Search

We examine cosmological inflation in a broad family of scalar-tensor models characterized by scalar-dependent non minimal kinetic couplings and Gauss-Bonnet terms. Using a slow roll-approximation, we compute in detail theoretical expectations of observables as spectral indexes, scalar-to-tensor ratio, their running and their running of the running in terms of the parameters which characterize the scalar-tensor model. Hierarchies of consistency equations relating scalar and tensor pertubations and higher order running parameters are presented and examined at the slow roll approximation for the kind of models of interest in this work. From We find detailed expressions for constraints among these parameters. For a specific model, we analyse such quantities and make contact with latest Planck observational data .

We study the shadow behaviors of five dimensional (5D) black holes embedded in type IIB superstring/supergravity inspired spacetimes by considering solutions with and without rotations. Geometrical properties as shapes and sizes are analyzed in terms of the D3-brane number and the rotation parameter. Concretely, we find that the shapes are indeed significantly distorted by such physical parameters and the size of the shadows decreases with the brane or "color" number and the rotation. Then, we investigate geometrical observables and energy emission rate aspects.

We study the shadows of four dimensional black holes in M-theory inspired models. We first inspect the influence of M2-branes on such optical aspects for non-rotating solutions. In particular, we show that the M2-brane number can control the circular shadow size. This geometrical behavior is distorted for rotating solutions exhibiting cardioid shapes in certain moduli space regions. Implementing a rotation parameter, we analyze the geometrical shadow deformations. Among others, we recover the circular behaviors for a large M2-brane number. Investigating the energy emission rate at high energies, we find, in a well-defined approximation, that the associated peak decreases with the M2-brane number. Moreover, we investigate a possible connection with observations (from Event Horizon Telescope or future devices) from a particular M-theory compactification by deriving certain constraints on the M2-brane number in the light of the $M87^\star$ observational parameters., Comment: latex, 21 pages, and 8 figures. A section in connexion with observations has been added. Accepted for publication in International Journal of Modern Physics D (2021)

We study $d$-dimensional $AdS$ black holes surrounded by Dark Energy (DE), embedded in $D$-dimensional M-theory/superstring inspired models having $AdS_d \times \mathbb{S}^{d+k}$ space-time with $D=2d+k$. We focus on the thermodynamic Hawking-Page phase transitions of quintessential DE black hole solutions, whose microscopical origin is linked to $N$ coincident $(d-2)$-branes supposed to live in such $(2d+k)$-dimensional models. Interpreting the cosmological constant as the number of colors $\propto N^{\frac{d-1}{2}}$, we calculate various thermodynamical quantities in terms of brane number, entropy and DE contributions. Computing the chemical potential conjugated to the number of colors in the absence of DE, we show that a generic black hole is more stable for a larger number of branes for lower dimensions $d$.In the presence of DE, we find that the DE state parameter $\omega_q$ should take particular values, for $(D,d,k)$ models, providing a non trivial phase transition structure.

Mass formulas for multicenter BPS 4D black holes are presented. For example, ADM mass for a two center BPS solution can be related to the intercencenter distance $r$, the angular momentum $J^2$, the dyonic charge vectors $q_i$ and the value of the scalar moduli at infinity ($z_\infty$)by $M_{ADM}^2 =A\left (1+ \alpha J^2\left(1+\frac{2M_{ADM}}{r}+\frac{A}{r^2}\right)\right)$ where $A(Q),\alpha(q_i)$ are symplectic invariant quantities ($Q$, the total charge vector) depending on the special geometry prepotential defining the theory. The formula predicts the existence of a continuos class, for fixed value of the charges, of BH's with interdistances $r\in (0,\infty)$ and $M_{ADM}\in (\infty,M_\infty)$. Smarr-like expressions incorporating the intercenter distance are obtained from it: $$ dM\equiv\Omega d J+\Phi_i d q_i+ F dr,$$ in addition to an effective angular velocity $\Omega$ and electromagnetic potentials $\Phi_i$, the equation allows to define an effective "force", $F$, acting between the centers. This effective force is always negative: at infinity we recover the familiar Newton law $F\sim 1/r^2$ while at short distances $F\sim f_0+f_1/r^2$. Similar results can be easily obtained for more general models and number of centers.

We study General Freudenthal Transformations (GFT) on black hole solutions in Einstein-Maxwell-Scalar (super)gravity theories with global symmetry of type $E_7$. GFT can be considered as a 2-parameter, $a, b\in {\mathbb R}$, generalisation of Freudenthal duality: $x\mapsto x_F= a x+b\tilde{x}$, where $x$ is the vector of the electromagnetic charges, an element of a Freudenthal triple system (FTS), carried by a large black hole and $ \tilde{x}$ is its Freudenthal dual. These transformations leave the Bekenstein-Hawking entropy invariant up to a scalar factor given by $a^2\pm b^2$. For any $x$ there exists a one parameter subset of GFT that leave the entropy invariant, $a^2\pm b^2=1$, defining the subgroup of Freudenthal rotations. The Freudenthal plane defined by span$_\mathbb{R}\{x, \tilde{x}\}$ is closed under GFT and is foliated by the orbits of the Freudenthal rotations. Having introduced the basic definitions and presented their properties in detail, we consider the relation of GFT to the global sysmmetries or U-dualites in the context of supergravity. We consider explicit examples in pure supergravity, axion-dilaton theories and $N=2,D=4$ supergravities obtained from $D=5$ by dimensional reductions associated to (non-degenerate) $ reduced$ FTS's descending from cubic Jordan Algebras., Comment: 65 pages

We present a detailed description of N=2 stationary BPS multicenter black hole solutions for quadratic prepotentials with an arbitrary number of centers and scalar fields making a systematic use of the algebraic properties of the matrix of second derivatives of the prepotential, $\mathcal{S}$, which in this case is a scalar-independent matrix. In particular we obtain bounds on the physical parameter of the multicenter solution such as horizon areas and ADM mass. We discuss the possibility and convenience of setting up a basis of the symplectic vector space built from charge eigenvectors of the $\ssigma$, the set of vectors $(\Ppm q_a)$ with $\Ppm$ $\ssigma$-eigenspace proyectors. The anti-involution matrix $\mathcal{S}$ can be understood as a Freudenthal duality $\tilde{x}=\ssigma x$. We show that this duality can be generalized to "Freudenthal transformations" $$x\to \lambda\exp(\theta \ssigma) x= a x+b\tilde{x}$$ under which the horizon area, ADM mass and intercenter distances scale up leaving constant the fix point scalars. In the special case $\lambda=1$, "$\ssigma$-rotations", the transformations leave invariant the solution. The standard Freudental duality can be written as $\tilde x= \exp(\pi/2 \ssigma) x .$ We argue that these generalized transformations leave also invariant the general stringy extremal quartic form $\Delta_4$, $\Delta_4(x)= \Delta_4(\cos\theta x+\sin\theta\tilde{x})$., Comment: Latex 27 pages (11pt). Some modifications introduced. Minor misprints corrected. References added

The discovery by the ATLAS and CMS experiments of a new boson with mass around 125 GeV and with measured properties compatible with those of a Standard-Model Higgs boson, coupled with the absence of discoveries of phenomena beyond the Standard Model at the TeV scale, has triggered interest in ideas for future Higgs factories. A new circular e+e- collider hosted in a 80 to 100 km tunnel, TLEP, is among the most attractive solutions proposed so far. It has a clean experimental environment, produces high luminosity for top-quark, Higgs boson, W and Z studies, accommodates multiple detectors, and can reach energies up to the t-tbar threshold and beyond. It will enable measurements of the Higgs boson properties and of Electroweak Symmetry-Breaking (EWSB) parameters with unequalled precision, offering exploration of physics beyond the Standard Model in the multi-TeV range. Moreover, being the natural precursor of the VHE-LHC, a 100 TeV hadron machine in the same tunnel, it builds up a long-term vision for particle physics. Altogether, the combination of TLEP and the VHE-LHC offers, for a great cost effectiveness, the best precision and the best search reach of all options presently on the market. This paper presents a first appraisal of the salient features of the TLEP physics potential, to serve as a baseline for a more extensive design study., Comment: 43 pages, 18 figures, 11 tables, 85 references. Changes with respect to version V2: The comments from the JHEP referee are now included

We construct the most general maximal gauged/massive supergravity in $d=9$ dimensions and determine its extended field content by using the embedding tensor method., Comment: XVIIth European workshop on String theory 2011, Padua, Italy, 4-9 september 2011

On the light of the recent LHC boson discovery, we present a phenomenological evaluation of the ratio $\rho_t=m_Z m_t/m_H^2$, from the LHC combined $m_H$ value, we get ($ (1\sigma)$) $$\rho_t^{(exp)}= 0.9956\pm 0.0081.$$ This value is close to one with a precision of the order $\sim 1\%$. Similarly we evaluate the ratio $\rho_{Wt}=(m_W + m_t)/(2 m_H)$. From the up-to-date mass values we get $\rho_{Wt}^{(exp)}= 1.0066\pm 0.0035\; (1\sigma).$ The Higgs mass is numerically close (at the $1\%$ level) to the $m_H\sim (m_W+m_t)/2$. From these relations we can write any two mass ratios as a function of, exclusively, the Weinberg angle (with a precision of the order of $1\%$ or better): \begin{eqnarray} \frac{m_i}{m_j}&\simeq & f_{ij}(\theta_W),\quad i,j=W,Z,H,t. \end{eqnarray} For example:$m_H/m_Z \simeq 1+\sqrt{2} s_{\theta_W/2}^2$, $m_H/m_t c_{\theta_W} \simeq 1-\sqrt{2}s_{ \theta_W/2}^2$. In the limit $\cos\theta_W\to 1$ all the masses would become equal $m_Z=m_W=m_t=m_H$. We review the theoretical situation of this ratio in the SM and beyond. In the SM these relations are rather stable under RGE pointing out to some underlying UV symmetry. In the SM such a ratio hints for a non-casual relation of the type $\lambda \simeq \kappa \left (g^2+{g'}{}^2\right )$ with $\kappa\simeq 1+o(g/g_t)$. Moreover the existence of relations $m_i/m_j \simeq f_{ij}(\theta_W)$ could be interpreted as a hint for a role of the $SU(2)_c$ custodial symmetry, together with other unknown mechanism. % Without a symmetry at hand to explain then in the SM, it arises a Higgs mass coincidence problem, why the ratios $\rho_t,\rho_{Wt}$ are so close to one, can we find a mechanism that naturally gives $m_H^2=m_Z m_t$, $2m_H= m_W+m_t$?., Comment: Major changes. figures added

In the frame of the scalar field model with non minimal kinetic coupling to gravity, we study the cosmological solutions of the Chaplygin gas model of dark energy. By appropriately restricting the potential, we found the scalar field, the potential and coupling giving rise to the Chaplygin gas solution. Extensions to the generalized and modified Chaplygin gas have been made., Comment: 18 pages, 2 figures. To appear in EPJC

We use the embedding tensor method to construct the most general maximal gauged/massive supergravity in d=9 dimensions and to determine its extended field content. Only the 8 independent deformation parameters (embedding tensor components, mass parameters etc.) identified by Bergshoeff \textit{et al.} (an SL(2,R) triplet, two doublets and a singlet can be consistently introduced in the theory, but their simultaneous use is subject to a number of quadratic constraints. These constraints have to be kept and enforced because they cannot be used to solve some deformation parameters in terms of the rest. The deformation parameters are associated to the possible 8-forms of the theory, and the constraints are associated to the 9-forms, all of them transforming in the conjugate representations. We also give the field strengths and the gauge and supersymmetry transformations for the electric fields in the most general case. We compare these results with the predictions of the E11 approach, finding that the latter predicts one additional doublet of 9-forms, analogously to what happens in N=2, d=4,5,6 theories., Comment: Latex file, 43 pages, reference added

First we investigate the possibility of detecting solar antineutrinos with the KamLAND experiment. Then we analyze the first Borexino data release to constrain the neutrino magnetic moment. Finally we investigate the resonant spin flavour conversion of solar neutrinos to sterile ones, a mechanism which is added to the well known LMA one. In this last condition, we show that the data from all solar neutrino experiments except Borexino exhibit a clear preference for a sizable magnetic field. We argue that the solar neutrino experiments are capable of tracing the possible modulation of the solar magnetic field. In this way Borexino alone may play an essential role although experimental redundancy from other experiments will be most important., Comment: Contribution to the 44th Rencontres de Moriond in the Electroweak 09. 6 pages, 6 figure, moriond.sty included

We present a common explanation of the fermion mass hierarchy and the large lepton mixing angles in the context of a grand unified flavor and gauge theory (GUTF). Our starting point is a SU(3)xU(1) flavor symmetry and a SO(10) GUT, a basic ingredient of our theory which plays a major role is that two different breaking pattern of the flavor symmetry are at work. On one side, the dynamical breaking of SU(3)xU(1) flavor symmetry into U(2)xZ_3 explains why one family is much heavier than the others. On the other side, an explicit symmetry breaking of SU(3) into a discrete flavor symmetry leads to the observed tribimaximal mixing for the leptons. We write an explicit model where this discrete symmetry group is A4. Naturalness of the charged fermion mass hierarchy appears as a consequence of the continuous SU(3) flavor symmetry. Moreover, the same discrete A4-GUT invariant operators are the root of the large lepton mixing, small Cabibbo angle, and neutrino masses., Comment: 11 pages, uses package "axodraw", "graphicx"

This chapter of the report of the ``Flavour in the era of the LHC'' Workshop discusses the theoretical, phenomenological and experimental issues related to flavour phenomena in the charged lepton sector and in flavour-conserving CP-violating processes. We review the current experimental limits and the main theoretical models for the flavour structure of fundamental particles. We analyze the phenomenological consequences of the available data, setting constraints on explicit models beyond the Standard Model, presenting benchmarks for the discovery potential of forthcoming measurements both at the LHC and at low energy, and exploring options for possible future experiments., Comment: Report of Working Group 3 of the CERN Workshop ``Flavour in the era of the LHC'', Geneva, Switzerland, November 2005 -- March 2007

We present an updated analysis of all available solar and reactor neutrino data, emphasizing in particular the totality of the KamLAND (314d live time) results and including for the first time the solar $SNO$ (391d live time, phase II NaCl-enhanced) spectrum data. As a novelty of the statistical analysis, we study the variability of the KamLand results with respect the use of diverse statistics. A new statistic, not used before is proposed. Moreover, in the analysis of the SNO spectrum a novel technique is used in order to include full correlated errors among bins. Combining all data, we obtain the following best-fit parameters: we determine individual neutrino mixing parameters and their errors $ \Delta m^2= 8.2\pm 0.08\times 10^{-5} \eV^2,\quad \tan^2\theta= 0.50^{+0.12}_{-0.07}.$ The impact of these results is discussed. We also estimate the individual elements of the neutrino mass matrix. In the framework of three neutrino oscillations we obtain the mass matrix: \begin{eqnarray}M&=& eV \pmatrix{1.0+ 4.0\pm 3.2 10^{-5}& 4.2\pm 3.2 10^{-5} &-13.5\pm 14.0 10^{-5} \cr 4.2\pm 3.2 10^{-5}& 1.0+4.3\pm 3.5 10^{-5} &-13.5\pm 14.5 10^{-5} \cr 13.5\pm 14.0 10^{-5}& -13.5\pm 14.5 10^{-5} &1.0+100.0\pm 30.0\ 10^{-5}}.\end{eqnarray}, Comment: Author attributions corrected

The object of this work is the systematical study of a certain type of generalized Cartan matrices associated with the Dynkin diagrams that characterize Cartan-Lie and affine Kac-Moody algebras. These generalized matrices are associated to graphs which arise in the study and classification of Calabi-Yau spaces through Toric Geometry. We focus in the study of what should be considered the generalization of the affine exceptional series $E_{6,7,8}^{(1)}$ Kac-Moody matrices. It has been conjectured that these generalized simply laced graphs and associated link matrices may characterize generalizations of Cartan-Lie and affine Kac-Moody algebras., Comment: Proceedings of the XIII Fall Workshop on Geometry and Physics Murcia, September 20--22, 2004

The algebraic approach to the construction of the reflexive polyhedra that yield Calabi-Yau spaces in three or more complex dimensions with K3 fibres reveals graphs that include and generalize the Dynkin diagrams associated with gauge symmetries. In this work we continue to study the structure of graphs obtained from $CY_3$ reflexive polyhedra. The objective is to describe the ``simply laced'' cases, those graphs obtained from three dimensional spaces with K3 fibers which lead to symmetric matrices. We study both the affine and, derived from them, non-affine cases. We present root and weight structurea for them. We study in particular those graphs leading to generalizations of the exceptional simply laced cases $E_{6,7,8}$ and $E_{6,7,8}^{(1)}$. We show how these integral matrices can be assigned: they may be obtained by relaxing the restrictions on the individual entries of the generalized Cartan matrices associated with the Dynkin diagrams that characterize Cartan-Lie and affine Kac-Moody algebras. These graphs keep, however, the affine structure present in Kac-Moody Dynkin diagrams. We conjecture that these generalized simply laced graphs and associated link matrices may characterize generalizations of Cartan-Lie and affine Kac-Moody algebras.

We present an updated analysis of all available solar and reactor neutrino data, emphasizing in particular the totality of the KamLAND results and including the SNO phase III spectrum data. In a two active-neutrino framework, we determine the solutions in the $\Delta m_{\odot}^2, \tan^2\theta_{\odot}$ parameter space compatible with experimental data. Combining all data, we obtain the following best-fit parameters: $\Delta m_{\odot}^2 =8.17*10^-5$, $\tan^2\theta_{\odot}=0.40$, Comment: 4 figures. Some references added

The algebraic approach to the construction of the reflexive polyhedra that yield Calabi-Yau spaces in three or more complex dimensions with K3 fibres reveals graphs that include and generalize the Dynkin diagrams associated with gauge symmetries. In this work we continue to study the structure of graphs obtained from $CY_3$ reflexive polyhedra. We show how some particularly defined integral matrices can be assigned to these diagrams. This family of matrices and its associated graphs may be obtained by relaxing the restrictions on the individual entries of the generalized Cartan matrices associated with the Dynkin diagrams that characterize Cartan-Lie and affine Kac-Moody algebras. These graphs keep however the affine structure, as it was in Kac-Moody Dynkin diagrams. We presented a possible root structure for some simple cases. We conjecture that these generalized graphs and associated link matrices may characterize generalizations of these algebras., Comment: 24 pages, 6 figures

We present here a recopilation of recent results about the possibility of detecting solar electron antineutrinos produced by solar core and convective magnetic fields. These antineutrinos are predicted by spin-flavor oscillations at a significant rate even if this mechanism is not the leading solution to the SNP. Using the recent Kamland results and assuming a concrete model for antineutrino production by spin-flavor precession in the convective zone based on chaotic magnetic fields,we obtain bounds on the flux of solar antineutrinos, on the average conversion neutrino-antineutrino probability and on intrinsic neutrino magnetic moment. In the most conservative case, $\mu\lsim 2.5\times 10^{-11} \mu_B$ (95% CL). When studying the effects of a core magnetic field, we find in the weak limit a scaling of the antineutrino probability with respect to the magnetic field profile in the sense that the same probability function can be reproduced by any profile with a suitable peak field value. In this way the solar electron antineutrino spectrum can be unambiguosly predicted. We use this scaling and the negative results indicated by the KamLAND experiment to obtain upper bounds on the solar electron antineutrino flux. We find that, for a wide family of magnetic field profiles in the sun interior, the antineutrino appearance probability is largely determined by the magnetic field intensity but not by its shape. Explicit limits on neutrino transition moments are also obtained consistent with the convective case. These limits are therefore largerly independent of the detailed structure of the magnetic field in the solar interior., Comment: Expanded version of a presentation contributed to `` 8th International Workshop On Topics In Astroparticle And Underground Physics (TAUP 2003)''

An updated analysis of all available neutrino oscillation evidence in Solar experiments including the latest SNO ES,CC and NC data (254d live time, NaCL enhanced efficiency) is presented. We obtain, for the fraction of active oscillating neutrinos: sin^2alpha=(\Phi_{NC}-\Phi_{CC})/(\Phi_{SSM}-\Phi_{CC})=0.94^{+0.0.065}_{-0.060} nearly 20\sigma from the pure sterile oscillation case. The fraction of oscillating sterile neutrinos cos^2\alpha \lsim 0.12 (1 sigma CL). At face value, these results might slightly favour the existence of a small sterile oscillating sector. In the framework of two active neutrino oscillations we determine individual neutrino mixing parameters and their errors we obtain Delta m^2= 7.01\pm 0.08 \times 10^{-5} eV^2, tan^2 theta=0.42^{+0.12}_{-0.07}. The main difference with previous analysis is a better resolution in parameter space. In particular the secondary region at larger mass differences (LMAII) is now excluded at 95% CL. The combined analysis of solar and Kamland data concludes that maximal mixing is not favoured at 4-5 sigma. This is not supported by the antineutrino reactor results alone. We estimate the individual elements of the two neutrino mass matrix, writing M^2=m^2 I+M_0^2, we obtain (1 sigma errors): M_0^2=10^{-5} eV^2\pmatrix{ 2.06^{+0.29}_{-0.31} & 3.15^{+0.29}_{-0.35} \cr 3.15^{+0.29}_{-0.35} & 4.60^{+0.56}_{-0.44} }.

We use the recent KamLAND observations to predict the solar antineutrino spectrum at some confidence limits. We find that a scaling of the antineutrino probability with respect to the magnetic field profile --in the sense that the same probability function can be reproduced by any profile with a suitable peak field value-- can be utilised to obtain a general shape of the solar antineutrino spectrum. This scaling and the upper bound on the solar antineutrino event rate, that can be derived from the data, lead to: 1) an upper bound on the solar antineutrino flux, 2) the prediction of their energy spectrum, as the normalisation of the spectrum can be obtained from the total number of antineutrino events recorded in the experiment. We get $\phi_{\bar\nu}<3.8\times 10^{-3}\phi(^8B)$ or $\phi_{\bar\nu} <5.5\times 10^{-3}\phi(^8B)$ at 95% CL, assuming Gaussian or Poissonian statistics, respectively. And for 90% CL these become $\phi_{\bar\nu}<3.4 \times 10^{-3}\phi(^8B)$ and $\phi_{\bar\nu}<4.9\times 10^{-3}\phi(^8B)$. It shows an improvement by a factor of 3-5 with respect to existing bounds. These limits are quite general and independent of the detailed structure of the magnetic field in the solar interior., Comment: Based on talk given at NANP'03, JINR Dubna, Russia, June 2003. To be published in "Physics of Atomic Nuclie"

In this work the possibility of detecting solar electron antineutrinos produced by a solar core magnetic field from the KamLAND recent observations is investigated. We find a scaling of the antineutrino probability with respect to the magnetic field profile in the sense that the same probability function can be reproduced by any profile with a suitable peak field value. In this way the solar electron antineutrino spectrum can be unambiguosly predicted. We use this scaling and the negative results indicated by the KamLAND experiment to obtain upper bounds on the solar electron antineutrino flux. We get $\phi_{\bar\nu}<3.8\times 10^{-3}\phi(^8B)$ at 95% CL. For 90% CL this becomes $\phi_{\bar\nu}<3.4\times 10^{-3}\phi(^8B)$, an improvement by a factor of 3-5 with respect to existing bounds. These limits are independent of the detailed structure of the magnetic field in the solar interior. We also derive upper bounds on the peak field value which are uniquely determined for a fixed solar field profile. In the most efficient antineutrino producing case, we get (95% CL) an upper limit on the product of the neutrino magnetic moment by the solar field $\mu B< 2.8\times 10^{-19}$ MeV or $B_0 \leq 4.9 \times 10^7 G$ for $\mu_\nu=10^{-12}\mu_B$., Comment: 15 pages. References corrected. Minor changes in the text

We investigate the possibility of detecting solar electron antineutrinos with the KamLAND experiment. These electron antineutrinos are predicted by spin-flavor oscillations at a significant rate even if this mechanism is not the leading solution to the SNP. KamLAND is sensitive to antineutrinos originated from solar ${}^8$B neutrinos. From KamLAND negative results after 145 days of data taking, we obtain model independent limits on the total flux of solar electron antineutrinos $\Phi({}^8 B)< 1.1-3.5\times 10^4 cm^{-2}\ s^{-1}$, more than one order of magnitude smaller than existing limits, and on their appearance probability $P<0.15%$ (95% CL). Assuming a concrete model for antineutrino production by spin-flavor precession, this upper bound implies an upper limit on the product of the intrinsic neutrino magnetic moment and the value of the solar magnetic field $\mu B< 2.3\times 10^{-21}$ MeV 95% CL (for LMA $(\Delta m^2, \tan^2\theta)$ values). Limits on neutrino transition moments are also obtained. For realistic values of other astrophysical solar parameters these upper limits would imply that the neutrino magnetic moment is constrained to be, in the most conservative case, $\mu\lsim 3.9\times 10^{-12} \mu_B$ (95% CL) for a relatively small field $B= 50$ kG. For higher values of the magnetic field we obtain: $\mu\lsim 9.0\times 10^{-13} \mu_B$ for field $B= 200$ kG and $\mu\lsim 2.0\times 10^{-13} \mu_B$ for field $B= 1000$ kG at the same statistical significance., Comment: 13 pages, 2 figures

An updated analysis of all available neutrino oscillation evidence in Reactor (Kamland, first 145 days of data) and Solar experiments (SK day and night spectra, global rates from Homestake, SAGE and GALLEX) including the $SNO CC$ and $NC$ data is presented. In the framework of two active neutrino oscillations we determine the allowed regions in neutrino parameter space, we obtain, from the Kamland spectral shape and global signal, the following antineutrino best solution parameters, $ \Delta m^2_{kl}= 7.7\times 10^{-5} \eV^2, \tan^2\theta_{kl}= 0.98.$ The overall effect of the measured observed ratio $R\sim 0.6$ is that the LMA region remains the only one which is still favored. Combining Kamland and Solar data and assuming CPT invariance, i.e. the same mass matrix for neutrino and antineutrinos, we obtain the following antineutrino best solution parameters (LMAI solution), $ \Delta m^2= 7.1\times 10^{-5} \eV^2,\tan^2\theta= 0.47.$ A second solution (LMAII) appears for values $ \Delta m^2= 1.5\times 10^{-4} \eV^2, \tan^2\theta= 0.48.$ We determine additionally individual neutrino mixing parameters and their errors from fits to marginal likelihood distributions, the values are compatible with previous results. In both methods, $\chi^2$ minimization and marginal likelihood, the combined analysis of solar and Kamland data concludes that maximal mixing is not favored at the $\sim 3\sigma $ level at least.

We present a short review of the existing evidence in favor of neutrino mass and neutrino oscillations which come from different kinds of experiments. We focus our attention in particular on solar neutrinos, presenting a review of some recent analysis of all available neutrino oscillation evidence in Solar experiments including the recent $SNO CC$ and $NC$ data. We present in detail the power of the reactor experiment KamLAND for discriminating existing solutions to the SNP and giving accurate information on neutrino masses and mixing angles., Comment: Expanded version of the contribution to appear in the Proceedings of ''Third Tropical Workshop on Particle Physics and Cosmology: Neutrinos, Branes and Cosmology (Puerto Rico, August 2002)''

We review the calculation of the LSP relic density in alternative cosmological scenarios where contributions from direct decay production are important. We study supersymmetric models with intermediate unification scale. We find concrete scenarios where the reheating temperature is of order one GeV ($M_I\sim 10^{12}$) and below. If the case that this reheating temperature is associated to the decay of oscillating moduli fields appearing in string theories, we show that the LSP relic density considerably increases with respect to the standard radiation-dominated case by the effect of the direct non-thermal production by the modulus field. The LSP can become a good dark matter candidate ($0.01-0.1 \gsim \Omega h^2 \lsim 0.3-1$) for $M_I\sim 10^{12}-10^{14}$ Gev and $m_\phi\sim 1-10$ TeV., Comment: Expanded version of the contribution in NEUTRINO2002, May 25-30,2002, Munich, Germany. The work presented here was made and published in collaboration with S. Khalil and C. Munoz

We review here the development of the general formalism for the study of fermion propagation in the presence of stochastic media. This formalism allows the systematic derivation of evolution equations for averaged quantities as survival probabilities and higher order distribution moments. The formalism equally applies to any finite dimensional Schr\"{o}dinger equation in the presence of a stochastic external field. New integrodifferential equations valid for finite correlated processes are obtained for the first time. For the particular case of exponentially correlated processes a second order ordinary equation is obtained. As a consequence, the Redfield equation valid for Gaussian delta-correlated noise is rederived in a simple way: it has been obtained directly and as the zero-order term of an asymptotic expansion in the inverse of the correlation length. The formalism, together with the quantum correlation theorem is applied to the computation of higher moments and correlation functions. It is shown that equal and unequal time correlators follow similar differential equations., Comment: Expanded version of the contribution in ``Field Theory and Statistical Mechanics, Rome 10-15 June 2002''

We investigate the possibility of detecting solar antineutrinos with the KamLAND experiment. These antineutrinos are predicted by spin-flavor oscillations at a significant rate even if this mechanism is not the leading solution to the SNP. The recent evidence from SNO shows that a) the neutrino oscillates, only around 34% of the initial solar neutrinos arrive at the Earth as electron neutrinos and b) the conversion is mainly into active neutrinos, however a non e, mu, tau component is allowed: the fraction of oscillation into non-mu-tau neutrinos is found to be cos^2(alpha) = 0.08^{+0.20}_{-0.40}. This residual flux could include sterile neutrinos and/or the antineutrinos of the active flavors. KamLAND is potentially sensitive to antineutrinos derived from solar ^8 B neutrinos. In case of negative results, we find that KamLAND could put strict limits on the flux of solar antineutrinos, Phi(^8 B) < 1.0 times 10^4 cm^{-2} s^{-1}, more than one order of magnitude smaller than existing limits, and on their appearance probability P < 0.20-0.15% (95% CL) after 1-3 years of operation. Assuming a concrete model for antineutrino production by spin-flavor precession, this upper bound implies an upper limit on the product of the intrinsic neutrino magnetic moment and the value of the solar magnetic field mu B < 10^{-21} MeV (95% CL). For B ~ 10-100 kG, we would have mu < 10^{-11}-10^{-12} mu_B (95% CL). In the opposite case, if spin-flavor precession is indeed at work even at a non-leading rate, the additional flux of antineutrinos could strongly distort the signal spectrum seen at KamLAND at energies above 4-5 MeV and their contribution should properly be taken into account.

We study in detail the power of the reactor experiment kamLAND for discriminating existing solutions to the SNP and giving accurate information on neutrino masses and mixing angles. Assuming the expected signal corresponding to various ``benchmark'' points in the 2 dimensional $(\Delta m^2,\tan^2 \theta)$ mixing plane, we develop a full-fledged $\chi^2$ analysis which includes KamLAND spectrum and all the existing solar evidence. A complete modelling of statistical and known systematics errors for 1 and 3 years of data taking is also included, exclusion plots are presented. We find a much higher sensitivity especially for values of $\Delta m^2$ lying in the central part of the LMA region. The situation would be more complicate for values closer to the border of the LMA region (the so called HLMA region, i.e. $\Delta m^2 \leq 2 \times 10^{5}$ and $\Delta m^2 \geq 8-9 \times 10^{-5}$ or $tan^2 \theta$ far from $\tan^2 \theta = 0.5$). In this case kamLAND, with or without solar evidence, will be able only to select multiple regions in the parameter space, in the sense that different possible values of the parameters would produce the same signal., Comment: IFUM-345-FT,FTUAM-02-765

We present a short review of the existing evidence in favor of neutrino mass and neutrino oscillations which come from different kinds of experiments. We focus our attention in particular on solar neutrinos, presenting a global updated phenomenological analysis of all the available data and we comment on different possible future scenarios., Comment: 22 pp. Expanded version of the contribution to appear in the Proceedings of ``Les Rencontres de Physique de la Vallee d'Aoste'', February 2002

We analyze the expected signals of two future neutrino experiments, kamLAND and BOREXINO. We show that with just these experiments, we will hopefully be able to determine which of the existing solutions to the solar neutrino problem is the real solution. We also analyze existing solar neutrino data and determine the best-fit points in the oscillation-parameter space finding that with the inclusion of SNO-charged current, the global-rates analysis gives a favored LMA solution with a goodness of fit (g.o.f) of just 32.63%, whereas the g.o.f of the SMA solution is 9.83%. Nonetheless, maximal and quasi-maximal mixing is not favored. If we include the Superkamiokande spectrum in our \chi^2 analysis, we obtain a LMA solution with a g.o.f. of 84.38%., Comment: 4 pages, 5 figures, Talk given at 37th Rencontres de Moriond on Electroweak Interactions and Unified Theories, Les Arcs, France, 9-16 Mar 2002

An updated analysis of all available neutrino oscillation evidence in Solar experiments (SK day and night spectra, global rates from Homestake, SAGE and GALLEX) including the latest SNO CC and NC data is presented. Assuming that the shape of the SNO CC energy spectrum is undistorted and using the information provided by SNO we obtain, for the fraction of electron neutrinos remaining in the solar beam at energies $\gsim 5$ MeV: $\phi_{CC}/\phi_{NC}=0.34^{+0.05}_{-0.04},$ which is nominally $\sim 30\sigma$ away from the standard value. The fraction of oscillating neutrinos which into active ones is computed to be: $ (\Phi_{NC}-\Phi_{CC})/(\Phi_{SSM}-\Phi_{CC})=0.92^{+0.39}_{-0.20} $ nearly $5\sigma$ deviations from the pure sterile oscillation case. The data is still compatible with an important fraction of sterile component in the solar beam (up to 20% of the total). In the framework of two active neutrino oscillations we determine individual neutrino mixing parameters and their errors in the region of no spectrum distortion ($\Delta< T_e> <1%$), we obtain $\Delta m^2= 4.5^{+2.7}_{-1.4}\times 10^{-5} \eV^2, \quad \tan^2\theta=0.40^{+0.10}_{-0.08}. $ This is in agreement with the best $chi^2$ solution in the LMA region.

We analyse the relic neutralino density in supersymmetric models with an intermediate unification scale. In particular, we present concrete cosmological scenarios where the reheating temperature is as small as $\cal{O}$ $1 - 1000$ MeV). When this temperature is associated to the decay of moduli fields producing neutralinos, we show that the relic abundance increases considerably with respect to the standard thermal production. Thus the neutralino becomes a good dark matter candidate with $0.1\lsim \Omega h^2 \lsim 0.3$, even for regions of the parameter space where large neutralino-nucleon cross sections, compatible with current dark matter experiments, are present. This is obtained for intermediate scales $M_I\sim 10^{11}-10^{14}$ GeV, and moduli masses $m_\phi\sim 100-1000$ GeV. On the other hand, when the above temperature is associated to the decay of an inflaton field, the relic abundance is too small., Comment: Latex, 11 pages, 2 figures

We present an updated analysis of all the data available about solar neutrinos, including the charged current SNO results. The best fit of the data is obtained in the Large Mixing Angle region, but different solutions are still possible. We also study the perspectives of Borexino and conclude that this experiment, with a parallel analysis of total rate and day-night asymmmetry, should be able to discriminate between the different possible solutions., Comment: 3 pages, Latex, talk given by V. Antonelli at TAUP 2001 Conference

An updated analysis of all available neutrino oscillation evidence in Solar experiments including the latest $SNO$ data is presented. Predictions for total rates and day-night asymmetry in Borexino are calculated. Our analysis features the use of exhaustive computation of the neutrino oscillation probabilities and the use of an improved statistical $\chi^2$ minimization. In the framework of two neutrino oscillations we conclude that the best fit to the data is obtained in the LMA region with parameters $(\Delta m^2, \tan^2\theta) = (5.2 \times 10^{-5} \eV^2, 0.47)$, ($\chi^2_{min}/n=0.82$, $n=38$ degrees of freedom). Although less favored, solutions in the LOW and VAC regions are still possible with a reasonable statistical significance. The best possible solution in the SMA region gets as maximum a statistical significance as low as $\sim 3%$. We study the implications of these results for the prospects of Borexino and the possibility of discriminating between the different solutions. The expected normalized Borexino signal is 0.62 at the best fit LMA solution while the DN asymmetry is negligible (approximately $10^{-5}$). In the LOW region the signal is in the range $\sim 0.6-0.7$ at 90% confidence level while the asymmetry is $\simeq 1-20%$. As a consequence, the combined Borexino measurements of the total event rate with a error below $\pm 5-10%$ and day-night total rate asymmetry with a precision comparable to the one of SuperKamiokande, will have a strong chance of distinguishing or at least strongly favoring one of the Solar neutrino solutions provided by present data., Comment: 24 pages, 9 figures, better resolution figures are available upon request

We analyze the anomalous magnetic moment of the muon (a_{\mu}) in supersymmetric scenarios. First we concentrate on scenarios with universal soft terms. We find that a moderate increase of a_{\mu} can be obtained by lowering the unification scale M_{GUT} to intermediate values 10^{10-12} GeV. However, large values of \tan \beta are still favored. Then we study the case of non-universal soft terms. For the usual value M_{GUT}~10^{16} GeV, we obtain a_{\mu} in the favored experimental range even for moderate \tan \beta regions \tan\beta ~ 5$. Finally, we give an explicit example of these scenarios. In particular, we show that in a D-brane model, where the string scale is naturally of order 10^{10-12} GeV and the soft terms are non universal, a_{\mu} is enhanced with low \tan\beta., Comment: Final version to appear in Phys. Rev. D. Conventions clarified, results in the figures improved

We analyze different phenomenological aspects of D-brane constructions. First, we obtain that scenarios with the gauge group and particle content of the supersymmetric standard model lead naturally to intermediate values for the string scale, in order to reproduce the value of gauge couplings deduced from experiments. Second, the soft terms, which turn out to be generically non universal, and Yukawa couplings of these scenarios are studied in detail. Finally, using these soft terms and the string scale as the initial scale for their running, we compute the neutralino-nucleon cross section. In particular we find regions in the parameter space of D-brane scenarios with cross sections in the range of $10^{-6}$--$10^{-5}$ pb, i.e. where current dark matter experiments are sensitive. For instance, this can be obtained for $\tan\beta > 5$., Comment: Figures improved, misprints corrected, results basically unchanged

We present a review of the present status of the problem of neutrino masses and mixing including a survey of theoretical motivations and models, experimental searches and implications of recently appeared solar and atmospheric neutrino data, which strongly indicate nonzero neutrino masses and mixing angles., Comment: Invited review article to appear in the Journal of the Egiptian Mathematical Society. 52 pages, 10 figures

The neutralino-nucleon cross section in the context of the MSSM with universal soft supersymmetry-breaking terms is compared with the limits from dark matter detectors. Our analysis is focussed on the stability of the corresponding cross sections with respect to variations of the initial scale for the running of the soft terms, finding that the smaller the scale is, the larger the cross sections become. For example, by taking $10^{10-12}$ GeV rather than $M_{GUT}$, which is a more sensible choice, in particular in the context of some superstring models, we find extensive regions in the parameter space with cross sections in the range of $10^{-6}$--$10^{-5}$ pb, i.e. where current dark matter experiments are sensitive. For instance, this can be obtained for $\tan\beta\gsim 3$., Comment: Improved references, new comments added

We analyse the predictions for the inclusive branching ratio for $b\to s\gamma$ decay in a class of string-inspired SUSY models with non-universal soft-breaking A-terms. These models are particularly interesting since the non-universality of the A-terms plays an important role in providing new significant contributions to CP violation effects in kaon physics while respecting the severe bounds on electric dipole moments. We show that $b\to s\gamma$ do not severely constrain the non-universality of these models. In particular, at low $\tan\beta$ $(\tan\beta\simeq 2)$, our predictions are close to the universal case. For large $\tan\beta$ ($\tan\beta \gsim 15$),the effect of non-universality is enhanced and stronger constraints hold. We find that the parameter regions which are important for generating sizeable contribution to $\epsilon'/\epsilon$, of order $2 \times 10^{-3}$, are not excluded., Comment: 27 latex pages, with 6 figures in 11 eps files

We consider the effect of a random magnetic field in the convective zone of the Sun on resonant neutrino spin-flavour oscillations. The expected signals in the different experiments (SK, GALLEX-SAGE,Homestake) are obtained as a function of the level of noise, regular magnetic field and neutrino mixing parameters. Previous results obtained for small mixing and ad-hoc regular magnetic profiles are reobtained. We find that MSW regions are stable up to very large levels of noise (P=0.7-0.8) and they are acceptable from the point of view of antineutrino production. For strong noise any parameter region $(\Delta m^2, \sin^2 2\theta)$ is excluded: this model of noisy magnetic field is not compatible with particle physics solutions to the SNP. scenario., Comment: 10pp+2figs. To be published in the proceedings of 2nd ICRA Network Workshop: The Chaotic Universe: Theory and observations, Rome, Italy, 1-5 Feb 1999

A search for inverse beta decay electron antineutrinos has been carried out using the 825 days sample of solar data obtained at SK. The absence of a significant signal, that is, contributions to the total SK background and their angular variations has set upper bounds on a) the absolute flux of solar antineutrinos originated from ${}^8 B$ neutrinos $\Phi_{\bar{\nu}}({}^8 B)=< 1.8\times 10^5 cm^{-2} s^{-1}$ which is equivalent to an averaged conversion probability bound of P<3.5% (SSM-BP98 model) and b) their differential energy spectrum, the conversion probability is smaller than 8% for all $E_{e,vis}>6.5$ MeV going down the 5% level above $E_{e,vis}\approx 10$ MeV. It is shown that an antineutrino flux would have the net effect of enhancing the SK signal at {\em hep} neutrino energies. The magnitude of this enhancement would highly depend on the, otherwise rather uncertain, steepness of the solar neutrino spectrum at these energies., Comment: 5 pages, 3 ps figures

The experimental measurement of $B(b \to s\gamma)$ imposes important constraints on the charged Higgs boson mass in the MSSM. We show that by adding bilinear R--Parity violation (BRpV) in the tau sector, these bounds are relaxed. The bound on $m_{H^{\pm}}$ in the MSSM--BRpV model is $\gsim 200-250$ GeV for the the heavy squark limit. For lighter squarks, light charged Higgs bosons can be reconciled with $B(b \to s\gamma)$ only if there is also a light chargino. In the BRpV model if we impose $m_{\chi^{\pm}_1}>90$ GeV $m_{H^{\pm}} \gsim 75$ GeV, around 30 GeV down from the MSSM. In this case the charged Higgs bosons would be observable at LEP II. The relaxation of the bounds is due mainly to the fact that charged Higgs bosons mix with staus and they contribute importantly to $B(b \to s\gamma)$., Comment: Based on work made in collaboration with M. A. D\'\i az and J. W. F. Valle and presented at: ``TMR Network on Physics beyond the SM''. Trieste, February 1999.}

We present a short review of the present status of the problem of neutrino masses and mixing including a survey of theoretical motivations and models, experimental searches and implications of recently appeared solar and atmospheric neutrino data, which strongly indicate nonzero neutrino masses. Such data apparently requires the existence of light sterile neutrino in addition to the three active ones and two-generation nearly maximal mixing., Comment: 24 pags, 9 figs