369 research outputs found
Results from 3D Electroweak Phase Transition Simulations
We study the phase transition in SU(2)-Higgs model on the lattice using the
3D dimensionally reduced formalism. The 3D formalism enables us to obtain
highly accurate Monte Carlo results, which we extrapolate both to the infinite
volume and to the continuum limit. Our formalism also provides for a
well-determined and unique way to relate the results to the perturbation
theory. We measure the critical temperature, latent heat and interface tension
for Higgs masses up to 70 GeV.Comment: 4 pages uuencoded postscript, contribution to LATTICE 9
Brane world scenario in the presence of a non-minimally coupled bulk scalar field
We present our recent work on brane world models with a non-minimally coupled
scalar field. In [9] we examined the stability of these models against scalar
field perturbations and we discussed possible physical implications, while in
[10] we developed a numerical approach for the solution of the Einstein
equations with the non-minimally coupled scalar field.Comment: 8 pages,1 figure, talk given in Nafplio NEB XII 200
Second Randall-Sundrum brane world scenario with a nonminimally coupled bulk scalar field
In our previous work of Ref. [5] we studied the stability of the RS2-model
with a nonminimally coupled bulk scalar field , and we found that in
appropriate regions of the standard RS2-vacuum becomes unstable. The
question that arises is whether there exist other new static stable solutions
where the system can relax. In this work, by solving numerically the Einstein
equations with the appropriate boundary conditions on the brane, we find that
depending on the value of the nonminimal coupling , this model possesses
three classes of new static solutions with different characteristics. We also
examine what happens when the fine tuning of the RS2-model is violated, and we
obtain that these three classes of solutions are preserved in appropriate
regions of the parameter space of the problem. The stability properties and
possible physical implications of these new solutions are discussed in the main
part of this paper. Especially in the case where ( is the
five dimensional conformal coupling) and the fine tuning is violated, we obtain
a physically interesting static stable solution.Comment: 22 pages, 13 figure
Effective Action for the Scalar Field Theory with Higher Vertices
We derive a new kind of recursion relation to obtain the
one-particle-irreducible (1PI) Feynman diagrams for the effective action. By
using this method, we have obtained the graphical representation of the
four-loop effective action in case of the general bosonic field theory which
have vertices higher than the four-point vertex
The Abelian Higgs Model in Three Dimensions with Improved Action
We study the Abelian Higgs Model using an improved form of the action in the
scalar sector. The subleading corrections are carefully analysed and the
connection between lattice and continuous parameters is worked out. The
simulation shows a remarkable improvement of the numerical performance.Comment: Minor correction to one-loop relations;reference adde
Multi--Layer Structure in the Strongly Coupled 5D Abelian Higgs Model
We explore the phase diagram of the five-dimensional anisotropic Abelian
Higgs model by Monte Carlo simulations. In particular, we study the transition
between the confining phase and the four dimensional layered Higgs phase. We
find that, in a certain region of the lattice parameter space, this transition
can be first order and that each layer moves into the Higgs phase independently
of the others (decoupling of layers). As the Higgs couplings vary, we find,
using mean field techniques, that this transition may probably become second
order.Comment: 16 page
3D Physics and the Electroweak Phase Transition: Perturbation Theory
We develop a method for the construction of the effective potential at high
temperatures based on the effective field theory approach and renormalization
group. It allows one to sum up the leading logarithms in all orders of
perturbation theory. The method reproduces the known one-loop and two-loop
results in a very simple and economic way and clarifies the issue of the
convergence of the perturbation theory. We also discuss the assumptions being
made for the determination of the critical temperature of the electroweak phase
transition, and analyse different perturbative uncertainties in its
determination. These results are then used for the non-perturbative lattice
Monte Carlo simulations of the EW phase transition in forthcoming paper.Comment: 44 pages, preprint CERN-TH.6973/9
Three-dimensional lattice U(1) gauge-Higgs model at low
We study the non-compact version of the U(1) gauge-Higgs model in three
dimensions for We found that, using this formulation, rather
modest lattices approach quite well the infinite volume behaviour.The phase
transition is first order, as expected for this Higgs mass. The latent heat (in
units of ) is compatible with the predictions of the two-loop
effective potential; it is an order of magnitude less than the corresponding
SU(2) value. The transition temperature and in units of
the critical temperature are also compatible with the perturbative results.Comment: 15 pages, latex, 9 figures, changes in the comparison with
perturbation theor
Non-Linear Sigma Model and asymptotic freedom at the Lifshitz point
We construct the general O(N)-symmetric non-linear sigma model in 2+1
spacetime dimensions at the Lifshitz point with dynamical critical exponent
z=2. For a particular choice of the free parameters, the model is
asymptotically free with the beta function coinciding to the one for the
conventional sigma model in 1+1 dimensions. In this case, the model admits also
a simple description in terms of adjoint currents.Comment: 23 pages, 2 figure
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