We investigate the fluctuation effects of a gap parameter in color superconductors. The fluctuation modes are described as the collective motion of a diquark field. One of the modes is a massless Nambu-Goldstone boson and the other is a diquark boson whose mass is twice the gap energy. It is also shown that in the normal phase the fluctuation mode becomes a precursory (soft) mode whose mass and decay width are calculated near the critical temperature. We discuss the temperature dependence of such quantities in detail.

We study the effective operators of the standard model fields which would yield an observable rate of neutrinoless double beta decay. We particularly focus on the possibility that neutrinoless double beta decay is dominantly induced by lepton-number-violating higher dimensional operators other than the Majorana neutrino mass. Our analysis can be applied to models in which neutrinoless double beta decay is induced either by strong dynamics or by quantum gravity effects at a fundamental scale near the TeV scale as well as the conventional models in which neutrinoless double beta decay is induced by perturbative renormalizable interactions.

If the fundamental Planck scale is near a TeV, then parton collisions with high enough center-of-mass energy should produce black holes. The production rate for such black holes at the CERN LHC has been extensively studied for the case of a proton-proton collision. In this paper, we extend this analysis to a lead-lead collision at LHC. We find that the cross section for small black holes which may in principle be produced in such a collision is either enhanced or suppressed, depending upon the black hole mass. For example, for black holes with a mass around 3 TeV we find that the differential black hole production cross section, $d\sigma /dM,$ in a typical lead-lead collision is up to 90 times larger than that for black holes produced in a typical proton-proton collision. We also discuss the cross sections for “string ball” production in these collisions. For string balls of mass about 1 (2) TeV, we find that the differential production cross section in a typical lead-lead collision may be enhanced by a factor up to 3300 (850) times that of a proton-proton collision at LHC.

We consider flat solutions in a brane world model with a massless scalar field appearing in 5D $H_{\mathrm{MNPQ}}^2.$ Since those solutions have naked bulk singularities or are such that the 4D Planck mass is divergent, we should have a compact extra dimension, the size of which is then fixed by brane tension(s) and the bulk cosmological constant. By inspecting scalar perturbations around the flat solutions, we find that there is no zero mode for the radion and radion modes have only positive masses. This result confirms the fact that the radius of the extra dimension cannot be adjusted independently of the parameters of the model, and thus that the model considered does not solve the problems encountered in other approaches to the self-tuning of the cosmological constant.

We show that the high temperature behavior of noncommutative QED may be simply obtained from Boltzmann transport equations for classical particles. The transport equation for the charge neutral particle is shown to be characteristically different from that for the charged particle. These equations correctly generate, for arbitrary values of the noncommutative parameter $\theta ,$ the leading, gauge independent hard thermal loops, arising from the fermion and the gauge sectors. We briefly discuss the generating functional of hard thermal amplitudes.

By using an isotropic field configuration for the triplet ansatz sector of the metric-affine theories of gravity (MAG), we find a class of harmonic solutions which represents the interior and exterior field of a distribution endowed with electric and strong gravitoelectric multipole moments. Moreover, the general matching and junction conditions in MAG and their reduction to the triplet ansatz sector are presented.

The stability of the Cauchy horizon in spherically symmetric self-similar collapse is studied by determining the flux of scalar radiation impinging on the horizon. This flux is found to be finite.

This article investigates the generation of non-Gaussianity during inflation. In the context of multifield inflation, we detail a mechanism that can create significant primordial non-Gaussianities in the adiabatic mode while preserving the scale invariance of the power spectrum. This mechanism is based on the generation of non-Gaussian isocurvature fluctuations which are then transferred to the adiabatic modes through a bend in the classical inflaton trajectory. Natural realizations involve quartic self-interaction terms for which a full computation can be performed. The expected statistical properties of the resulting metric fluctuations are shown to be the superposition of a Gaussian and a non-Gaussian contribution of the same variance. The relative weight of these two contributions is related to the total bending in field space. We explicit the non-Gaussian probability distribution function which appears to be described by a single new parameter. Only two new parameters therefore suffice in describing the non-Gaussianity.

We calculate the string tension and part of the mass spectrum of SU(4) and SU(6) gauge theories in 2+1 dimensions using lattice techniques. We combine these new results with older results for $N_c=2,\dots ,5\mathrm{}$ so as to obtain more accurate extrapolations to $N_c=\infty .$ The qualitative conclusions of the earlier work are unchanged: $\mathrm{SU}{(N}_c)$ theories in 2+1 dimensions are linearly confining as $N_c\to \infty ;$ the limit is achieved by keeping $g^2{N}_c$ fixed; SU(3), and even SU(2), are “close” to $\mathrm{SU}\left(\infty \right).\mathrm{}$ We obtain more convincing evidence than before that the leading large-$N_c$ correction is ${O(1/N}_c^2).\mathrm{}$ We look for the multiplication of states that one expects in simple flux loop models of glueballs, but find no evidence for this.

We investigate the consequences of enforcing local color neutrality on the color superconducting phases of quark matter by utilizing the Nambu–Jona-Lasinio model supplemented by diquark and the ’t Hooft six-fermion interactions. In neutrino free matter at zero temperature, color neutrality guarantees that the number densities of u, d, and s quarks in the color-flavor-locked (CFL) phase will be equal even with physical current quark masses. Electric charge neutrality follows as a consequence and without the presence of electrons. In contrast, electric charge neutrality in the less symmetric 2-flavor superconducting (2SC) phase with $\mathrm{ud}$ pairing requires more electrons than the normal quark phase. The free energy density cost of enforcing color and electric charge neutrality in the CFL phase is lower than that in the 2SC phase, which favors the formation of the CFL phase. With increasing temperature and neutrino content, an unlocking transition occurs from the CFL phase to the 2SC phase with the order of the transition depending on the temperature, the quark and lepton number chemical potentials. The astrophysical implications of this rich structure in the phase diagram, including estimates of the effects from Goldstone bosons in the CFL phase, are discussed.

We consider a hydrogen atom in the background spacetimes generated by an infinitely thin cosmic string and by a pointlike global monopole. In both cases, we find the solutions of the corresponding Dirac equations and we determine the energy levels of the atom. We investigate how the geometric and topological features of these spacetimes lead to shifts in the energy levels as compared with the flat Minkowski spacetime.

We show that the increase of the generalized entropy by a quantum process outside the horizon of a black hole is more than the Holevo bound of the classical information which could be obtained by further observations outside the horizon. In the optimal case, the prepared information can be completely retrieved.

We consider gravity mediated supersymmetry (SUSY) breaking in 5D spacetime with two 4D branes B1 and B2 separated in the extra dimension. Using an off-shell 5D supergravity (SUGRA) formalism, we argue that the SUSY breaking scales could be nonuniversal even at the fundamental scale in a brane world setting, since SUSY breaking effects could be effectively localized. As an application, we suggest a model in which the two light chiral minimal supersymmetric standard model generations reside on B1, while the third generation is located on B2, and the Higgs multiplets as well as gravity and gauge multiplets reside in the bulk. For SUSY breaking of the order of 10–20 TeV caused by a hidden sector localized at B1, the scalars belonging to the first two generations can become sufficiently heavy to overcome the SUSY flavor problem. SUSY breaking on B2 from a different localized hidden sector gives rise to the third generation soft scalar masses of the order of 1 TeV. Gaugino masses are also of the order of 1 TeV if the size of the extra dimension is $\sim {10}^{-16}{\mathrm{GeV}}^{-1}.$ As in 4D effective supersymmetric theory, an adjustment of TeV scale parameters is needed to realize the 100 GeV electroweak symmetry breaking scale.

We investigate in detail the $A^0{Z}^0$ associated production process $p\overrightarrow{p}{A}^0{Z}^0+X$ within the framework of the minimal supersymmetric standard model (MSSM) at the CERN Large Hadron Collider (LHC), considering contributions from both the Drell-Yan and gluon fusion subprocesses. We focus on the deviations from the general two-Higgs-doublet model (2HDM) arising in the MSSM. We also discuss the contributions of the two $A^0{Z}^0$ associated production subprocesses in the MSSM at the CERN LHC and analyze the dependences of the total cross section on neutral $\mathrm{CP}$-odd Higgs boson mass $m_A$ and $\tan \beta$ in the MSUGRA scenario. We find that the contribution from the loop mediated gluon fusion subprocess can be competitive with that from the Drell-Yan subprocess in some parameter space.

Recent neutrino data have been favorable to a nearly bimaximal mixing, which suggests a simple form of the neutrino mass matrix. Stimulated by this matrix form, the possibility that all the mass matrices of quarks and leptons have the same form as in neutrinos is investigated. The mass matrix form is constrained by a discrete symmetry ${\mathrm{Z}}_3$ and a permutation symmetry ${\mathrm{S}}_2.$ The model, of course, leads to a nearly bimaximal mixing for the lepton sectors, while, for the quark sectors, it can lead to reasonable values of the CKM mixing matrix and masses.

We consider the stability of the two branches of nonextremal enhançon solutions. We argue that one would expect a transition between the two branches at some value of the nonextremality, which should manifest itself in some instability. We study small perturbations of these solutions, constructing a sufficiently general ansatz for linearized perturbations of the nonextremal solutions, and show that the linearized equations are consistent. We show that the simplest kind of perturbation does not lead to any instability. We reduce the problem of studying the more general spherically symmetric perturbation to solving a set of three coupled second-order differential equations.

The nullification of threshold amplitudes is considered within the conventional framework of quantum field theory. The relevant Ward identities for the reduced theory are derived both on path-integral and diagrammatic levels. They are then used to prove the vanishing of tree-graph threshold amplitudes.

Cosmic microwave background (CMB) observations provide in principle a high-precision test of models which are motivated by M theory. We set out the framework of a program to compute the tensor anisotropies in the CMB that are generated in braneworld models. In the simplest approximation, we show the braneworld imprint as a correction to the power spectra for standard temperature and polarization anisotropies.

A nonlinear wave interaction of low amplitude gravitational waves in flat space-time is considered. An analogy with optics is established. It is shown that the flat metric space-time is equivalent to a centrosymmetric optical medium, with no second order susceptibility. The lowest order nonlinear effects are those due to the third order nonlinearity and include self-phase modulation and high harmonic generation. These processes lead to an efficient energy dilution of the gravitational wave energy over an increasingly large spectral range.

Turbulence may have been produced in the early universe by several nonequilibrium processes. Periods of cosmic turbulence may have left a detectable relic under the form of stochastic backgrounds of gravitational waves. In this paper we derive general expressions for the power spectrum of the expected signal. Extending previous works on the subject, we take into account the effects of a continuous energy injection power and of magnetic fields. Both effects lead to relevant deviations from the Kolmogoroff turbulence spectrum. We apply our results to determine the spectrum of gravity waves which may have been produced by neutrino inhomogeneous diffusion and during a first order phase transition. We show that in both cases the expected signal may be in the sensitivity range of the interferometer LISA.