Control of quantum fluctuations for a Yukawa interaction in the Kaluza Klein picture

We study a system of fermions interacting with a scalar field, in 4+1 dimensions where the 5th dimension is compactified, using an exact functional method, where quantum fluctuations are controlled by the amplitude of the bare fermion mass. The integration of our equationsleads to the properties of the dressed Yukawa coupling, that we study at one-loop so as to show the consistency of the approach. Beyond one loop, the non-perturbative aspect of the method gives us the possibility to derive the dynamical fermion mass. The result obtained is cut off independent and this derivation proposes an alternative to the Schwinger-Dyson approach.Comment: extended discussion on the scalar effective potentia

Cosmology and Fermion Confinement in a Scalar-Field-Generated Domain Wall Brane in Five Dimensions

We consider a brane generated by a scalar field domain wall configuration in 4+1 dimensions, interpolating, in most cases, between two vacua of the field. We study the cosmology of such a system in the cases where the effective four-dimensional brane metric is de Sitter or anti de Sitter, including a discussion of the bulk coordinate singularities present in the de-Sitter case. We demonstrate that a scalar field kink configuration can support a brane with dS$_4$ cosmology, despite the presence of coordinate singularities in the metric. We examine the trapping of fermion fields on the domain wall for nontrivial brane cosmology.Comment: 29 pages, 12 figures; minor changes, accepted by JHE

Branon search in hadronic colliders

In the context of the brane-world scenarios with compactified extra dimensions, we study the production of brane fluctuations (branons) in hadron colliders ($p \bar p$, $pp$ and $e^\pm p$) in terms of the brane tension parameter $f$, the branon mass $M$ and the number of branons $N$. From the absence of monojets events at HERA and Tevatron (run I), we set bounds on these parameters and we also study how such bounds could be improved at Tevatron (run II) and the future LHC. The single photon channel is also analyzed for the two last colliders.Comment: 17 pages, 10 figures, LaTeX. New comments and figures included. Final version to appear in Phys. Rev.

Running Coupling with Minimal Length

In models with large additional dimensions, the GUT scale can be lowered to values accessible by future colliders. Due to modification of the loop corrections from particles propagating into the extra dimensions, the logarithmic running of the couplings of the Standard Model is turned into a power law. These loop-correction are divergent and the standard way to achieve finiteness is the introduction of a cut-off. The question remains, whether the results are reliable as they depend on an unphysical parameter. In this paper, we show that this running of the coupling can be calculated within a model including the existence of a minimal length scale. The minimal length acts as a natural regulator and allows us to confirm cut-off computations.Comment: 26 pages, 5 figures, typos corrected, replaced with published versio

A Gravitational Potential with Extra-dimensions and Spin Effects In Hadronic Reactions

The impact of the KK-modes in d-brane models of gravity with large compactification radii and TeV-scale quantum gravity on the hadronic potential at small impact parameters is examined. The effects of the gravitational hadronic form factors obtained from the generalized parton distributions (GPDs) on the behavior of the gravitational potential and the possible spin correlation effects are also analysed.Comment: 13 pages, 7 figure

Seed perturbations for primordial magnetic fields from MSSM flat directions

We demonstrate that the MSSM flat directions can naturally account for the seed magnetic fields in the early Universe. The non-zero vacuum expectation value of an MSSM flat direction condensate provides masses to the gauge fields and thereby breaks conformal invariance. During inflation the condensate receives spatial perturbations and $SU(2) x U(1)_Y$ gauge currents are generated together with (hyper)magnetic fields. When these long wavelength vector perturbations reenter our horizon they give rise to $U(1)_{em}$ magnetic fields with an amplitude of $10^{-30}$ Gauss, as required by the dynamo mechanism.Comment: 4 pages, RevTeX

Non-Gaussianity from Instant and Tachyonic Preheating

We study non-Gaussianity in two distinct models of preheating: instant and tachyonic. In instant preheating non-Gaussianity is sourced by the local terms generated through the coupled perturbations of the two scalar fields. We find that the non-Gaussianity parameter is given by $f_{NL}^{\phi}\sim 2g < O(1)$, where $g$ is a coupling constant, so that instant preheating is unlikely to be constrained by WMAP or Planck. In the case of tachyonic preheating non-Gaussianity arises solely from the instability of the tachyon matter and is found to be large. We find that for single field inflation the present WMAP data implies a bound $V_{0}^{1/4}/M_{P}\leq 10^{-4}$ on the scale of tachyonic instability. We argue that the tachyonic preheating limits are useful also for string-motivated inflationary models.Comment: 12 pages, 1 figure, additional discussion, improved constraint on the scale of tachyonic preheatin

Neutrino mass, proton decay and dark matter in TeV scale universal extra dimension models

We show how the problem of small neutrino masses and suppressed proton decay can be simultaneously resolved in 6-D universal extra dimension models (UED) with a low fundamental scale using extended gauge groups that contain the local $B-L$ symmetry. The extra space dimensions are compactified either on a $T^2/Z_2$ or $T^2/Z_2\times Z'_2$ orbifold depending on whether the full gauge group is $SU(2)_L\times U(1)_{I_{3R}}\times U(1)_{B-L}$ or $SU(2)_L\times SU(2)_{R}\times U(1)_{B-L}$. In both cases, neutrino masses are suppressed by an appropriate orbifold parity assignment for the standard model singlet neutrinos and the proton decay rate is suppressed due to a residual discrete symmetry left over from compactification. For lower values of the fundamental scale, a dominant decay mode of the neutron is $n\to 3 \nu$. An interesting consequence of the model is a possible two component picture for dark matter of the universe.Comment: 25 pages, two minor typos correcte