, and they are surrounded by a
``protection zone'' of closely related genotypes that have a very low
probability of invading the resident community. The extent of the protection
zone affects the stability of the community in a way analogous to the height of
the free-energy barrier surrounding a metastable state in a physical system.
Measures of biological diversity are on average stationary with no discernible
trends, even over our very long simulation runs of approximately 3.4x10^7
generations.Comment: 20 pages RevTex. Minor revisions consistent with published versio
Constructing and Characterising Solar Structure Models for Computational Helioseismology
In this paper, we construct background solar models that are stable against
convection, by modifying the vertical pressure gradient of Model S
(Christensen-Dalsgaard et al., 1996, Science, 272, 1286) relinquishing
hydrostatic equilibrium. However, the stabilisation affects the eigenmodes that
we wish to remain as close to Model S as possible. In a bid to recover the
Model S eigenmodes, we choose to make additional corrections to the sound speed
of Model S before stabilisation. No stabilised model can be perfectly
solar-like, so we present three stabilised models with slightly different
eigenmodes. The models are appropriate to study the f and p1 to p4 modes with
spherical harmonic degrees in the range from 400 to 900. Background model CSM
has a modified pressure gradient for stabilisation and has eigenfrequencies
within 2% of Model S. Model CSM_A has an additional 10% increase in sound speed
in the top 1 Mm resulting in eigenfrequencies within 2% of Model S and
eigenfunctions that are, in comparison with CSM, closest to those of Model S.
Model CSM_B has a 3% decrease in sound speed in the top 5 Mm resulting in
eigenfrequencies within 1% of Model S and eigenfunctions that are only
marginally adversely affected. These models are useful to study the interaction
of solar waves with embedded three-dimensional heterogeneities, such as
convective flows and model sunspots. We have also calculated the response of
the stabilised models to excitation by random near-surface sources, using
simulations of the propagation of linear waves. We find that the simulated
power spectra of wave motion are in good agreement with an observed SOHO/MDI
power spectrum. Overall, our convectively stabilised background models provide
a good basis for quantitative numerical local helioseismology. The models are
available for download from http://www.mps.mpg.de/projects/seismo/NA4/.Comment: 35 pages, 23 figures Changed title Updated Figure 1
Partial Deconfinement in Color Superconductivity
We analyze the fate of the unbroken SU(2) color gauge interactions for 2
light flavors color superconductivity at non zero temperature. Using a simple
model we compute the deconfining/confining critical temperature and show that
is smaller than the critical temperature for the onset of the superconductive
state itself. The breaking of Lorentz invariance, induced already at zero
temperature by the quark chemical potential, is shown to heavily affect the
value of the critical temperature and all of the relevant features related to
the deconfining transition. Modifying the Polyakov loop model to describe the
SU(2) immersed in the diquark medium we argue that the deconfinement transition
is second order. Having constructed part of the equation of state for the 2
color superconducting phase at low temperatures our results are relevant for
the physics of compact objects featuring a two flavor color superconductive
state.Comment: 9 pp, 4 eps-figs, version to appear in PR
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