133 research outputs found
Kallen-Lehman approach to 3D Ising model
A "Kallen-Lehman" approach to Ising model, inspired by quantum field theory a
la Regge, is proposed. The analogy with the Kallen-Lehman representation leads
to a formula for the free-energy of the 3D model with few free parameters which
could be matched with the numerical data. The possible application of this
scheme to the spin glass case is shortly discussed.Comment: 13 pages no figures. Accepted for pubblication on Physics Letters
Constraining Monopoles by Topology: an Autonomous System
We find both analytical and numerical solutions of SU(2) Yang-Mills with an
adjoint Higgs field within both closed and open tubes whose sections are
spherical caps. This geometry admits a smooth limit in which the space-like
metric is flat and, moreover, allows one to use analytical tools which in the
flat case are not available. Some of the analytic configurations, in the limit
of vanishing Higgs coupling, correspond to magnetic monopoles and dyons living
within this tube-shaped domain. However, unlike what happens in the standard
case, analytical solutions can also be found in the case in which the Higgs
coupling is non-vanishing. We further show that the system admits long-lived
breathers.Comment: 20 pages, 9 figures, minor corrections, version accepted in JHE
Back Reaction from Trace Anomaly in RN-blackholes Evaporation
A model is proposed to describe a transition from a charged black hole of
mass and charge to one of mass and charge . The
basic equations are derived from the non-vacuum Einstein field equations
sourced by the Coulomb field and by a null scalar field with a nonvanishing
trace anomaly. It is shown that the nonvanishing trace of the energy-momentum
tensor prevents the formation of a naked singularity.Comment: 16 pages Late
Casimir energy in the Gribov-Zwanziger approach to QCD
In this paper we study the Casimir energy of QCD within the Gribov-Zwanziger
approach. In this model non-perturbative effects of gauge copies are properly
taken into account. We show that the computation of the Casimir energy for the
MIT bag model within the (refined) Gribov-Zwanziger approach not only gives the
correct sign but it also gives an estimate for the radius of the bag.Comment: 5 pages, No figures. The discussion about the constraints on the RGZ
parameters (as well as about the corresponding estimates) imposed by the
requirement to have the correct behaviour of the Casimir energy has been
expanded. Version accepted for publication on Physical Review
Cosmological consequences of an inhomogeneous space-time
Astrophysical observations provide a picture of the universe as a 4-dim homogeneous and isotropic flat space-time dominated by an unknown form of dark energy. To achieve such a cosmology one has to consider in the early universe an inflationary era able to overcome problems of standard cosmological models. Here an inhomogeneous model is proposed which allows to obtain a Friedmann-Robertson-Walker behaviour far away from the inhomogeneities and it naturally describes structures formation. We also obtain that the cosmological term does not prevent structure formation, avoiding a fine tuning problem in initial conditions. The asymptotic exact solution have been calculated. A simple test with universe age prediction has been performed. A relation between the inhomogeneity, the breaking of time reversal, parity and the matter-antimatter asymmetry is briefly discussed
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