3,728 research outputs found

### 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

### 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

### Three-dimensional lattice U(1) gauge-Higgs model at low $m_H$

We study the non-compact version of the U(1) gauge-Higgs model in three
dimensions for $m_H = 30 GeV.$ 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 $T_{cr}^4$) 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

### Curvatons in the minimally supersymmetric standard model

Curvaton is an effectively massless field whose energy density during
inflation is negligible but which later becomes dominant. This is a novel
mechanism to generate the scale invariant perturbations. I discuss the
possibility that the curvaton could be found among the fields of the minimally
supersymmetric standard model (MSSM), which contains a number of flat
directions along which the renormalizable potential vanishes. The requirements
of late domination and the absence of damping of the perturbations pick out
essentially a unique candidate for the MSSM curvaton. One must also require
that inflation takes place in a hidden sector. If the inflaton energy density
can be radiated into extra dimensions, many constraints can be relaxed, and the
simplest flat direction consisting of the Higgses H_u and H_d would provide a
working example of an MSSM curvaton.Comment: 16 pages, 1 Figur

### Curvaton Scenario with Affleck-Dine Baryogenesis

We discuss the curvaton scenario with the Affleck-Dine baryogenesis. In this
scenario, non-vanishing baryonic entropy fluctuation may be generated even
without primordial fluctuation of the Affleck-Dine field. Too large entropy
fluctuation is inconsistent with the observations and hence constraints on the
curvaton scenario with the Affleck-Dine baryogenesis are obtained. We calculate
the baryonic entropy fluctuation (as well as other cosmological density
fluctuations) in this case and derive constraints. Implications to some of the
models of the curvaton are also discussed.Comment: 16 pages,2 figure

### A-term inflation and the MSSM

The parameter space for A-term inflation is explored with $W=\lambda_p
\phi^p/(p M_P^{p-3})$. With p=6 and \lambda_p~1, the observed spectrum and
spectral tilt can be obtained with soft mass of order 10^2 GeV but not with a
much higher mass. The case p=3 requires \lambda_p~10^{-9} to 10^{-12}. The
ratio m/A requires fine-tuning, which may be justified on environmental
grounds. An extension of the MSSM to include non-renormalizable terms and/or
Dirac neutrino masses might support either A-term inflation or modular
inflation.Comment: 10 pages, 3 figures; Comments added, typos correcte

### Layered Higgs Phase as a Possible Field Localisation on a Brane

So far it has been found by using lattice techniques that in the anisotropic
five--dimensional Abelian Higgs model, a layered Higgs phase exists in addition
to the expected five--dimensional one. The exploration of the phase diagram has
shown that the two Higgs phases are separated by a phase transition from the
confining phase. This transition is known to be first order. In this paper we
explore the possibility of finding a second order transition point in the
critical line which separates the first order phase transition from the
crossover region. This is shown to be the case only for the four--dimensional
Higgs layered phase whilst the phase transition to the five--dimensional broken
phase remains first order. The layered phase serves as the possible realisation
of four--dimensional spacetime dynamics which is embedded in a
five--dimensional spacetime. These results are due to gauge and scalar field
localisation by confining interactions along the extra fifth direction.Comment: 1+15 pages, 12 figure

### Gravity-induced instability and gauge field localization

The spectrum of a massless bulk scalar field \Phi, with a possible
interaction term of the form -\xi R \Phi^{2}, is investigated in the case of
RS-geometry [1]. We show that the zero mode for \xi=0, turns into a tachyon
mode, in the case of a nonzero negative value of \xi (\xi<0). As we see, the
existence of the tachyon mode destabilizes the \Phi=0 vacuum, against a new
stable vacuum with nonzero \Phi near the brane, and zero in the bulk. By using
this result, we can construct a simple model for the gauge field localization,
according to the philosophy of Dvali and Shifman (Higgs phase on the brane,
confinement in the bulk).Comment: 12 pages,4 figures, minor corrections, references adde

### MSSM Higgses as the source of reheating and all matter

We consider the possibility that the dark energy responsible for inflation is
deposited into extra dimensions outside of our observable universe. Reheating
and all matter can then be obtained from the MSSM flat direction condensate
involving the Higgses $H_u$ and $H_d$, which acquires large amplitude by virtue
of quantum fluctuations during inflation. The reheat temperature is $T_{RH}
\lesssim 10^9$ GeV so that there is no gravitino problem. We find a spectral
index $n_s\approx 1$ with a very weak dependence on the Higgs potential.Comment: 4 page

### O(a^2) cutoff effects in lattice Wilson fermion simulations

In this paper we propose to interpret the large discretization artifacts
affecting the neutral pion mass in maximally twisted lattice QCD simulations as
O(a^2) effects whose magnitude is roughly proportional to the modulus square of
the (continuum) matrix element of the pseudoscalar density operator between
vacuum and one-pion state. The numerical size of this quantity is determined by
the dynamical mechanism of spontaneous chiral symmetry breaking and turns out
to be substantially larger than its natural magnitude set by the value of
Lambda_QCD.Comment: 38 pages, 1 figure, 2 table

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