1,721,025 research outputs found
The Electroweak phase transition in models with gauge-Higgs unification
Full text linkThe dynamics of five dimensional Wilson line phases at finite temperature is studied in the oneloop approximation. We show that at temperatures of order T ∼ 1/L, where L is the length of
the compact space, the gauge symmetry is always restored and the electroweak phase transition
appears to be of first order.
We focus on a specific model where the Wilson line phase is identified with the Higgs field
(gauge-Higgs unification). The transition is of first order even for values of the Higgs mass above
the current experimental limit. If large localized gauge kinetic terms are present, the transition
might be strong enough to give baryogenesis at the electroweak transitio
A model of electroweak symmetry breaking from a fifth dimension
No full textWe reconsider the idea of identifying the Higgs field as the internal component
of a gauge field in the flat space ,
by relaxing the constraint of having unbroken SO(4,1) Lorentz symmetry in the bulk.
In this way, we show that the main common problems of previous models of this sort,
namely the prediction of a too light Higgs and top mass, as well as of a too low
compactification scale, are all solved. We mainly focus our attention on a
previously constructed model.
We show how, with few minor modifications and by relaxing the requirement
of SO(4,1) symmetry, a potentially realistic model can be obtained with a moderate
tuning in the parameter space of the theory. In this model,
the Higgs potential is stabilized and the hierarchy of fermion masses explained
Conformality Loss, Walking, and 4D Complex Conformal Field Theories at Weak Coupling
Full text linkFour-dimensional gauge theories with matter can have regions in parameter space, often dubbed conformal windows, where they flow in the infrared to nontrivial conformal field theories. It has been conjectured that conformality can be lost because of merging of two nearby fixed points that move into the complex plane, and that a walking dynamics governed by scaling dimensions of operators defined at such complex fixed points can occur. We find controlled, parametrically weakly coupled, and ultraviolet-complete 4D gauge theories that explicitly realize this scenario. We show how the walking dynamics is controlled by the coupling of a double-trace operator that crosses marginality. The walking regime ends when the renormalization group flow of this coupling leads to a (weak) first-order phase transition with Coleman-Weinberg symmetry breaking. A light dilatonlike scalar particle appears in the spectrum, but it is not parametrically lighter than the other excitations
Resurgence and 1/N Expansion in Integrable Field Theories
Full text linkIn theories with renormalons the perturbative series is factorially divergent even after restricting to a given order in 1/N, making the 1/N expansion a natural testing ground for the theory of resurgence. We study in detail the interplay between resurgent properties and the 1/N expansion in various integrable field theories with renormalons. We focus on the free energy in the presence of a chemical potential coupled to a conserved charge, which can be computed exactly with the thermodynamic Bethe ansatz (TBA). In some examples, like the first 1/N correction to the free energy in the non-linear sigma model, the terms in the 1/N expansion can be fully decoded in terms of a resurgent trans-series in the coupling constant. In the principal chiral field we find a new, explicit solution for the large N free energy which can be written as the median resummation of a trans-series with infinitely many, analytically computable IR renormalon corrections. However, in other examples, like the Gross-Neveu model, each term in the 1/N expansion includes non-perturbative corrections which can not be predicted by a resurgent analysis of the corresponding perturbative series. We also study the properties of the series in 1/N. In the Gross-Neveu model, where this is convergent, we analytically continue the series beyond its radius of convergence and show how the continuation matches with known dualities with sine-Gordon theories
A note on the torsion dependence of D-brane RR couplings
No full textThe dependence on the torsion H = db of the Wess-Zumino couplings of D-branes that are trivially embedded in space-time is studied. We show that even in this simple set-up some torsion components can be turned on, with a non-trivial effect on the RR couplings. In the special cases in which either the tangent or the normal bundle are trivial, the torsion dependence amounts to substitute the standard curvature with its generalization in the presence of torsion, in the usual couplings involving the roof genus Â. © 2001 Elsevier Science B. V
A Monte Carlo approach to the conformal bootstrap
No full textWe introduce an approach to find approximate numerical solutions of truncated bootstrap equations for conformal field theories (CFTs) in arbitrary dimensions. The method is based on a stochastic search via a Metropolis algorithm guided by an action S which is the logarithm of the truncated bootstrap equations for a single scalar field correlator. While numerical conformal bootstrap methods based on semidefinite programming put rigorous exclusion bounds on CFTs, this method looks for approximate solutions, which correspond to local minima of S, when present, and can be even far from the extremality region. By this protocol we find that if no constraint on the operator scaling dimensions is imposed, S has a single minimum, corresponding to the free theory. If we fix the external operator dimension, however, we encounter minima that can be studied with our approach. Imposing a conserved stress-tensor, a Z(2) symmetry and one relevant scalar, we identify two regions where local minima of S are present. When projected in the (Delta(sigma), Delta(epsilon))-plane, sigma and epsilon being the external and the lightest exchanged operators, one of these regions essentially coincides with the extremality line found in previous bootstrap studies. The other region is along the generalized free theories in d = 2 and below that in both d = 3 and d = 4. We empirically prove that some of the minima found are associated to known theories, including the 2d and 3d Ising theories and the 2d Yang-Lee model
Electroweak Symmetry Breaking and Precision Tests with a Fifth Dimension
No full textWe perform a complete study of flavour and CP conserving electroweak observables in
a slight refinement of a recently proposed five--dimensional model
on , where the Higgs is the internal component
of a gauge field and the Lorentz symmetry is broken in the fifth dimension.
Interestingly enough, the relevant corrections to the electroweak
observables turn out to be of universal type and
essentially depend only on the value of the Higgs mass
and on the scale of new physics, in our case the compactification scale .
The model passes all constraints for TeV at 90 C.L., with a moderate
fine--tuning in the parameters.
The Higgs mass turns out to be always smaller than 200 GeV although higher values
would be allowed, due to a large correction to the parameter.
The lightest non-SM states in the model are typically colored fermions with a mass
of order TeV
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