422 research outputs found
Effective potential and vacuum stability
By following previous work on this subject, we investigate the issue of the
instability of the electroweak vacuum against the top loop corrections by
performing an accurate analysis of a Higgs-Yukawa model. We find that, when the
physical cutoff is properly implemented in the theory, the potential does not
exhibit any instability. Moreover, contrary to recent claims, we show that this
instability cannot be understood in terms of the very insightful work of Wu and
Weinberg on the non-convexity of the one-loop effective potential of a scalar
theory. Some of the theoretical and phenomenological consequences of our
results are briefly discussed.Comment: 10 pages, 4 figure
Top Radiative Corrections in Non-minimal Standard Models
We derive the one-loop effective action induced by a heavy top in models with
an extended Higgs sector. We use the effective action to analyze the top
corrections to the parameter and to the Higgs-gauge boson couplings. We
show that in models with at tree-level, one does not lose
generally the bound on from the parameter.Comment: 9 pages, phyzzx file, UPR-0603T. (a new reference has been added
Phase Structure of d=2+1 Compact Lattice Gauge Theories and the Transition from Mott Insulator to Fractionalized Insulator
Large-scale Monte Carlo simulations are employed to study phase transitions
in the three-dimensional compact abelian Higgs model in adjoint representations
of the matter field, labelled by an integer q, for q=2,3,4,5. We also study
various limiting cases of the model, such as the lattice gauge theory,
dual to the spin model, and the 3DXY spin model which is dual to the
lattice gauge theory in the limit . We have computed the
first, second, and third moments of the action to locate the phase transition
of the model in the parameter space , where is the
coupling constant of the matter term, and is the coupling constant of
the gauge term. We have found that for q=3, the three-dimensional compact
abelian Higgs model has a phase-transition line which
is first order for below a finite {\it tricritical} value
, and second order above. We have found that the
first order phase transition persists for finite and
joins the second order phase transition at a tricritical point
. For
all other integer we have considered, the entire phase transition
line is critical.Comment: 17 pages, 12 figures (new Fig. 2), new Section IVB, updated
references, submitted to Physical Review
Self-consistent radiative corrections to false vacuum decay
With the Higgs mass now measured at the sub-percent level, the potential metastability of the electroweak vacuum of the Standard Model (SM) motivates renewed study of false vacuum decay in quantum field theory. In this note, we describe an approach to calculating quantum corrections to the decay rate of false vacua that is able to account fully and self-consistently for the underlying inhomogeneity of the solitonic tunneling configuration. We show that this method can be applied both to theories in which the instability arises already at the level of the classical potential and those in which the instability arises entirely through radiative effects, as is the case for the SM Higgs vacuum. We analyse two simple models in the thin-wall regime, and we show that the modifications of the one-loop corrections from accounting fully for the inhomogeneity can compete at the same level as the two-loop homogeneous corrections
Electric charge quantization and the muon anomalous magnetic moment
We investigate some proposals to solve the electric charge quantization
puzzle, which simultaneously explain the recent measured deviation on the muon
anomalous magnetic moment. For this we assess extensions of the Electro-Weak
Standard Model spanning modifications on the scalar sector only. It is
interesting to verify that one can have modest extensions which easily account
for the solution for both problems.Comment: 20 pages, 1 figures, needs macro axodraw.st
Two-loop Barr-Zee type Contributions to in the MSSM
We consider the contribution of a two-loop Barr-Zee type diagram to
in the minimal supersymmetric standard model (MSSM). At relatively
large , we show that the contribution of light third generation
scalar fermions and neutral CP-even Higgs, , can easily explain the
very recent BNL experimental data. In our analysis prefers negative
and positive . It is more sensitive to the chirality flipping
h^0(H^0)\wt{f}_R^*\wt{f}_L rather than chirality conserving couplings.Comment: 10 pages, 5 figures, references adde
QCD corrections to plus -boson production at the LHC
The associated production at the LHC is an important process in
investigating the color-octet mechanism of non-relativistic QCD in describing
the processes involving heavy quarkonium. We calculate the next-to-leading
order (NLO) QCD corrections to the associated production at the
LHC within the factorization formalism of nonrelativistic QCD, and provide the
theoretical predictions for the distribution of the transverse
momentum. Our results show that the differential cross section at the
leading-order is significantly enhanced by the NLO QCD corrections. We conclude
that the LHC has the potential to verify the color-octet mechanism by measuring
the production events.Comment: 14 page revtex, 5 eps figures, to appear in JHEP. fig5 and the
corresponding analysis are correcte
Dualities and the phase diagram of the -clock model
A new "bond-algebraic" approach to duality transformations provides a very
powerful technique to analyze elementary excitations in the classical
two-dimensional XY and -clock models. By combining duality and Peierls
arguments, we establish the existence of non-Abelian symmetries, the phase
structure, and transitions of these models, unveil the nature of their
topological excitations, and explicitly show that a continuous U(1) symmetry
emerges when . This latter symmetry is associated with the appearance
of discrete vortices and Berezinskii-Kosterlitz-Thouless-type transitions. We
derive a correlation inequality to prove that the intermediate phase, appearing
for , is critical (massless) with decaying power-law correlations.Comment: 48 pages, 5 figures. Submitted to Nuclear Physics
Yukawa coupling unification and non-universal gaugino mediation of supersymmetry breaking
The requirement of Yukawa coupling unification highly constrains the SUSY
parameter space. In several SUSY breaking scenarios it is hard to reconcile
Yukawa coupling unification with experimental constraints from B(b->s gamma)
and the muon anomalous magnetic moment a_mu. We show that b-tau or even t-b-tau
Yukawa unification can be satisfied simultaneously with b->s gamma and a_mu in
the non-universal gaugino mediation scenario. Non-universal gaugino masses
naturally appear in higher dimensional grand unified models in which gauge
symmetry is broken by orbifold compactification. Relations between SUSY
contributions to fermion masses, b->s gamma and a_mu which are typical for
models with universal gaugino masses are relaxed. Consequently, these
phenomenological constraints can be satisfied simultaneously with a relatively
light SUSY spectrum, compared to models with universal gaugino masses.Comment: 20 pages, 8 figures. References added. A copy of the paper with
better resolution figures can be found at
http://www.hep.fsu.edu/~balazs/Physics/Papers/2003
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