2,214 research outputs found

### Finite number of Kaluza-Klein modes, all with zero masses

Kaluza-Klein modes of fermions in a 5-dimensional toy model are considered.
The number of Kaluza-Klein modes that survive after integration over extra
dimensions is finite in this space. Moreover the extra dimensional piece of the
kinetic term induces no mass for the higher Kaluza-Klein modes on contrary to
the standard lore.Comment: Presentation is improved and typos are corrected, two appendices and
some references are added. No change in the essential content of the paper.
11 page

### Warped Kaluza-Klein Towers Revisited

Inspired by the warped Randall Sundrum scenario proposed to solve the mass
scale hierarchy problem with a compactified fifth extra dimension, a similar
model with no metric singularities has been elaborated. In this framework, the
Kaluza-Klein reduction equations for a real massless scalar field propagating
in the bulk have been studied carefully from the point of view of hermiticity
so as to formulate in a mathematically rigorous way all the possible boundary
conditions and corresponding mass eigenvalue towers and tachyon states. The
physical masses as observable in our four-dimensional brane are deduced from
these mass eigenvalues depending on the location of the brane on the extra
dimension axis. Examples of mass towers and tachyons and related field
probability densities are presented from numerical computations performed for
some arbitrary choices of the parameters of the model.Comment: 34 pages, 5 figure

### Threshold production of meta-stable bound states of Kaluza Klein excitations in Universal Extra Dimensions

We study the formation and detection at the next linear e^+e^- collider of
bound states of level-1 quark Kaluza-Klein excitations B_KK within a scenario
of universal extra-dimensions (UED). The interactions of such Kaluza-Klein
excitations are modeled by an alpha_s driven Coulomb potential. In order to
obtain the threshold cross-section, we employ the Green function method which
is known to properly describe the peaks below threshold and to yield a net
increase in the continuum region (above threshold) relative to the naive Born
cross-section. We study such effect at different values of the scale (R^-1) of
the extra-dimensions with an explicit calculation of the mass spectrum as given
by radiative corrections. The overall effect is roughly 2.7 at R^-1=300 GeV and
goes down to 2.2 at R^-1=1000 GeV and a relatively large number of events is
expected from N_events ~ 2.5*10^4 at R^-1=300 GeV down to N_events ~ 10^3 at
R^-1=1000 GeV at the anticipated annual integrated luminosity of L_0= 100
fb^-1. We finally discuss some potentially observable signatures such as the
multilepton channels 2j + 2l + missing energy, and 2j + 4l + missing energy for
which we estimate statistical significance >~ 2 for R^-1 up to 600 ~ 700 GeV.Comment: Accepted for publication in Phys. Rev. D. Enhanced version. 13 pages,
5 figures, 2 table

### Tests for Cosmological Evolution of a Brane Universe Model

The relativistic Friedmann Lemaitre cosmology model (FLCM) is very sucessful
to describe the evolution history of the Universe from the " First three
Minutes". Any alternative model should be consistent with the FLCM explanations
to the later stage evolutions of the Universe at certain points. An noncompact
extra dimension model was recently proposed by Randall and Sundrum. Binetruy et
al. obtained the modified Friedmann equation, in which the energy density of
the brane appears quadratically in contrast with the linear behavior of the
standard Friedmann equation. We investigate kinds of classical cosmological
effects of the new models and get a general solution of the cosmic evolution
for this extended model, with more detail discussions of the brane tension
parameter on these cosmological tests.Comment: 12 pages, 5 figures, to appear in IJMP

### A Classical Solution in Six-dimensional Gauge Theory with Higher Derivative Coupling

We show that the spin connection of the standard metric on a six-dimensional
sphere gives an exact solution to the generalized self-dual equations suggested
by Tchrakian some years ago. We work on an SO(6) gauge theory with a
higher-derivative coupling term. The model consists of vector fields only. The
pseudo-energy is bound from below by a topological charge which is proportional
to the winding number of spatial S^5 around the internal space SO(6). The fifth
homotopy group of SO(6) is, indeed, Z. The coupling constant of higher
derivative term is quadratic in the radius of the underlying space S^6.Comment: 7 pages, comments and a reference added, typos correcte

### Surface Geometry of 5D Black Holes and Black Rings

We discuss geometrical properties of the horizon surface of five-dimensional
rotating black holes and black rings. Geometrical invariants characterizing
these 3D geometries are calculated. We obtain a global embedding of the 5D
rotating black horizon surface into a flat space. We also describe the
Kaluza-Klein reduction of the black ring solution (along the direction of its
rotation) which relates this solution to the 4D metric of a static black hole
distorted by the presence of external scalar (dilaton) and vector
(`electromagnetic') field. The properties of the reduced black hole horizon and
its embedding in \E^3 are briefly discussed.Comment: 10 pages, 9 figures, Revtex

### Non Abelian gauge symmetries induced by the unobservability of extra-dimensions in a Kaluza-Klein approach

In this work we deal with the extension of the Kaluza-Klein approach to a
non-Abelian gauge theory; we show how we need to consider the link between the
n-dimensional model and a four-dimensional observer physics, in order to
reproduce fields equations and gauge transformations in the four-dimensional
picture. More precisely, in fields equations any dependence on
extra-coordinates is canceled out by an integration, as consequence of the
unobservability of extra-dimensions. Thus, by virtue of this extra-dimensions
unobservability, we are able to recast the multidimensional Einstein equations
into the four-dimensional Einstein-Yang-Mills ones, as well as all the right
gauge transformations of fields are induced. The same analysis is performed for
the Dirac equation describing the dynamics of the matter fields and, again, the
gauge coupling with Yang-Mills fields are inferred from the multidimensional
free fields theory, together with the proper spinors transformations.Comment: 5 pages, no figures, to appear in Mod. Phys. Lett.

### 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.

### Gravitation interaction with extra dimension and periodic structure of the hadron scattering amplitude

The behavior of the hadron scattering amplitude determined by the gravitation
interaction of hadron at high energies with impact of the KK-modes in d-brane
models of gravity is examined. The possible periodic structure of the
scattering amplitude and its dependence on the number of additional dimensions
are analyzed. The effects of the gravitational hadron form factors obtained
from the hadron eneralized parton distributions (GPDs) on the behavior of the
interaction potential and the scattering amplitude are analyzed. It is shown
that in most part the periodic structure comes from the approximation of our
calculations.Comment: 9 pages, 8 figures, talk on the Intern. Workshop "Bogoliubov
Readings", Dubna (2010); updated reference

### 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

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