17,067 research outputs found
Upper limit on mh in the MSSM and M-SUGRA vs. prospective reach of LEP
The upper limit on the lightest CP-even Higgs boson mass, mh, is analyzed
within the MSSM as a function of tan(beta) for fixed mtop and Msusy. The impact
of recent diagrammatic two-loop results on this limit is investigated. We
compare the MSSM theoretical upper bound on mh with the lower bound obtained
from experimental searches at LEP. We estimate that with the LEP data taken
until the end of 1999, the region mh < 108.2 GeV can be excluded at the 95%
confidence level. This corresponds to an excluded region 0.6 <= tan(beta) <=
1.9 within the MSSM for mtop = 174.3 GeV and Msusy <= 1 TeV. The final
exclusion sensitivity after the end of LEP, in the year 2000, is also briefly
discussed. Finally, we determine the upper limit on mh within the Minimal
Supergravity (M-SUGRA) scenario up to the two-loop level, consistent with
radiative electroweak symmetry breaking. We find an upper bound of mh \approx
127 GeV for mtop = 174.3 GeV in this scenario, which is slightly below the
bound in the unconstrained MSSM.Comment: 10 pages, 3 figure
Bounds on the Simplest Little Higgs Model Mass Spectrum Through Z Leptonic Decay
We derive the leptonic neutral current in the simplest little Higgs model and
compute the contribution of the model to the decay width . Using
the precision electroweak data we obtain a strong lower bound TeV
at 95% C.L. on the characteristic energy scale of the model. It results in a
lower bound for the new gauge bosons and as being
TeV and TeV, respectively.
We also present the allowed values of the which is the parameter
relating the two vacuum expectation values of the scalar triplets in the model,
and the parameter of a quadratic term, involving the triplets, necessary
to provide an acceptable mass range for the standard Higgs boson.Comment: New references added, 13 pages. Version to be publishe
Scaling limit for a drainage network model
We consider the two dimensional version of a drainage network model
introduced by Gangopadhyay, Roy and Sarkar, and show that the appropriately
rescaled family of its paths converges in distribution to the Brownian web. We
do so by verifying the convergence criteria proposed by Fontes, Isopi, Newman
and Ravishankar.Comment: 15 page
Regularity at infinity of real mappings and a Morse-Sard theorem
We prove a new Morse-Sard type theorem for the asymptotic critical values of
semi-algebraic mappings and a new fibration theorem at infinity for
mappings. We show the equivalence of three different types of regularity
conditions which have been used in the literature in order to control the
asymptotic behaviour of mappings. The central role of our picture is played by
the -regularity and its bridge toward the -regularity which implies
topological triviality at infinity
Untangling Fine-Grained Code Changes
After working for some time, developers commit their code changes to a
version control system. When doing so, they often bundle unrelated changes
(e.g., bug fix and refactoring) in a single commit, thus creating a so-called
tangled commit. Sharing tangled commits is problematic because it makes review,
reversion, and integration of these commits harder and historical analyses of
the project less reliable. Researchers have worked at untangling existing
commits, i.e., finding which part of a commit relates to which task. In this
paper, we contribute to this line of work in two ways: (1) A publicly available
dataset of untangled code changes, created with the help of two developers who
accurately split their code changes into self contained tasks over a period of
four months; (2) a novel approach, EpiceaUntangler, to help developers share
untangled commits (aka. atomic commits) by using fine-grained code change
information. EpiceaUntangler is based and tested on the publicly available
dataset, and further evaluated by deploying it to 7 developers, who used it for
2 weeks. We recorded a median success rate of 91% and average one of 75%, in
automatically creating clusters of untangled fine-grained code changes
Dynamically Induced Spontaneous Symmetry Breaking in 3-3-1 Models
We show that in SU(3)_C X SU(3)_L X U(1)_N (3-3-1) models embedded with a
singlet scalar playing the role of the axion, after imposing scale invariance,
dynamical symmetry breaking of Peccei-Quinn symmetry occurs through the
one-loop effective potential for the singlet field. We, then, analyze the
structure of spontaneous symmetry breaking by studying the new scalar potential
for the model, and verify that electroweak symmetry breaking is tightly
connected to the 3-3-1 breaking by the strong constraints among their vacuum
expectation values. This offers a valuable guide to write down the correct
pattern of symmetry breaking for multi-scalar theories. We also obtained that
the accompanying massive pseudo-scalar, instead of acquiring mass of order of
Peccei-Quinn scale as we would expect, develops a mass at a much lower scale, a
consequence solely of the dynamical breaking.Comment: 12 pages, typos corrected, improved text, conclusions unchange
The Left-Right SU(3)(L)xSU(3)(R)xU(1)(X) Model with Light, keV and Heavy Neutrinos
We construct a full left-right model for the electroweak interactions based
on the gauge symmetry. The fermion
content of the model is such that anomaly cancellation restricts the number of
families to be a multiple of three. One of the most important features of the
model is the joint presence of three light active neutrinos, three additional
neutrinos at keV mass scale, and six heavy ones with masses
around\textbf{} GeV. They form a well-motivated part of the spectrum
in the sense they address challenging problems related to neutrino oscillation,
warm dark matter, and baryogenesis through leptogenesis.Comment: 11 pages. Small corrections and typos fixed. Accepted for publication
in PR
Spin filtering in nanowire directional coupler
The spin transport characteristics of a nanowire directional electronic
coupler have been evaluated theoretically via a transfer matrix approach. The
application of a gate field in the region of mixing allows for control of spin
current through the different leads of the coupler via the Rashba spin-orbit
interaction. The combination of spin-orbit interaction and applied gate
voltages on different legs of the coupler give rise to a controllable
modulation of the spin polarization. Both structural factors and field strength
tuning lead to a rich phenomenology that could be exploited in spintronic
devices.Comment: 9 pages, 4 figure
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