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