37823775
Brane cosmic string compactification in Brans-Dicke theory
We investigate an alternative compactification of extra dimensions using local cosmic string in the Brans-Dicke gravity framework. In the context of dynamical systems it is possible to show that there exist a stable field configuration for the Einstein-Brans-Dicke equations. We explore the analogies between this particular model and the Randall-Sundrum scenario.
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.
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.
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.
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.
8371193
Measurements of new physics in B -> pi pi decays
If new physics (NP) is present in B -> pi pi decays, it can affect the isospin I=2 or I=0 channels. In this paper, we discuss various methods for detecting and measuring this NP. The techniques have increasing amounts of theoretical hadronic input. If NP is eventually detected in B -> pi pi -- there is no evidence for it at present -- one will be able to distinguish I=2 and I=0, and measure its parameters, using these methods.
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.
31481331
Stability of the normal vacuum in multi-Higgs-doublet models
We show that the vacuum structure of a generic multi-Higgs-doublet model shares several important features with the vacuum structure of the two and three Higgs-doublet model. In particular, one can still define the usual charge breaking, spontaneous $CP$ breaking, and normal (charge and $CP$ preserving) stationary points. We analyze the possibility of charge or spontaneous $CP$ breaking by studying the relative depth of the potential in each of the possible stationary points.
10678678
Decoupling or nondecoupling: Is that the R($b$) question?
The top quark is well known for the nondecoupling effects it implies in ρ and Rb. The recent experimental Rb data exhibits a disagreement with the SM prediction at more than the 3σ level. It is tempting to explore whether this might be due to nondecoupling New Physics effects, opposite to those of the top. We investigate this issue in the context of models with an extra family of right or left handed, singlet or doublet quarks. It is shown that, contrary to what
120761568
Approximate flavor symmetries in the lepton sector
Approximate flavor symmetries in the quark sector have been used as a handle on physics beyond the standard model. Because of the great interest in neutrino masses and mixings and the wealth of existing and proposed neutrino experiments it is important to extend this analysis to the leptonic sector. We show that in the seesaw mechanism the neutrino masses and mixing angles do not depend on the details of the right-handed neutrino flavor symmetry breaking, and are related by a simple formula. We propose several [ital Ansa]$[ital uml]---[ital tze] which relate different flavor symmetry-breaking parameters and find that the MSW solution to the solar neutrino problem is always easily fit. Further, the [nu][sub [mu]-][nu][sub [tau]] oscillation is unlikely to solve the atmospheric neutrino problem and, if we fix the neutrino mass scale by the MSW solution, the neutrino masses are found to be too small to close the Universe.