For Majorana or Dirac neutrinos, using Fritzsch-like texture 4 zero mass matrices with parallel texture structures for the charged leptons and the Dirac neutrino mass matrix ($M_{\nu D}$), detailed predictions for cases pertaining to normal/inverted hierarchy as well as degenerate scenarios of neutrino masses have been carried out. The inverted hierarchy as well as degenerate scenarios seem to be ruled out at $3\sigma$ C.L. for both Majorana and Dirac neutrinos. For normal hierarchy, Jarlskog’s rephasing invariant parameter $J$, the $CP$ violating Dirac-like phase $\delta$, and the effective neutrino mass $⟨m_{ee}⟩$ have been calculated. For this case, lower limits of $m_{{\nu }_1}$ and ${\theta }_{13}$ would have implications for the nature of neutrinos.

Using $e^{+}{e}^{-}\to \mathrm{\text{hadrons}}$ data collected with the CLEO-III detector at the Cornell Electron Storage Ring, we study the inclusive production of baryons/antibaryons $(p,\Lambda )$ and mesons ($\varphi$ and $f_2(1270)$) in gluon-fragmentation and quark-fragmentation processes. We first corroborate previous per-event total particle yields in ${\rm Y}(1\mathrm{S})\to ggg$ compared with nearby continuum ($e^{+}{e}^{-}\to q\overline{q}$) indicating greater ($\sim \times 2$) per-event yields of baryons in 3-gluon fragmentation. We find similar results when we extend that comparison to include the ${\rm Y}(2\mathrm{S})$ and ${\rm Y}(3\mathrm{S})$ resonances. With higher statistics, we now also probe the momentum dependence of these per-event particle yields. Next, we compare particle production in the photon-tagged process ${\rm Y}(1\mathrm{S})\to gg\gamma$ with that in $e^{+}{e}^{-}\to q\overline{q}\gamma$ events, to allow comparison of two-parton with three-parton particle-specific fragmentation. For each particle, we determine the “enhancement” ratio, defined as the ratio of particle yields per gluon-fragmentation event compared to quark-fragmentation event. Thus defined, an enhancement of 1.0 implies equal per-event production in gluon and quark fragmentation. In the photon-tagged analysis (${\rm Y}(1\mathrm{S})\to gg\gamma$ compared to $e^{+}{e}^{-}\to q\overline{q}\gamma$), we find almost no enhancement for protons ($\sim 1.2\pm 0.1$), but a significant enhancement ($\sim 1.9\pm 0.3$) for $\Lambda$’s. This small measured proton enhancement rate is supported by a study of baryon production in ${\chi }_{b2}\to gg\to p+X$ relative to ${\chi }_{b1}\to q\overline{q}g\to p+X$. Overall, per-event baryon production in radiative two-gluon fragmentation is somewhat smaller than that observed in three-gluon decays of the ${\rm Y}(1\mathrm{S})$. Our results for baryon production are inconsistent with the predictions of the JETSET (7.3) fragmentation model.

An attempt to construct the “ground state” vacuum initial data for the gravitational field surrounding two black holes is presented. The ground state is defined as the gravitational initial data minimizing the ADM mass within the class of data for which the masses of the holes and their distance are fixed. To parametrize different geometric arrangements of the two holes (and, therefore, their distance), we use an appropriately chosen scale factor. A method for analyzing the variations of the ADM mass and the masses (areas) of the horizons in terms of gravitational degrees of freedom is proposed. The Misner initial data are analyzed in this context: it is shown that they do not minimize the ADM mass.

Recently, P. M. Brooks and C. J. Maxwell [Phys. Rev. D 74, 065012 (2006)] claimed that the Landau pole of the one-loop coupling at $Q^2={\Lambda }^2$ is absent from the leading one-chain term in a skeleton expansion of the Euclidean Adler $\mathcal{D}$ function. Moreover, in this approximation one has, allegedly, continuity along the Euclidean axis and a smooth infrared freezing, properties known to be satisfied by the “true” Adler function. We show that crucial in the derivation of these results is the use of a modified Borel summation, which leads simultaneously to the loss of another fundamental property of the true Adler function: the analyticity implied by the Källen-Lehmann representation.

Using the gauge-invariant but path-dependent variables formalism, we compute the static quantum potential for noncommutative axionic electrodynamics, and find a radically different result than the corresponding commutative case. We explicitly show that the static potential profile is analogous to that encountered in both non-Abelian axionic electrodynamics and in Yang-Mills theory with spontaneous symmetry breaking of scale symmetry.

We analyze the semiclassical Einstein equations for quantum scalar fields satisfying modified dispersion relations. We first discuss in detail the renormalization procedure based on adiabatic subtraction and dimensional regularization. We show that, contrary to what is expected from power counting arguments, in $3+1$ dimensions the subtraction involves up to the fourth adiabatic order even for dispersion relations containing higher powers of the momentum. Then we analyze the dependence of the trace of the renormalized energy-momentum tensor with the scale of new physics, and we recover the usual trace anomaly in the appropriate limit. We also find self-consistent de Sitter solutions for dispersion relations that contain up to the fourth power of the momentum. Using this particular example, we also discuss the possibility that the modified dispersion relation can be mimicked at lower energies by an effective initial state in a theory with the usual dispersion relation.

Five and six dimensional static, spherically symmetric, asymptotically Euclidean black holes, are unstable under gravitational perturbations if their mass is lower than a critical value set by the string tension. The instability is due to the Gauss-Bonnet correction to Einstein’s equations, and was found in a previous work on linear stability of Einstein-Gauss-Bonnet black holes with constant curvature horizons in arbitrary dimensions. We study the unstable cases and calculate the values of the critical masses. The results are relevant to the issue of black hole production in high energy collisions.

It is well known that there exists a Hawking-Page phase transition between a spherical anti-de Sitter (AdS) black hole and a thermal AdS space. The phase transition does not happen between a Ricci flat AdS black hole whose horizon is a Ricci flat space and a thermal AdS space in the Poincaré coordinates. However, the Hawking-Page phase transition occurs between a Ricci flat AdS black hole and an AdS soliton if at least one of the horizon coordinates for the Ricci flat black hole is compact. We show a similar phase transition between the Ricci flat black holes and deformed AdS solitons in the Gauss-Bonnet gravity and the dilaton gravity with a Liouville-type potential including the gauged supergravity coming from the spherical reduction of Dp branes in type II supergravity. In contrast to Einstein gravity, we find that the high temperature phase can be dominated either by black holes or deformed AdS solitons depending on parameters.

The conical singularity in flat spacetime is mostly known as a model of the cosmic string or the wedge disclination in solids. Another, equally important, function is to be a representative of quasiregular singularities. From all these points of view it seems interesting to find out whether there exist other similar singularities. To specify what “similar” means I introduce the notion of the stringlike singularity, which is, roughly speaking, an absolutely mild singularity concentrated on a curve or on a 2-surface $\mathcal{S}$ (depending on whether the space is three- or four-dimensional). A few such singularities are already known: the aforementioned conical singularity, its two Lorentzian versions, the “spinning string,” the “screw dislocation,” and Tod’s spacetime. In all these spacetimes $\mathcal{S}$ is a straight line (or a plane) and one may wonder if this is an inherent property of the stringlike singularities. The aim of this paper is to construct stringlike singularities with less trivial $\mathcal{S}$. These include flat spacetimes in which $\mathcal{S}$ is a spiral, or even a loop. If such singularities exist in nature (in particular, as an approximation to gravitational field of strings), their cosmological and astrophysical manifestations must differ drastically from those of the conventional cosmic strings. Likewise, being realized as topological defects in crystals, such loops and spirals will probably also have rather unusual properties.

We derive the equation of matter density perturbations on subhorizon scales for a general Lagrangian density $f(R,\varphi ,X)$ that is a function of a Ricci scalar $R$, a scalar field $\varphi$, and a kinetic term $X=-(\nabla \varphi {)}^2/2$. This is useful to constrain modified gravity dark energy models from observations of large-scale structure and weak lensing. We obtain the solutions for the matter perturbation ${\delta }_m$ as well as the gravitational potential $\Phi$ for some analytically solvable models. In an $f(R)$ dark energy model with the Lagrangian density $f(R)=\alpha R^{1+m}-\Lambda$, the growth rates of perturbations exhibit notable differences from those in the standard Einstein gravity unless $m$ is very close to 0. In scalar-tensor models with the Lagrangian density $f=F(\varphi )R+2p(\varphi ,X)$, we relate the models with coupled dark energy scenarios in the Einstein frame and reproduce the equations of perturbations known in the current literature by making a conformal transformation. We also estimate the evolution of perturbations in both Jordan and Einstein frames when the energy fraction of dark energy is constant during the matter-dominated epoch.

We reconsider trans-Planckian corrections to inflationary spectra by taking into account a physical effect which has been overlooked and which could have important consequences. We assume that the short length scale characterizing the new physics is endowed with a finite width, the origin of which could be found in quantum gravity. As a result, the leading corrections responsible for superimposed oscillations in the cosmic microwave background temperature anisotropies are generically damped by the blurring of the UV scale. To determine the observational ramifications of this damping, we compare it to that which effectively occurs when computing the angular power spectrum of temperature anisotropies. The former gives an overall change of the oscillation amplitudes whereas the latter depends on the angular scale. Therefore, in principle they could be distinguished. In any case, the observation of superimposed oscillations would place a tight constraint on the variance of the UV cutoff.

We extend next-to-leading logarithmic threshold and joint resummation for prompt photon production to include leading collinear effects. The impact of these effects is assessed for both fixed-target and collider kinematics. We find them in general to be small but noticeable.

Assuming the Dirac-type neutrino masses $m_D$ are related to quark or charged lepton masses, neutrino oscillation data indicate that right-handed neutrino masses are in general strongly hierarchical. In particular, if $m_D$ is similar to the up-type quark masses, the mass of the lightest right-handed neutrino $M_1\lesssim {10}^6\mathrm{GeV}$. We show that nonthermal leptogenesis by inflaton decay can yield sufficient baryon asymmetry despite this constraint, and discuss how the asymmetry is correlated with the low energy neutrino masses and $CP$-violating phases.

We study the possibility that dark energy decays in the future and the universe stops accelerating. The fact that the cosmological observations prefer an equation of state of dark energy smaller than $-1$ can be a signal that dark energy will decay in the future. This conclusion is based in interpreting a $w<-1$ as a signal of dark energy interaction with another fluid. We determine the interaction through the cosmological data and extrapolate it into the future. The resulting energy density for dark energy becomes ${\rho }_{\varphi }={\rho }_{\varphi o}{a}^{-3(1+w_{\varphi })}{e}^{-\beta (a-1)}$, i.e. it has an exponential suppression for $a\gg a_o=1$. In this scenario the universe ends up dominated by this other fluid, which could be matter, and the universe stops accelerating at some time in the near future.

Weakly coupled, almost massless, spin 0 particles have been predicted by many extensions of the standard model of particle physics. Recently, the PVLAS group observed a rotation of polarization of electromagnetic waves in vacuum in the presence of transverse magnetic field. This phenomenon is best explained by the existence of a weakly coupled light pseudoscalar particle. However, the coupling required by this experiment is much larger than the conventional astrophysical limits. Here we consider a hypothetical self-interacting pseudoscalar particle which couples weakly with visible matter. Assuming that these pseudoscalars pervade the galaxy, we show that the solar limits on the pseudoscalar-photon coupling can be evaded.

The effect of the gauge transformation in the action principle for Hamiltonian gauge systems formulated in terms of noncanonical symplectic structures is studied and, particularly, the compatibility between gauge conditions and boundary conditions is analyzed. It is shown that the complete set of commuting observables at the time boundary is now fixed by the boundary term and the symplectic structure. The theory is applied to two nontrivial models having $SL(2,\mathbb{R})$ and $SU(2)$ gauge symmetries, respectively, whose extended phase spaces are endowed with new interactions produced by noncanonical symplectic structures.

An asymptotically flat static solution of Einstein-Maxwell equations which describes the field of two nonextreme Reissner-Nordström sources in equilibrium is presented. It is expressed in terms of physical parameters of the sources (their masses, charges, and separating distance). Very simple analytical forms were found for the solution as well as for the equilibrium condition which guarantees the absence of any struts on the symmetry axis. This condition shows that the equilibrium is not possible for two black holes or for two naked singularities. However, in the case when one of the sources is a black hole and another one is a naked singularity, the equilibrium is possible at some distance separating the sources. It is interesting that for appropriately chosen parameters even a Schwarzschild black hole together with a naked singularity can be “suspended” freely in the superposition of their fields.

Charmed meson production in semi-inclusive deep inelastic scattering is investigated in the color-dipole formalism. The transverse momentum distributions are calculated. We find good agreement with the H1 data using a hard fragmentation function.

Chiral solitons with baryon number one are investigated in the spectral quark model. In this model the quark propagator is a superposition of complex-mass propagators weighted with a suitable spectral function. This technique is a method of regularizing the effective quark theory in a way preserving many desired features crucial in analysis of solitons. We review the model in the vacuum sector, stressing the feature of the absence of poles in the quark propagator. We also investigate in detail the analytic structure of meson two-point functions. We provide an appropriate prescription for constructing valence states in the spectral approach. The valence state in the baryonic soliton is identified with a saddle point of the Dirac eigenvalue treated as a function of the spectral mass. Because of this feature the valence quarks never become unbound nor dive into the negative spectrum, hence providing stable solitons as absolute minima of the action. This is a manifestation of the absence of poles in the quark propagator. Self-consistent mean-field hedgehog solutions are found numerically and some of their properties are determined and compared to previous chiral soliton models. Our analysis constitutes an involved example of a treatment of a relativistic complex-mass system.