30,227 research outputs found

### Higgs Localization in Split Fermion Models

The flavor puzzle of the Standard Model is explained in split fermion models
by having the fermions localized and separated in an extra dimension. Many of
these models assume a certain profile for the Higgs VEV, usually uniform, or
confined to a brane, without providing a dynamical realization for it. By
studying the effect of the coupling between the Higgs and the localizer fields,
we obtain these scenarios as results, rather than ansaetze. Moreover, we
discuss other profiles and show that they are phenomenologically viable.Comment: 23 pages, 16 figures, based on an MSc thesi

### Quantum Fermion Hair

It is shown that the Dirac operator in the background of a magnetic
%Reissner-Nordstr\"om black hole and a Euclidean vortex possesses normalizable
zero modes in theories containing superconducting cosmic strings. One
consequence of these zero modes is the presence of a fermion condensate around
magnetically charged black holes which violates global quantum numbers.Comment: 16pp (harvmac (l)) and 2 figs.(not included

### Ultraviolet Properties of the Higgs Sector in the Lee-Wick Standard Model

The Lee-Wick (LW) Standard Model (SM) offers a new solution to the hierarchy
problem. We discuss, using effective potential techniques, its peculiar
ultraviolet (UV) behaviour. We show how quadratic divergences in the Higgs mass
Mh cancel as a result of the unusual dependence of LW fields on the Higgs
background (in a manner reminiscent of Little Higgses). We then extract from
the effective potential the renormalization group evolution of the Higgs
quartic coupling lambda above the LW scale. After clarifying an apparent
discrepancy with previous results for the LW Abelian Higgs model we focus on
the LWSM. In contrast with the SM case, for any Mh, lambda grows monotonically
and hits a Landau pole at a fixed trans-Planckian scale (never turning negative
in the UV). Then, the perturbativity and stability bounds on Mh disappear. We
identify a cutoff ~10^{16} GeV for the LWSM due to the hypercharge gauge
coupling hitting a Landau pole. Finally, we also discuss briefly the possible
impact of the UV properties of the LW models on their behaviour at finite
temperature, in particular regarding symmetry nonrestoration.Comment: 25 pages, 3 figure

### The analysis of temporal variations in regional models of the Sargasso Sea from GEOS-3 altimetry

The dense coverage of short pulse mode GEOS-3 altimeter data in the western North Atlantic provides a basis for studying time variations in the sea surface heights in the Sargasso Sea. Two techniques are utilized: the method of regional models, and the analysis of overlapping passes. An 88 percent correlation is obtained between the location of cyclonic eddies obtained from infrared imagery and sea surface height minima in the altimeter models. This figure drops to 59 percent in the case of correlations with maxima and minima of surface temperature fields. The analysis of overlapping passes provides a better picture of instantaneous sea state through wavelengths greater than 30 km. The variability of the Sargasso Sea through wavelengths between 150 km and 5000 km is estimated at + or - 28 cm. This value is in reasonable agreement with oceanographic estimates and is compatible with the eddy kinetic energy of a wind driven circulation

### Factors Affecting Trade in Mexican Imports of Poultry Meat from the United States

U.S. exports of poultry to Mexico have increased steadily since NAFTA came into force in January 1994. The Mexican poultry industry has become increasingly concerned about these exports, arguing that it cannot compete with U.S. products. The Mexicans argue that U.S. poultry exports to Mexico are duty free under NAFTA (as of January 1, 2003). The Mexican industry also argues that U.S. poultry benefits from low-priced feed resulting from U.S. Government farm programs. We analyzed the impact of tariffs and U.S. feed grain programs on U.S. exports of poultry, and find that other factors appear to be more important in explaining trade. Specifically, Mexican preferences for dark meat provide large price incentives for U.S. exporters, while Mexican Government policies in support of its grain sector penalize poultry producers in Mexico.International Relations/Trade,

### Vacuum Decay in Theories with Symmetry Breaking by Radiative Corrections

The standard bounce formalism for calculating the decay rate of a metastable
vacuum cannot be applied to theories in which the symmetry breaking is due to
radiative corrections, because in such theories the tree-level action has no
bounce solutions. In this paper I derive a modified formalism to deal with such
cases. As in the usual case, the bubble nucleation rate may be written in the
form $A e^{-B}$. To leading approximation, $B$ is the bounce action obtained by
replacing the tree-level potential by the leading one-loop approximation to the
effective potential, in agreement with the generally adopted {\it ad hoc}
remedy. The next correction to $B$ (which is proportional to an inverse power
of a small coupling) is given in terms of the next-to-leading term in the
effective potential and the leading correction to the two-derivative term in
the effective action. The corrections beyond these (which may be included in
the prefactor) do not have simple expressions in terms of the effective
potential and the other functions in the effective action. In particular, the
scalar-loop terms which give an imaginary part to the effective potential do
not explicitly appear; the corresponding effects are included in a functional
determinant which gives a manifestly real result for the nucleation rate.Comment: 39 pages, CU-TP-57

### Fate of the false monopoles: induced vacuum decay

We study a gauge theory model where there is an intermediate symmetry
breaking to a meta- stable vacuum that breaks a simple gauge group to a U (1)
factor. Such models admit the existence of meta-stable magnetic monopoles,
which we dub false monopoles. We prove the existence of these monopoles in the
thin wall approximation. We determine the instantons for the collective
coordinate that corresponds to the radius of the monopole wall and we calculate
the semi-classical tunneling rate for the decay of these monopoles. The
monopole decay consequently triggers the decay of the false vacuum. As the
monopole mass is increased, we find an enhanced rate of decay of the false
vacuum relative to the celebrated homogeneous tunneling rate due to Coleman
[1].Comment: 10 pages, 4 figure

### Baryon Asymmetry in a Heavy Moduli Scenario

In some models of supersymmetry breaking, modulus fields are heavy enough to
decay before BBN. But the large entropy produced via moduli decay significantly
dilutes the preexisting baryon asymmetry of the universe. We study whether
Affleck-Dine mechanism can provide enough baryon asymmetry which survives the
dilution, and find several situations in which desirable amount of baryon
number remains after the dilution. The possibility of non-thermal dark matter
is also discussed. This provides the realistic cosmological scenario with heavy
moduli.Comment: 36 pages, 5 figures; added a reference; v3: minor correction

### Scaling tests with dynamical overlap and rooted staggered fermions

We present a scaling analysis in the 1-flavor Schwinger model with the full
overlap and the rooted staggered determinant. In the latter case the chiral and
continuum limit of the scalar condensate do not commute, while for overlap
fermions they do. For the topological susceptibility a universal continuum
limit is suggested, as is for the partition function and the Leutwyler-Smilga
sum rule. In the heavy-quark force no difference is visible even at finite
coupling. Finally, a direct comparison between the complete overlap and the
rooted staggered determinant yields evidence that their ratio is constant up to
$O(a^2)$ effects.Comment: 28 pages, 20 figures containg 37 graphs. v2: 6 new references, 2 new
footnotes (to match published version

### Space Time Foam: a ground state candidate for Quantum Gravity

A model of space-time foam, made by $N$ wormholes is considered. The Casimir
energy leading to such a model is computed by means of the phase shift method
which is in agreement with the variational approach used in Refs.[9-14]. The
collection of Schwarzschild and Reissner-Nordstr\"{o}m wormholes are separately
considered to represent the foam. The Casimir energy shows that the
Reissner-Nordstr\"{o}m wormholes cannot be used to represent the foam.Comment: 6 pages.RevTeX with package epsf and two eps figures. To be submitted
to the proceedings of the 4th Workshop of `Mysteries, Puzzles And Paradoxes
In Quantum Mechanics' Gargnano (Italy), 27 August-1 September 200

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