11,794 research outputs found
A Slant on Warped Extra Dimensions
We propose an orbifolded, warped, extra dimension scenario in which the
visible brane is not parallel to the hidden brane. This leads automatically to
Lorentz violation in the visible, four dimensional world. The background
solution to the Einstein equations is a function of a parameter that can be
identified with the amount of 'tilting' of the brane. The cosmological constant
is found to coincide with the classic Randall-Sundrum value to first order in
this tilt. Lorentz violating effects induced in the Standard Model are
considered. We find that the strongest constraint on the tilt comes from
determinations of the electron-proton mass ratio in six quasar spectra (four
optical and two radio). Measurements of a third radio source could improve this
by an order of magnitude.Comment: 13 pages, no figure
Baryogenesis from the Kobayashi-Maskawa Phase
The Standard Model fulfills the three Sakharov conditions for baryogenesis.
The smallness of quark masses suppresses, however, the CP violation from the
Kobayashi-Maskawa phase to a level that is many orders of magnitude below what
is required to explain the observed baryon asymmetry. We point out that if, as
a result of time variation in the Yukawa couplings, quark masses were large at
the time of the electroweak phase transition, then the Kobayashi-Maskawa
mechanism could be the source of the asymmetry. The Froggatt-Nielsen mechanism
provides a plausible framework where the Yukawa couplings could all be of order
one at that time, and settle to their present values before nucleosynthesis.
The problems related to a strong first order electroweak phase transition may
also be alleviated in this framework. Our scenario reveals a loophole in the
commonly held view that the Kobayashi-Maskawa mechanism cannot be the dominant
source of CP violation to play a role in baryogenesis.Comment: 4 page
Self-Consistent Field Theory of Multiply-Branched Block Copolymer Melts
We present a numerical algorithm to evaluate the self-consistent field theory
for melts composed of block copolymers with multiply-branched architecture. We
present results for the case of branched copolymers with doubly-functional
groups for multiple branching generations. We discuss the stability of the
cubic phase of spherical micelles, the A15 phase, as a consequence of tendency
of the AB interfaces to conform to the polyhedral environment of the Voronoi
cell of the micelle lattice.Comment: 12 pages, 10 includes figure
Wave function of the radion in a brane world
We calculate the linearized metric perturbation corresponding to a massless
four-dimensional scalar field, the radion, in a five-dimensional two-brane
model of Randall and Sundrum. In this way we obtain relative strengths of the
radion couplings to matter residing on each of the branes. The results are in
agreement with the analysis of Garriga and Tanaka of gravitational and
Brans--Dicke forces between matter on the branes. We also introduce a model
with infinite fifth dimension and ``almost'' confined graviton, and calculate
the radion properties in that model.Comment: 5 pages revtex, no figures, equation correcte
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