119180568
Effective gravitational equations for $f(R)$ braneworld models
Instituto de Fisica Universidade Federal Fluminense, Avenue Gal. Milton Tavares de Souza, s/n, CEP 24210-346 Niteroi-Rio de Janeiro
117828168
Possible Generalizations within Braneworld Scenarios: Torsion fields
In this Chapter we introduce the aspects in which torsion can influence the formalism of braneworld scenarios in general, and also how it is possible to measure such kind of effects, namely, for instance, the blackstring transverse area corrections and variation of quasar luminosity due to those corrections. We analyze the projected effective Einstein equation in a 4-dimensional arbitrary manifold embedded in a 5-dimensional Riemann-Cartan manifold. The Israel-Darmois matching conditions are investigated, in the context where the torsion discontinuity is orthogonal to the brane. Unexpectedly, the presence of torsion terms in the connection does not modify such conditions whatsoever, despite of the modification in the extrinsic curvature and in the connection. Then, by imposing the Z2-symmetry, the Einstein equation obtained via Gauss-Codazzi formalism is extended, in order to now encompass the torsion terms. We also show that the factors involving contorsion change drastically the effective Einstein equation on the brane, as well as the effective cosmological constant. Also, we present gravitational aspects of braneworld models endowed with torsion terms both in the bulk and on the brane. In order to investigate a conceivable and measurable gravitational effect, arising genuinely from bulk torsion terms, we analyze the variation in the black hole area by the presence of torsion. Furthermore, we extend the well known results about consistency conditions in a framework that incorporates brane torsion terms. It is shown, in a rough estimate, that the resulting effects are generally suppressed by the internal space volume.
56078295
Towards a hybrid compactification with a scalar–tensor global cosmic string
We derive a solution of the gravitational equations which leads to a braneworld scenario in six dimensions, using a global cosmic string solution in a low energy effective string theory framework. The final spacetime is composed by one warped brane with topology and a power law warp factor, and one non-compact extra dimension transverse to the brane; by looking at the current experimental bounds, we find a range of parameters in which, if the on-brane dimension has an acceptable size, it does not solve the hierarchy problem. In another example, this problem is smoothed by means of the Brans–Dicke parameter.
119686824
Regular Bulk Solutions and Black Strings from Dynamical Braneworlds with Variable Tension
Regular black strings solutions associated to a dynamical Friedmann-Robertson-Walker braneworld are obtained as a particular case of a regular bulk metric, in the context of a variable brane tension. By analyzing the 5D Kretschmann invariants, we show that the variable brane tension is capable to remove bulk singularities, along some eras of the evolution of the Universe. In particular, the black string time-dependent profile in the bulk is analyzed in the context of the McVittie metric on an E\"otv\"os fluid braneworld, wherein the fluid dynamical brane tension depends on the brane temperature. The whole bulk is shown to be regular for a Universe dominated by non-relativistic matter or by relativistic matter/radiation, as the cosmological time elapses. In a particular case the associated black strings are shown to have finite extension along the extra dimension, what prominently modify the higher-dimensional physical singularities. For a Universe dominated by matter or radiation, we show that the brane singularities are removed along the extra dimension, as an effect of the variable brane tension, corresponding also to the vanishing of the black string horizon. In this case there is a regular solution in the bulk. We show further that no additional physical singularity is introduced in the bulk when the Universe is dominated by a cosmological constant.
119652642
Black holes in realistic branes: Black string-like objects?
Abstract A realistic model describing a black string-like object in an expanding Universe is analyzed in the context of the McVittieʼs solution of the Einstein field equations. The bulk metric near the brane is provided analogously to previous solutions for black strings. In particular, we show that at least when the Hubble parameter on the brane is positive, a black string-like object seems to play a fundamental role in the braneworld scenario, generalizing the standard black strings in the context of a dynamical brane.
118609176
Static domain wall in braneworld gravity
In this paper we consider a static domain wall inside a 3-brane. Different from the standard achievement obtained in General Relativity, the analysis performed here gives a consistency condition for the existence of static domain walls in a braneworld gravitational scenario. Also the behavior of the domain wall’s gravitational field in the newtonian limit is shown.
15038787
New CP-violating parameters in cascade decays
We consider decay chains of the type $\stackrel{\ensuremath{\rightarrow}}{P}M+\ensuremath{\cdot}\ensuremath{\cdot}\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\cdot}}f+\ensuremath{\cdot}\ensuremath{\cdot}\ensuremath{\cdot},$ where M is a neutral meson that may mix with its antiparticle $\overline{M},$ before decaying into the final state f. Here P may be either a heavier neutral meson or a charged meson. We perform a rephasing-invariant analysis of the quantities that show up in such cascade decays. If the decay $\stackrel{\ensuremath{\rightarrow}}{P}M+\ensuremath{\cdot}\ensuremath{\cdot}\ensuremath{\cdot}$ (or the decay $\stackrel{\ensuremath{\rightarrow}}{P}\overline{M}+\ensuremath{\cdot}\ensuremath{\cdot}\ensuremath{\cdot})$ is forbidden, we find the usual ${\ensuremath{\lambda}}_{f}$ parameters describing the interference between the mixing of a neutral meson system and the decay from that system into the final state f. However, when both the $\stackrel{\ensuremath{\rightarrow}}{P}M+\ensuremath{\cdot}\ensuremath{\cdot}\ensuremath{\cdot}$ and $\stackrel{\ensuremath{\rightarrow}}{P}\overline{M}+\ensuremath{\cdot}\ensuremath{\cdot}\ensuremath{\cdot}$ decays are allowed, we find a new class of rephasing-invariant parameters, ${\ensuremath{\xi}}_{i},$ which measure the interference between the mixing of a neutral meson system and the decay from the initial state into that system. We show that the quantities ${\ensuremath{\lambda}}_{f}$ and ${\ensuremath{\xi}}_{i}$ are necessary and sufficient to describe all the interference effects present in the most general cascade decay. We discuss the various cascade decays in turn, highlighting the special features of each one.
118526359
Abelian symmetries in the two-Higgs-doublet model with fermions
We classify all possible implementations of an abelian symmetry in the two-Higgs-doublet model with fermions. We identify those symmetries which are consistent with non-vanishing quark masses and a CKM matrix which is not block-diagonal. Our analysis takes us from a plethora of possibilities down to 246 relevant cases, requiring only 34 distinct matrix forms. We show that applying Z_n with n \geq 4 to the scalar sector leads to a continuous U(1) symmetry in the whole Lagrangian. Finally, we address the possibilities of spontaneous CP violation and of natural suppression of the flavour changing neutral currents. We explain why our work is relevant even for non-abelian symmetries.
122214245
A two-Higgs doublet model with remarkable CP properties
We analyze generalized CP symmetries of two-Higgs doublet models, extending them from the scalar to the fermion sector of the theory. We show that, other than the usual CP transformation, there is only one of those symmetries which does not imply massless charged fermions. That single model which accommodates a fermionic mass spectrum compatible with experimental data possesses a remarkable feature. Through a soft breaking of the symmetry it displays a new type of spontaneous CP violation, which does not occur in the scalar sector responsible for the symmetry breaking mechanism but, rather, in the fermion sector.
119205906
Discrete and continuous symmetries in multi-Higgs-doublet models
We consider the Higgs sector of multi-Higgs-doublet models in the presence of simple symmetries relating the various fields. We construct basis-invariant observables which may in principle be used to detect these symmetries for any number of doublets. A categorization of the symmetries into classes is required, which we perform in detail for the case of two and three Higgs doublets.
55840509
The 125 GeV Higgs in the NMSSM in light of LHC results and astrophysics constraints
Daniel Albornoz Vásquez,1 Geneviève Bélanger,2 Céline Bœhm,3, 2 Jonathan Da Silva,2, 3 Peter Richardson,3 and Chris Wymant3 1Institut d’Astrophysique de Paris, UMR 7095 CNRS, Université Pierre et Marie Curie, 98 bis Boulevard Arago, Paris 75014, France 2LAPTH, U. de Savoie, CNRS, BP 110, 74941 Annecy-Le-Vieux, France. 3Institute for Particle Physics Phenomenology, University of Durham, Durham, DH1 3LE, UK