398 research outputs found
Kink modes and effective four dimensional fermion and Higgs brane models
In the construction of a classical smoothed out brane world model in five
dimensions, one uses a dynamically generated domain wall (a kink) to localise
an effective four dimensional theory. At the level of the Euler-Lagrange
equations the kink sets up a potential well, a mechanism which has been
employed extensively to obtain localised, four dimensional, massless chiral
fermions. We present the generalisation of this kink trapping mechanism for
both scalar and fermionic fields, and retain all degrees of freedom that were
present in the higher dimensional theory. We show that a kink background
induces a symmetric modified Poschl-Teller potential well, and give explicit
analytic forms for all the bound modes and a restricted set of the continuum
modes. We demonstrate that it is possible to confine an effective four
dimensional scalar field with a quartic potential of arbitrary shape. This can
be used to place the standard model electroweak Higgs field on the brane, and
also generate nested kink solutions. We also consider the limits of the
parameters in the theory which give thin kinks and localised and de-localised
scalar and fermionic fields.Comment: 25 pages, REVTeX4 preprint; v2: added appendix B and made minor other
changes to thoroughly explain the kink zero mode dynamic
Quantum corrections in Higgs inflation: the real scalar case
We present a critical discussion of quantum corrections, renormalisation, and
the computation of the beta functions and the effective potential in Higgs
inflation. In contrast with claims in the literature, we find no evidence for a
disagreement between the Jordan and Einstein frames, even at the quantum level.
For clarity of discussion we concentrate on the case of a real scalar Higgs. We
first review the classical calculation and then discuss the back reaction of
gravity. We compute the beta functions for the Higgs quartic coupling and
non-minimal coupling constant. Here, the mid-field regime is
non-renormalisable, but we are able to give an upper bound on the 1-loop
corrections to the effective potential. We show that, in computing the
effective potential, the Jordan and Einstein frames are compatible if all mass
scales are transformed between the two frames. As such, it is consistent to
take a constant cutoff in either the Jordan or Einstein frame, and both
prescriptions yield the same result for the effective potential. Our results
are extended to the case of a complex scalar Higgs.Comment: 28 pages, 1 figure. v2: minor changes, updated references, published
versio
Stability of domain walls coupled to Abelian gauge fields
Rozowsky, Volkas and Wali recently found interesting numerical solutions to
the field equations for a gauged U1xU1 scalar field model. Their solutions
describe a reflection-symmetric domain wall with scalar fields and coupled
gauge configurations that interpolate between constant magnetic fields on one
side of the wall and exponentially decaying ones on the other side. This
corresponds physically to an infinite sheet of supercurrent confined to the
domain wall with a linearly rising gauge potential on one side and Meissner
suppression on the other. While it was shown that these static solutions
satisfied the field equations, their stability was left unresolved. In this
paper, we analyse the normal modes of perturbations of the static solutions to
demonstrate their perturbative stability.Comment: 9 pages, 9 figure
Investigating Multiple Solutions in the Constrained Minimal Supersymmetric Standard Model
Recent work has shown that the Constrained Minimal Supersymmetric Standard
Model (CMSSM) can possess several distinct solutions for certain values of its
parameters. The extra solutions were not previously found by public
supersymmetric spectrum generators because fixed point iteration (the algorithm
used by the generators) is unstable in the neighbourhood of these solutions.
The existence of the additional solutions calls into question the robustness of
exclusion limits derived from collider experiments and cosmological
observations upon the CMSSM, because limits were only placed on one of the
solutions. Here, we map the CMSSM by exploring its multi-dimensional parameter
space using the shooting method, which is not subject to the stability issues
which can plague fixed point iteration. We are able to find multiple solutions
where in all previous literature only one was found. The multiple solutions are
of two distinct classes. One class, close to the border of bad electroweak
symmetry breaking, is disfavoured by LEP2 searches for neutralinos and
charginos. The other class has sparticles that are heavy enough to evade the
LEP2 bounds. Chargino masses may differ by up to around 10% between the
different solutions, whereas other sparticle masses differ at the sub-percent
level. The prediction for the dark matter relic density can vary by a hundred
percent or more between the different solutions, so analyses employing the dark
matter constraint are incomplete without their inclusion.Comment: 30 pages, 12 figures, 2 tables; v2: added discussion on speed of
shooting method, fixed typos, matches published versio
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