The Nature of Dark Energy from deep Cluster Abundance

We show that using the redshift dependence of the deep cluster abundance to detect the nature of Dark Energy is a serious challenge. We compare the expected differences between flat LCDM models, with different Omega_mo, with the difference between LCDM and dynamical DE models. In the former case, cluster abundances in comoving volume and geometrical factors act in the same direction, yielding a significant difference between the expected angular densities. On the contrary, when we keep a constant Omega_mo and change the DE nature,abundances in comoving volume and geometrical factors act in the opposite direction, so that the expected differences in angular densities reduce to small factors

Algebraic Aspects of the Background Field Method

We discuss some algebraic properties of the background field method. We introduce an extra gauge-fixing term for the background gauge field right at the beginning in the action in such a way that BRST invariance is preserved. The background effective action is considered and it is shown to satisfy both the Slavnov-Taylor identities and the Ward identities. This allows to prove the background equivalence theorem by means of the standard techniques. We show that the Legendre transform W_{bg} of the background gauge invariant action gives the same physical amplitudes as the original one we started with. Moreover, we point out that W_{bg} cannot in general be derived from a classical action by the Gell-Mann-Low formula. Finally, we show that the BRST doublet generated from the background field does not modify the anomaly of the original underlying gauge theory. The proof is algebraic and makes no use of arguments based on power-counting

Limits on coupling between dark components

DM--DE coupling can be a phenomenological indication of a common origin of the dark cosmic components. In this work we outline a new constraint to coupled--DE models: the coupling can partially or totally suppress the Meszaros effect, yielding transfered spectra with quite a soft bending above $k_{hor,eq}$. Models affected by this anomaly do not show major variation in the CMB anisotropy spectrum and it is herefore hard to reconcile them with both CMB and deep sample data, through the same value of the primeval spectral index

Supersymmetric black holes and attractors in gauged supergravity with hypermultiplets

We consider four-dimensional N = 2 supergravity coupled to vector- and hypermultiplets, where abelian isometries of the quaternionic Kähler hypermultiplet scalar manifold are gauged. Using the recipe given by Meessen and Ortín in arXiv:1204.0493, we analytically construct a supersymmetric black hole solution for the case of just one vector multiplet with prepotential ℱ = − i χ 0 χ 1 $$\mathrm{\mathcal{F}}=-i{\chi}^0{\chi}^1$$ , and the universal hypermultiplet. This solution has a running dilaton, and it interpolates between AdS 2 × H 2 at the horizon and a hyperscaling-violating type geometry at infinity, conformal to AdS 2 × H 2 . It carries two magnetic charges that are completely fixed in terms of the parameters that appear in the Killing vector used for the gauging

Challenges in Double Beta Decay

In the past ten years, neutrino oscillation experiments have provided the incontrovertible evidence that neutrinos mix and have finite masses. These results represent the strongest demonstration that the electroweak Standard Model is incomplete and that new Physics beyond it must exist. In this scenario, a unique role is played by the Neutrinoless Double Beta Decay searches which can probe lepton number conservation and investigate the Dirac/Majorana nature of the neutrinos and their absolute mass scale (hierarchy problem) with unprecedented sensitivity. Today Neutrinoless Double Beta Decay faces a new era where large-scale experiments with a sensitivity approaching the so-called degenerate-hierarchy region are nearly ready to start and where the challenge for the next future is the construction of detectors characterized by a tonne-scale size and an incredibly low background. A number of new proposed projects took up this challenge. These are based either on large expansions of the present experiments or on new ideas to improve the technical performance and/or reduce the background contributions. In this paper, a review of the most relevant ongoing experiments is given. The most relevant parameters contributing to the experimental sensitivity are discussed and a critical comparison of the future projects is proposed

AdS 4 compactifications of AdS 7 solutions in type II supergravity

We find new classes of AdS 4 solutions with localized branes and orientifolds, both analytic and numerical. We start with an Ansatz for the pure spinors inspired by a recently found class of AdS 7 × M 3 solutions in massive IIA; we replace the AdS 7 by AdS 4 × Σ 3 , and we fibre M 3 over Σ 3 in a way inspired by a field theory SU(2) twist. We are able to reduce the problem to a system of five ODEs; a further Ansatz reduces them to three. Their solutions can be bijectively mapped to the AdS 7 solutions via a simple universal map. This also allows to find a simple analytic form for these solutions. They are naturally interpreted as twisted compactifications of the (1, 0) CFT 6 ’s dual to the AdS 7 solutions. The larger system of five ODEs also admits more general numerical solutions, again with localized branes; regularity is achieved via an attractor mechanism

6d → 5d → 4d reduction of BPS attractors in flat gauged supergravities

Via a series of Kaluza–Klein (KK) and Scherk–Schwarz (SS) compactifications we relate BPS attractors and their complete (in general non-BPS) flows to a Minkowski vacuum in gauged supergravities with vanishing scalar potential in 4, 5, and 6 dimensions. This way we can look at a class of extremal non-BPS black holes and strings from IIB string theory viewpoint, keeping 4 supercharges on the horizon. Our results imply the existence of a dual 2d N=(0,2) superconformal field theory (SCFT) that originates from a parent N=(4,4) theory living on a D1–D5 system

Attractors, black objects and holographic RG flows in 5d maximal gauged supergravities

We perform a systematic search for static solutions in different sectors of 5d $\mathcal{N}$ = 8 supergravities with compact and non-compact gauged R-symmetry groups, finding new and listing already known backgrounds. Due to the variety of possible gauge groups and resulting scalar potentials, the maximally symmetric vacua we encounter in these theories can be Minkowski, de Sitter, or anti-de Sitter. There exist BPS and non-BPS near-horizon geometries and full solutions with all these three types of asymptotics, corresponding to black holes, branes, strings, rings, and other black objects with more exotic horizon topologies, supported by U(1) and SU(2) charges. The asymptotically AdS 5 solutions also have a clear holographic interpretation as RG flows of field theories on D3 branes, wrapped on compact 2- and 3-manifolds

Pure spinor equations to lift gauged supergravity

We rewrite the equations for ten-dimensional supersymmetry in a way formally identical to a necessary and sufficient G -structure system in $\mathcal{N}$  = 2 gauged supergravity, where all four-dimensional quantities are replaced by combinations of pure spinors and fluxes in the internal space. This provides a way to look for lifts of BPS solutions without having to reduce or even rewrite the ten-dimensional action. In particular this avoids the problem of consistent truncation, and the introduction of unphysical gravitino multiplets

The high-temperature expansions of the higher susceptibilities for the Ising model in general dimension d

The high-temperature expansion coefficients of the ordinary and the higher susceptibilities of the spin-1/2 nearest-neighbor Ising model are calculated exactly up to the 20th order for a general d-dimensional (hyper)-simple-cubical lattice. These series are analyzed to study the dependence of critical parameters on the lattice dimensionality. Using the general $d$ expression of the ordinary susceptibility, we have more than doubled the length of the existing series expansion of the critical temperature in powers of 1/d