2,425 research outputs found
Dynamical Fermion Masses Under the Influence of Kaluza-Klein Fermions and a Bulk Abelian Gauge Field
The dynamical fermion mass generation on a 3-brane in the 5D space-time is
discussed in a model with bulk fermions in interaction with fermions on the
brane assuming the presence of a constant abelian gauge field component
in the bulk. We calculate the effective potential as a function of the fermion
masses and the gauge field component . The masses can be found from the
stationarity condition for the effective potential (the gap equation). We
formulate the equation for the mass spectrum of the 4D--fermions. The phases
with finite and vanishing fermion masses are studied and the dependence of the
masses on the radius of the 5th dimension is analyzed. The influence of the
-component of the gauge field on the symmetry breaking is considered both
when this field is a background parameter and a dynamical variable. The
critical values of the field, the coupling constant and the radius are
examined.Comment: 9 pages, 4 figure
Second order brane cosmology with radion stabilization
We study cosmology in the five-dimensional Randall-Sundrum brane-world with a
stabilizing effective potential for the radion and matter localized on the
branes. The analysis is performed by employing a perturbative expansion in the
ratio rho/V between the matter energy density on the branes and the brane
tensions around the static Randall-Sundrum solution (which has rho=0 and brane
tensions +-V). This approach ensures that the matter evolves adiabatically and
allows us to find approximate solutions to second order in \rho/V. Some
particular cases are then analyzed in details.Comment: 17 pages, RevTeX4, 4 figures, final version to appear in Phys. Rev.
Radion stabilization from the vacuum on flat extra dimensions
Volume stabilization in models with flat extra dimension could follow from
vacuum energy residing in the bulk when translational invariance is
spontaneously broken. We study a simple toy model that exemplifies this
mechanism which considers a massive scalar field with non trivial boundary
conditions at the end points of the compact space, and includes contributions
from brane and bulk cosmological constants. We perform our analysis in the
conformal frame where the radion field, associated with volume variations, is
defined, and present a general strategy for building stabilization potentials
out of those ingredients. We also provide working examples for the interval and
the orbifold configuration.Comment: Comments and clarifications added throughout the text. Typos
corrected and references added. Final version, 27 pages, five figures
include
General features of Bianchi-I cosmological models in Lovelock gravity
We derived equations of motion corresponding to Bianchi-I cosmological models
in the Lovelock gravity. Equations derived in the general case, without any
specific ansatz for any number of spatial dimensions and any order of the
Lovelock correction. We also analyzed the equations of motion solely taking
into account the highest-order correction and described the drastic difference
between the cases with odd and even numbers of spatial dimensions. For
power-law ansatz we derived conditions for Kasner and generalized Milne regimes
for the model considered. Finally, we discuss the possible influence of matter
in the form of perfect fluid on the solutions obtained.Comment: extended version of published Brief Repor
First Order Calculation of the Inclusive Cross Section pp to ZZ by Graviton Exchange in Large Extra Dimensions
We calculate the inclusive cross section of double Z-boson production within
large extra dimensions at the Large Hadron Collider (LHC). Using perturbatively
quantized gravity in the ADD model we perform a first order calculation of the
graviton mediated contribution to the pp to ZZ cross section. At low energies
(e.g. Tevatron) this additional contribution is very small, making it virtually
unobservable, for a fundamental mass scale above 2500 GeV. At LHC energies
however, the calculation indicates that the ZZ-production rate within the ADD
model should differ significantly from the Standard Model if the new
fundamental mass scale would be below 15000 GeV. A comparison with the observed
production rate at the LHC might therefore provide direct hints on the number
and structure of the extra dimensions.Comment: 7 pages, 7 figures, accepted for publication in Phys. Rev.
Massive color-octet bosons and the charge asymmetries of top quarks at hadron colliders
Several models predict the existence of heavy colored resonances decaying to
top quarks in the TeV energy range that might be discovered at the LHC. In some
of those models, moreover, a sizable charge asymmetry of top versus antitop
quarks might be generated. The detection of these exotic resonances, however,
requires selecting data samples where the top and the antitop quarks are highly
boosted, which is experimentally very challenging. We asses that the
measurement of the top quark charge asymmetry at the LHC is very sensitive to
the existence of excited states of the gluon with axial-vector couplings to
quarks. We use a toy model with general flavour independent couplings, and show
that a signal can be detected with relatively not too energetic top and antitop
quarks. We also compare the results with the asymmetry predicted by QCD, and
show that its highest statistical significance is achieved with data samples of
top-antitop quark pairs of low invariant masses.Comment: 20 page
Human Dynamics: The Correspondence Patterns of Darwin and Einstein
While living in different historical era, Charles Darwin (1809-1882) and
Albert Einstein (1879-1955) were both prolific correspondents: Darwin sent
(received) at least 7,591 (6,530) letters during his lifetime while Einstein
sent (received) over 14,500 (16,200). Before email scientists were part of an
extensive university of letters, the main venue for exchanging new ideas and
results. But were the communication patterns of the pre-email times any
different from the current era of instant access? Here we show that while the
means have changed, the communication dynamics has not: Darwin's and Einstein's
pattern of correspondence and today's electronic exchanges follow the same
scaling laws. Their communication belongs, however, to a different universality
class from email communication, providing evidence for a new class of phenomena
capturing human dynamics.Comment: Supplementary Information available at http://www.nd.edu/~network
Quantum simulation of an extra dimension
We present a general strategy to simulate a D+1-dimensional quantum system
using a D-dimensional one. We analyze in detail a feasible implementation of
our scheme using optical lattice technology. The simplest non-trivial
realization of a fourth dimension corresponds to the creation of a bivolume
geometry. We also propose single- and many-particle experimental signatures to
detect the effects of the extra dimension.Comment: 5 pages, 3 figures, revtex style;v2 minor changes, references adde
Fractal extra dimension in Kaluza-Klein theory
Kaluza-Klein theory in which the geometry of an additional dimension is
fractal has been considered. In such a theory the mass of an elementary
electric charge appears to be many orders of magnitude smaller than the Planck
mass, and the "tower" of masses which correspond to higher integer charges
becomes aperiodic.Comment: 3 pages, accepted for publication in Phys.Rev.D (submitted on
3.28.2001
Extra Dimensions and Neutrinoless Double Beta Decay Experiments
The neutrinoless double beta decay is one of the few phenomena, belonging to
the non-standard physics, which is extensively being sought for in experiments.
In the present paper the link between the half-life of the neutrinoless double
beta decay and theories with large extra dimensions is explored. The use of the
sensitivities of currently planned experiments: DAMA, CANDLES,
COBRA, DCBA, CAMEO, GENIUS, GEM, MAJORANA, MOON, CUORE, EXO, and XMASS, gives
the possibility for a non-direct `experimental' verification of various extra
dimensional scenarios. We discuss also the results of the Heidelberg--Moscow
Collaboration. The calculations are based on the Majorana neutrino mass
generation mechanism in the Arkani-Hamed--Dimopoulos--Dvali model.Comment: I've decided to move the collection of my papers to arXiv for easier
acces
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