arXiv subjects

B. de Carlos

Publications and source records attributed to B. de Carlos.

At least 19 recordsLinked to original sources

arXiv2008

Moduli evolution in the presence of thermal corrections

We study the effect of thermal corrections on the evolution of moduli in effective Supergravity models. This is motivated by previous results in the literature suggesting that these corrections could alter and, even, erase the presence of a minimum in the zero temperature potential, something that would have disastrous consequences in these particular models. We show that, in a representative sample of flux compactification constructions, this need not be the case, although we find that the inclusion of thermal corrections can dramatically decrease the region of initial conditions for which the moduli are stabilised. Moreover, the bounds on the reheating temperature coming from demanding that the full, finite temperature potential, has a minimum can be considerably relaxed given the slow pace at which the evolution proceeds.

hep-ph↗

arXiv2007

Inflation in uplifted Supergravities

We present a model of slow-roll inflation in the context of effective Supergravities arising from string theories. The uplifting of the potential (to generate dS or Minkowski vacua) is provided by the D-term associated to an anomalous U(1), in a fully consistent and gauge invariant formulation. We develop a minimal working model which incorporates eternal topological inflation and complies with observational constraints, avoiding the usual obstacles to implement successful inflation ("eta problem" and initial condition problem among others).

hep-th↗

arXiv2006

deSitter vacua from uplifting D-terms in effective supergravities from realistic strings

We study the possibility of using the D-term associated to an anomalous U(1) for the uplifting of AdS vacua (to dS or Minkowski vacua) in effective supergravities arising from string theories, particularly in the type IIB context put forward by Kachru, Kallosh, Linde and Trivedi (KKLT). We find a gauge invariant formulation of such a scenario (avoiding previous inconsistencies), where the anomalous D-term cannot be cancelled, thus triggering the uplifting of the vacua. Then, we examine the general conditions for this to happen. Finally, we illustrate the results by presenting different successful examples in the type IIB context.

hep-th↗

arXiv2005

Moduli evolution in the presence of flux compactifications

We study the cosmological evolution of the volume moduli in a class of recently proposed Inflationary Universe models arising out of Type IIB string theory, where a number of the moduli fields have been stabilised through flux compactifications. Developing an approach initially introduced in [3] we show, in agreement with [4], how the presence of extra sources of matter act so as to provide additional friction, slowing the modulus field as it evolves down its potential, thereby vastly increasing the region of parameter space which leads to the eventual stabilisation of these fields. Extending the case to include both the real and imaginary parts of the volume modulus, we show how the parameter space of inital conditions is modified and comment on the impact for these inflationary models arising out of flux type compactifications.

hep-ph↗

arXiv2004

Moving Five-Branes and Membrane Instantons in Low Energy Heterotic M-Theory

We study cosmological solutions in the context of 4-dimensional low energy Heterotic M-theory with moving bulk branes. In particular we present non-trivial, analytic axion solutions generated by new symmetries of the full potential-free action which are similar to 'triple axion' solutions found in Pre-Big-Bang (PBB) cosmologies. We also consider the presence of a non-perturbative superpotential, for which we find cosmological solutions with and without a background perfect fluid. In the absence of a fluid the dilaton and the T-modulus go to the potential-free solutions at late time, while the moving brane tries to avoid colliding with the boundary and stabilize within the bulk. When the fluid is included, we find that the real parts of the fields track its behaviour and that the moving brane gets stabilized at the middle point between the boundaries. In this latter case we can make analytic approximations for the evolution of the fields whether or not axions are included and we consider the possibility of this set up being a realization of the quintessential scenario.

hep-th↗

arXiv2004

Regular compactifications and Higgs model vortices

We present full numerical solutions to the system of a global string embedded in a six-dimensional space time. The solutions are regular everywhere and do confine gravity in our four-dimensional world. They depend on the value of the (negative) cosmological constant in the bulk and on the parameters of the Higgs potential, and we perform a systematic study to determine their allowed values. We also comment on the relation of our results with previous studies on the same subject and on their phenomenological viability.

hep-th↗

arXiv2003

A cigar-like Universe

We study the localization of gravity on a string-like topological defect within a 6-dimensional space-time. Assuming zero cosmological constant we find complete numerical solutions to a set of first-order, Bogomol'nyi-Prasad-Sommeferld (BPS)-like, equations for the metric and the scalar field, where the dynamics of the latter are dictated by a supergravity-type potential. Our axially symmetric solutions have no deficit angle and factorize as $AdS_5 \times S_1 $ far from the core. They are regular everywhere, providing complete smooth cigar-like geometries. The total energy of these configurations depends only on the boundary conditions for the warp factor and it is shown to vanish.

hep-th↗

arXiv2001

BPS Domain Walls in super Yang-Mills and Landau-Ginzburg models

We study domain walls in two different extensions of super Yang--Mills characterized by the absence of a logarithmic term in their effective superpotential. The models, defined by the usual gaugino condensate and an extra field Y, give different patterns of domain walls despite both leading to the same effective limit for heavy Y, i.e. the Veneziano--Yankielowicz effective Lagrangian of super Yang--Mills. We explain the origin of those differences and also give a physical motivation for introducing the field Y.

hep-th↗

arXiv2001

Domain Walls in Supersymmetric QCD

In this talk we construct BPS-saturated domain walls in supersymmetric QCD, for any values of the masses of the chiral matter superfields. We compare our results to those already obtained in the literature and we also discuss their range of applicability, as well as future directions that would be desirable to explore in order to achieve a complete understanding of supersymmetric gluodynamics as a step in improving our knowledge of how QCD works.

hep-th↗

arXiv2001

Moduli Evolution in Heterotic Scenarios

We discuss several aspects of the cosmological evolution of moduli fields in heterotic string/M-theory scenarios. In particular we study the equations of motion of both the dilaton and overall modulus of these theories in the presence of an expanding Universe and under different assumptions. First we analyse the impact of their couplings to matter fields, which turns out to be negligible in the string and M-theory scenarios. Then we examine in detail the possibility of scaling in M-theory, i.e. how the moduli would evolve naturally to their minima instead of rolling past them in the presence of a dominating background. In this case we find interesting and positive results, and we compare them to the analogous situation in the heterotic string.

hep-ph↗

arXiv2000

Moduli as Inflatons in Heterotic M-theory

We consider different cosmological aspects of Heterotic M-theory. In particular we look at the dynamical behaviour of the two relevant moduli in the theory, namely the length of the eleventh segment (pi rho) and the volume of the internal six manifold (V) in models where supersymmetry is broken by multiple gaugino condensation. We look at different ways to stabilise these moduli, namely racetrack scenarios with or without non-perturbative corrections to the Kahler potential. The existence of different flat directions in the scalar potential, and the way in which they can be partially lifted, is discussed as well as their possible role in constructing a viable model of inflation. Some other implications such as the status of the moduli problem within these models are also studied.

hep-ph↗

arXiv2000

Cosmological Aspects of Heterotic M-theory

In this talk we discuss a few relevant aspects of heterotic M-theory. These are the stabilization of the two relevant moduli (the length of the eleventh segment (pi rho) and the volume of the internal six manifold (V)) in models where supersymmetry is broken by multiple gaugino condensation and non-perturbative corrections to the Kahler potential; the existence of almost flat directions in the scalar potential; the possibility of lifting them, and their role in constructing a viable model of inflation. Finally, we review the status of the moduli problem within these models. T

hep-ph↗

arXiv1999

Domain walls in supersymmetric QCD

We consider domain walls that appear in supersymmetric SU(N) with one massive flavour. In particular, for N > 3 we explicitly construct the elementary domain wall that interpolates between two contiguous vacua. We show that these solutions are BPS saturated for any value of the mass of the matter fields. We also comment on their large N limit and their relevance for supersymmetric gluodynamics.

hep-th↗

arXiv1999

Domain walls in supersymmetric QCD: from weak to strong coupling

We consider domain walls that appear in supersymmetric QCD with Nf < Nc massive flavours. In particular, for 2 Nf < Nc we explicitly construct the domain walls that interpolate between vacua labeled by i and (i+ N_f). We show that these solutions are Bogomol'nyi-Prasad-Sommerfield (BPS) saturated for any value of the mass of the matter fields. This fact allows us to evaluate the large mass limit of these domain walls. We comment on the relevance of these solutions for supersymmetric gluodynamics.

hep-th↗

arXiv1998

Anomalous U(1), gaugino condensation and supergravity

The interplay between gaugino condensation and an anomalous Fayet-Iliopoulos term in string theories is not trivial and has important consequences concerning the size and type of the soft SUSY breaking terms. In this paper we examine this issue, generalizing previous work to the supergravity context. This allows, in particular, to properly implement the cancellation of the cosmological constant, which is crucial for a correct treatment of the soft breaking terms. We obtain that the D-term contribution to the soft masses is expected to be larger than the F-term one. Moreover gaugino masses must be much smaller than scalar masses. We illustrate these results with explicit examples. All this has relevant phenomenological consequences, amending previous results in the literature.

hep-ph↗

arXiv1998

Stabilizing the Dilaton in Superstring Cosmology

We address the important issue of stabilizing the dilaton in the context of superstring cosmology. Scalar potentials which arise out of gaugino condensates in string models are generally exponential in nature. In a cosmological setting this allows for the existence of quasi scaling solutions, in which the energy density of the scalar field can, for a period, become a fixed fraction of the background density, due to the friction of the background expansion. Eventually the field can be trapped in the minimum of its potential as it leaves the scaling regime. We investigate this possibility in various gaugino condensation models and show that stable solutions for the dilaton are far more common than one would have naively thought.

hep-th↗

arXiv1997

On non-perturbative corrections to the Kahler potential

We present the results of a detailed investigation into the consequences of adding specific string motivated non-perturbative corrections to the usual tree level Kahler potential in dilaton dominated scenarios. The success of the model is judged through our ability to obtain a realistic VEV for the dilaton < Re S > ~ 2, corresponding to the true minima of the scalar potential and being associated with a reasonable value for the SUSY breaking scale via the gravitino mass. The status of the so-called moduli problem is also reviewed in each of the ansatze studied. Those include previous proposals made in the context of both the chiral and the linear multiplet formalisms to describe gaugino condensation, and a new ansatz which shows explicitly the equivalence between the two.

hep-ph↗

arXiv1997

Weak Magnetic Dipole Moments in the MSSM

We calculate the weak magnetic dipole moment of different fermions in the MSSM. In particular, we consider in detail the predictions for the WMDM of the tau lepton and bottom quark. We compare the purely SUSY contributions with two Higss doublet models and SM predictions. For the tau lepton, we show that chargino diagrams give the main SUSY contribution, which for tan beta=50 can be one order of magnitude bigger than the SM prediction. For the b quark, gluino diagrams provide the main SUSY contribution to its weak anomalous dipole moment, which is still dominated by gluon contributions. We also study how the universality assumption in the slepton sector induces correlations between the SUSY contributions to the tau WMDM and to (g-2) of the muon.

hep-ph↗