396 research outputs found
Equivalence of the sine-Gordon and massive Thirring models at finite temperature
Using the path-integral approach, the quantum massive Thirring and
sine-Gordon models are proven to be equivalent at finite temperature. This
result is an extension of Coleman's proof of the equivalence between both
theories at zero temperature. The usual identifications among the parameters of
these models also remain valid at .Comment: 9 pages, standard LaTe
Dynamical Symmetry Breaking With a Fourth Generation
Adding a fourth generation to the Standard Model and assuming it to be valid
up to some cutoff \Lambda, we show that electroweak symmetry is broken by
radiative corrections due to the fourth generation. The effects of the fourth
generation are isolated using a Lagrangian with a genuine scalar without
self-interactions at the classical level. For masses of the fourth generation
consistent with electroweak precision data (including the B \rightarrow K \pi\
CP asymmetries) we obtain a Higgs mass of the order of a few hundreds GeV and a
cutoff \Lambda\ around 1-2 TeV. We study the reliability of the perturbative
treatment used to obtain these results taking into account the running of the
Yukawa couplings of the fourth quark generation with the aid of the
Renormalization Group (RG) equations, finding similar allowed values for the
Higgs mass but a slightly lower cut-off due to the breaking of the perturbative
regime. Such low cut-off means that the effects of new physics needed to
describe electroweak interactions at energy above \Lambda\ should be measurable
at the LHC. We use the minimal supersymmetric extension of the standard model
with four generations as an explicit example of models realizing the dynamical
electroweak symmetry breaking by radiative corrections and containing new
physics. Here, the cutoff is replaced by the masses of the squarks and
electroweak symmetry breaking by radiative corrections requires the squark
masses to be of the order of 1 TeV.Comment: 20 pages, 7 figures. New section adde
Is the standard Higgs scalar elementary?
In the standard electroweak model, the measured top quark mass requires a
sizeable Yukawa coupling to the fundamental scalar. This large coupling alone
might induce a dynamical breaking of the electroweak symmetry as well as
non-perturbative effects. If such is the case, even a standard Higgs scalar as
light as 80 GeV should have a non-negligible component induced by
the top condensate.Comment: 8 pages, Latex fil
A Dynamical scheme for a large CP violating phase
A dynamical scheme where the third generation of quarks plays a distinctive
role is implemented. New interactions with a term induce the breaking
of the electroweak symmetry and the top-bottom mass splitting. A large
CP-violating phase naturally follows from the latter.
Comment: 10 pages, LaTe
A sharp incisor tool for predator house mice back to the wild
The house mouse (Mus musculus domesticus), as a successful invasive species worldwide, has to forage a variety of resources. Subantarctic mice display among the most notable diet shift from the usual omnivorous–granivorous diet, relying on a larger proportion of terrestrial animal prey. In agreement, a recent study of their mandible morphology evidenced an evolution of their mandible shape to optimize incisor biting and hence seize preys. Here, the incisors themselves are the focus of a morphometric analysis combined with a 3D study of their internal structure, aiming at a comparison between subantarctic populations (Guillou island, Kerguelen archipelago) with a range of western European continental, commensal mice. The predatory foraging behavior of Guillou mice was indeed associated with a sharper bevel of the lower incisor, which appears as an efficient morphology for piercing prey. The incisor of these mice also displays a reduced pulp cavity, suggesting slower eruption counterbalancing a reduced abrasion on such soft food material. The dynamics of the ever‐growing incisor may thus allow adaptive incisor sculpting and participate to the success of mice in foraging diverse resources
XXZ spin chain in transverse field as a regularization of the sine-Gordon model
We consider here XXZ spin chain perturbed by the operator sigma^x (``in
transverse field'') which is a lattice regularization of the sine-Gordon model.
This can be shown using conformal perturbation theory. We calculated mass
ratios of particles which lie in a discrete part of the spectrum and obtained
results in accord with the DHN formula and in disagreement with recent
calculations in literature based on numerical Bethe Ansatz and infinite
momentum frame methods. We also analysed a short distance behavior of this
states (UV or conformal limit). Our result for conformal dimension of the
second breather state is different from the conjecture in [Klassen and Melzer,
Int. J. Mod. Phys. A8, 4131 (1993)] and is consistent with this paper for other
states.Comment: 7 pages, REVTeX, 6 figures, to appear in Phys. Rev.
Supersymmetric contributions to and decays in SCET
We study the decay modes and using Soft Collinear Effective Theory. Within Standard Model and
including the error due to the SU(3) breaking effect in the SCET parameters we
find that BR and BR
corresponding to
solution 1 and solution 2 of the SCET parameters respectively.For the decay
mode , we find that BR and BR corresponding to solution 1 and
solution 2 of the SCET parameters respectively. We extend our study to include
supersymmetric models with non-universal A-terms where the dominant
contributions arise from diagrams mediated by gluino and chargino exchanges. We
show that gluino contributions can not lead to an enhancement of the branching
ratios of and . In
addition, we show that SUSY contributions mediated by chargino exchange can
enhance the branching ratio of by about 14% with
respect to the SM prediction. For the branching ratio of , we find that SUSY contributions can enhance its value by about 1% with
respect to the SM prediction.Comment: 25 pages,5 figures, version accepted for publicatio
Properties of the massive Thirring model from the XYZ spin chain
We consider here the massive Thirring model regularized with the XYZ spin
chain. We numerically calculate the mass ratios of particles which lie in the
discrete part of the spectrum and obtain results in accordance with the DHN
formula and in disagreement with recent calculations in the literature based on
the numerical Bethe ansatz and infinite momentum frame methods. We also analyze
the short distance behavior of these states and evaluate the conformal
dimensions. This paper, taken together with the previous one for the
sine-Gordon model, confirms the duality relation between two models formulated
by Klassen and Melzer [Int. J. Mod. Phys. A 8, 4131 (1993)].Comment: 11 pages, 6 figures, to be published in Phys. Rev. D 6
Novel sources of Flavor Changed Neutral Currents in the model
Sources of Flavor Changed Neutral Currents (FCNC) naturally emerge from a
well motivated framework called 3-3-1 with right-handed neutrinos model,
for short, mediated by an extra neutral gauge boson .
Following previous works we calculate these sources and in addition we derive
new ones coming from CP-even and -odd neutral scalars which appear due to their
non-diagonal interactions with the physical standard quarks. Furthermore we
show that bounds related to the neutral mesons systems and may be significantly strengthened in the presence of these new
interactions allowing us to infer stronger constraints on the parameter space
of the model.Comment: Published version. 10 pages, 6 figure
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