We propose the minimal supersymmetric sterile neutrino model (MSSNM) where the sterile neutrino masses are about 1 eV, while the active neutrino masses and the mixings among the active and sterile neutrinos are generated during late time phase transition. All the current experimental neutrino data include the LSND can be explained simultaneously, and the constraints on the sterile neutrinos from the big bang nucleosynthesis and large scale structure can be evaded. To realize the MSSNM naturally, we consider the supersymmetric intermediate-scale $U(1{)}^{\prime }$ model, the low-energy $U(1{)}^{\prime }$ model with a secluded $U(1{)}^{\prime }$-breaking sector, and the DFSZ and KSVZ axion models. In these models, the $\mu$ problem can be solved elegantly, and the 1 eV sterile neutrino masses can be generated via high-dimensional operators. For the low-energy $U(1{)}^{\prime }$ model with a secluded $U(1{)}^{\prime }$-breaking sector, we also present a scenario in which the masses and mixings for the active and sterile neutrinos are all generated during late time phase transition.

Fat link irrelevant clover (FLIC) overlap fermions are a variant of the standard (Wilson) overlap action, with the FLIC action as the overlap kernel rather than the Wilson action. The structure of the FLIC overlap fermion propagator in momentum space is studied, and a comparison against previous studies of the Wilson overlap propagator in quenched QCD is performed. To explore the scaling properties of the propagator for the two actions, numerical calculations are performed in Landau gauge across three lattices with different lattice spacing $a$ and similar physical volumes. We find that at light quark masses the actions agree in both the infrared and the ultraviolet, but at heavier masses some disagreement in the ultraviolet appears. This is attributed to the two actions having different discretisation errors with the FLIC overlap providing superior performance in this regime. Both actions scale reasonably, but some scaling violations are observed.

Measurements by Belle Collaboration of the cross section for inclusive $J/\psi$ production in $e^{+}{e}^{-}$ annihilation have been a serious challenge to current heavy-quarkonium theory. In particular, the measured cross sections for exclusive $J/\psi +{\eta }_c$ and inclusive $J/\psi +c\overline{c}+X$ differ from nonrelativistic QCD predictions by an order of magnitude. In order to check if other available alternative theories can resolve such a large discrepancy, we calculate the cross section for inclusive $J/\psi +c\overline{c}+X$ based on the color-evaporation model. As a phenomenological model, the color-evaporation model is still employed to predict cross sections for inclusive quarkonium production in various processes. Our results show that the color-evaporation-model prediction is even smaller than the nonrelativistic QCD prediction by an order of magnitude. The resultant color-evaporation-model prediction for the $J/\psi +c\overline{c}+X$ fraction in the inclusive $J/\psi$ production cross section is 0.049, while the empirical value measured by Belle Collaboration is 0.82.

We investigate the sea quark polarization in the nucleon by means of a combined next to leading order analysis to the recently enlarged set of inclusive and semi-inclusive polarized deep inelastic scattering data. Using the Lagrange multiplier method, we assess the uncertainty inherent to the extraction of the different spin-dependent parton densities in a QCD global fit and the impact of the increased set of semi-inclusive data now available. We comment on future prospects at Relativistic Heavy Ion Collider and the Thomas Jefferson National Laboratory and their potential impact in the future determination of polarized parton densities.

The scale of mass generation for fermions (including neutrinos) and the scale for electroweak symmetry breaking (EWSB) can be bounded from above by the unitarity of scattering involving longitudinal weak gauge bosons or their corresponding would-be Goldstone bosons. Including the exact $n$-body phase space we analyze the $2\to n$ ($n\ge 2$) processes for the fermion-(anti)fermion scattering into multiple gauge boson final states. Contrary to naïve energy power counting, we demonstrate that as $n$ becomes large, the competition between an increasing energy factor and a phase-space suppression leads to a strong new upper bound on the scale of fermion mass generation at a finite value $n=n_s$, which is independent of the EWSB scale, $v=(\sqrt{2}{G}_F{)}^{-1/2}$. For quarks, leptons, and Majorana neutrinos, the strongest $2\to n$ limits range from about 3 TeV to 130–170 TeV (with $2\lesssim n_s\lesssim 24$), depending on the measured fermion masses. Strikingly, given the tiny neutrino masses as constrained by the neutrino oscillations, neutrinoless double-beta decays and astrophysical observations, the unitarity violation of ${\nu }_L{\nu }_L\to n{W}_L^a$ scattering actually occurs at a scale no higher than $\sim 170\mathrm{TeV}$. Implications for various mechanisms of neutrino mass generation are analyzed. On the other hand, for the $2\to n$ pure Goldstone boson scattering, we find that the decreasing phase-space factor always dominates over the growing overall energy factor when $n$ becomes large, so that the best unitarity bound on the scale of EWSB remains at $n=2$.

We consider a large number of pair production processes at future colliders (LHC, ILC) for values of the c.m. energy in the TeV range, where a logarithmic expansion of Sudakov kind would provide a reliable description of split supersymmetric electroweak effects. We calculate all the leading and next-to-leading terms of the expansions, that would differ drastically in the considered domain from those of an extreme light scenario. We imagine then two possible competitive future situations, at LHC and at ILC, where the determination of the energy dependence of the cross sections of certain processes could reveal a “signal” of the correct supersymmetric scheme.

We report the results of a search for the decay modes $B^0\to J/\psi {\overline{D}}^0$ and $B^{+}\to J/\psi {\overline{D}}^0{\pi }^{+}$. The analysis is based on $140\mathrm{f}{\mathrm{b}}^{-1}$ of data accumulated by the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider. No significant signals are observed and we determine the branching fraction upper limits $\mathcal{B}(B^0\to J/\psi {\overline{D}}^0)<2.0\times {10}^{-5}$ and $\mathcal{B}(B^{+}\to J/\psi {\overline{D}}^0{\pi }^{+})<2.5\times {10}^{-5}$ at $90\%$ confidence level. These results rule out the explanation of the excess in the low momentum region of the inclusive $J/\psi$ spectrum as intrinsic charm content in the $B$ meson. The branching fractions of the corresponding nonresonant decay channels are also reported.

We report measurements of $B$ to pseudoscalar-pseudoscalar decays with at least one $\eta$ meson in the final state using $140{\mathrm{fb}}^{-1}$ of data collected by the Belle detector at KEKB $e^{+}{e}^{-}$ collider. We observe the decay $B^{+}\to \eta {\pi }^{+}$ and find evidence of $B^{+}\to \eta K^{+}$; the measured branching fractions are $\mathcal{B}(B^{+}\to \eta {\pi }^{+})=({4.8}_{-0.7}^{+0.8}(\mathrm{stat})\pm 0.3(\mathrm{sys}))\times {10}^{-6}$ and $\mathcal{B}(B^{+}\to \eta K^{+})=(2.1\pm 0.6(\mathrm{stat})\pm 0.2(\mathrm{sys}))\times {10}^{-6}$. Their corresponding $CP$ violating asymmetries are measured to be $0.07\pm 0.15(\mathrm{stat})\pm 0.03(\mathrm{sys})$ for $\eta {\pi }^{\pm }$ and $-0.49\pm 0.31(\mathrm{stat})\pm 0.07(\mathrm{sys})$ for $\eta K^{\pm }$. No significant signals are found for neutral $B\to \eta h$ decays. We report the following upper limits on branching fractions at the $90\%$ confidence level: $\mathcal{B}(B^0\to \eta K^0)<2.0\times {10}^{-6},\mathcal{B}(B^0\to \eta {\pi }^0)<2.5\times {10}^{-6}$ and $\mathcal{B}(B^0\to \eta \eta )<2.0\times {10}^{-6}$.

The study of new Bogomol’nyi-Prasad-Sommerfield (BPS) objects in ${\mathrm{AdS}}_5$ has led to a deeper understanding of AdS/CFT. To help complete this picture, and to fully explore the consequences of the supersymmetry algebra, it is also important to obtain new solutions with bulk fermions turned on. In this paper we construct superpartners of the $1/2$ BPS black hole in ${\mathrm{AdS}}_5$ using a natural set of fermion zero modes. We demonstrate that these superpartners, carrying fermionic hair, have conserved charges differing from the original bosonic counterpart. To do so, we find the $R$-charge and dipole moment of the new system, as well as the mass and angular momentum, defined through the boundary stress tensor. The complete set of superpartners fits nicely into a chiral representation of ${\mathrm{AdS}}_5$ supersymmetry, and the spinning solutions have the expected gyromagnetic ratio, $g=1$.

We investigate formation of an apparent horizon (AH) in high-energy particle collisions in four- and higher-dimensional general relativity, motivated by TeV-scale gravity scenarios. The goal is to estimate the prefactor in the geometric cross section formula for the black hole production. We numerically construct AHs on the future light cone of the collision plane. Since this slice lies to the future of the slice used previously by Eardley and Giddings [Phys. Rev. D 66, 044011 (2002)] and by one of us and Nambu [Phys. Rev. D 67, 024009 (2003)], we are able to improve the prefactor estimates. The black hole production cross section increases by 40%–70% in the higher-dimensional cases, indicating larger black hole production rates in future-planned accelerators than previously estimated. We also determine the mass and the angular momentum of the final black hole state, as allowed by the area theorem.

We study exact stationary and axisymmetric solutions describing charged rotating black holes localized on a 3-brane in the Randall-Sundrum braneworld. The charges of the black holes are considered to be of two types, the first being an induced tidal charge that appears as an imprint of nonlocal gravitational effects from the bulk space and the second is a usual electric charge arising due to a Maxwell field trapped on the brane. We assume a special ansatz for the metric on the brane taking it to be of the Kerr-Schild form and show that the Kerr-Newman solution of ordinary general relativity in which the electric charge is superseded by a tidal charge satisfies a closed system of the effective gravitational field equations on the brane. It turns out that the negative tidal charge may provide a mechanism for spinning up the black hole so that its rotation parameter exceeds its mass. This is not allowed in the framework of general relativity. We also find a new solution that represents a rotating black hole on the brane carrying both charges. We show that for a rapid enough rotation the combined influence of the rotational dynamics and the local bulk effects of the “squared” energy-momentum tensor on the brane distort the horizon structure of the black hole in such a way that it can be thought of as composed of nonuniformly rotating null circles with growing radii from the equatorial plane to the poles. We finally study the geodesic motion of test particles in the equatorial plane of a rotating black hole with tidal charge. We show that the effects of negative tidal charge tend to increase the horizon radius, as well as the radii of the limiting photon orbit, the innermost bound and the innermost stable circular orbits for both direct and retrograde motions of the particles.

We compute the regularized force density and renormalized action due to fields of external origin coupled to a brane of arbitrary dimension in a spacetime of any dimension. Specifically, we consider forces generated by gravitational, dilatonic, and generalized antisymmetric form-fields. The force density is regularized using a recently developed gradient operator. For the case of a Nambu-Goto brane, we show that the regularization leads to a renormalization of the tension, which is seen to be the same in both approaches. We discuss the specific couplings which lead to cancellation of the self-force in this case.

We use cosmic microwave background data from WMAP, ACBAR, VSA and CBI, and galaxy power spectrum data from 2dF, to constrain flat cosmologies based on the Jordan-Brans-Dicke theory, using a Markov chain Monte Carlo approach. Using a parametrization based on $\xi =1/4\omega$, and performing an exploration in the range $\ln \xi \in [-9,3]$, we obtain a 95% marginalized probability bound of $\ln \xi <-6.2$, corresponding to a 95% marginalized probability lower bound on the Brans-Dicke parameter $\omega >120$.

Reductions from odd to even dimensionalities ($5\to 4$ or $3\to 2$), for which the effective low-energy theory contains chiral fermions, present us with a mismatch between ultraviolet and infrared anomalies. This applies to both local (gauge) and global currents; here we consider the latter case. We show that the mismatch can be explained by taking into account a change in the spectral asymmetry of the massive modes—an odd-dimensional analog of the phenomenon described by the Atiyah-Patodi-Singer theorem in even dimensionalities. The result has phenomenological implications: we present a scenario in which a QCD-like $\theta$-angle relaxes to zero on a certain (possibly, cosmological) time scale, despite the absence of any light axionlike particle.

The bubble nucleation rate for a first order phase transition occurring on a brane world is calculated. Both the Coleman-de Luccia thin wall instanton and the Hawking-Moss instanton are considered. The results are compared with the corresponding nucleation rates for standard four-dimensional gravity.

We present exact solutions of the gravitational field equations in the generalized Randall-Sundrum model for an anisotropic brane with Bianchi type I geometry, with a generalized Chaplygin gas as matter source. The generalized Chaplygin gas, which interpolates between a high density relativistic era and a nonrelativistic matter phase, is a popular dark energy candidate. For a Bianchi type I space-time brane filled with a cosmological fluid obeying the generalized Chaplygin equation of state the general solution of the gravitational field equations can be expressed in an exact parametric form, with the comoving volume taken as parameter. In the limiting cases of a stiff cosmological fluid, with pressure equal to the energy density, and for a pressureless fluid, the solution of the field equations can be expressed in an exact analytical form. The evolution of the scalar field associated to the Chaplygin fluid is also considered and the corresponding potential is obtained. The behavior of the observationally important parameters like shear, anisotropy, and deceleration parameter is considered in detail.

We propose a model of cosmology and particle physics in which all relevant scales arise in a natural way from an intermediate string scale. We are led to assign the string scale to the intermediate scale $M_{*}\sim {10}^{13}\mathrm{GeV}$ by four independent pieces of physics: electroweak symmetry breaking; the $\mu$ parameter; the axion scale; and the neutrino mass scale. The model involves hybrid inflation with the waterfall field $N$ being responsible for generating the $\mu$ term, the right-handed neutrino mass scale, and the Peccei-Quinn symmetry breaking scale. The large scale structure of the Universe is generated by the lightest right-handed sneutrino playing the rôle of a coupled curvaton. We show that the correct curvature perturbations may be successfully generated providing the lightest right-handed neutrino is weakly coupled in the seesaw mechanism, consistent with sequential dominance.

During the last ten years a detailed investigation of preheating was performed for chaotic inflation and for hybrid inflation. However, nonperturbative effects during reheating in the new inflation scenario remained practically unexplored. We investigate preheating in new inflation, using a combination of analytical and numerical methods. We find that the decay of the homogeneous component of the inflaton field and the resulting process of spontaneous symmetry breaking in the simplest models of new inflation usually occurs almost instantly: for the new inflation on the GUT scale it takes only about 5 oscillations of the field distribution. The decay of the homogeneous inflaton field is so efficient because of a combined effect of tachyonic preheating and parametric resonance. At that stage, the homogeneous oscillating inflaton field decays into a collection of waves of the inflaton field, with a typical wavelength of the order of the inverse inflaton mass. This stage usually is followed by a long stage of decay of the inflaton field into other particles, which can be described by the perturbative approach to reheating after inflation. The resulting reheating temperature typically is rather low.

We combine the constraints from the recent Ly$\alpha$ forest analysis of the Sloan Digital Sky Survey (SDSS) and the SDSS galaxy bias analysis with previous constraints from SDSS galaxy clustering, the latest supernovae, and 1st year WMAP cosmic microwave background anisotropies. We find significant improvements on all of the cosmological parameters compared to previous constraints, which highlights the importance of combining Ly$\alpha$ forest constraints with other probes. Combining WMAP and the Ly$\alpha$ forest we find for the primordial slope $n_s=0.98\pm 0.02$. We see no evidence of running, $dn/d\ln k=-0.003\pm 0.010$, a factor of $3$ improvement over previous constraints. We also find no evidence of tensors, $r<0.36$ ($95\%$ c.l.). Inflationary models predict the absence of running and many among them satisfy these constraints, particularly negative curvature models such as those based on spontaneous symmetry breaking. A positive correlation between tensors and primordial slope disfavors chaotic inflation-type models with steep slopes: while the $V\propto {\varphi }^2$ model is within the 2-sigma contour, $V\propto {\varphi }^4$ is outside the 3-sigma contour. For the amplitude we find ${\sigma }_8=0.90\pm 0.03$ from the Ly$\alpha$ forest and WMAP alone. We find no evidence of neutrino mass: for the case of $3$ massive neutrino families with an inflationary prior, $\sum _{}^{}{m}_{\nu }<0.42$ eV and the mass of lightest neutrino is $m_1<0.13$ eV at $95\%$ c.l. For the 3 massless $+1$ massive neutrino case we find $m_{\nu }<0.79$ eV for the massive neutrino, excluding at $95\%$ c.l. all neutrino mass solutions compatible with the LSND results. We explore dark energy constraints in models with a fairly general time dependence of dark energy equation of state, finding ${\Omega }_{\lambda }=0.72\pm 0.02$, $\mathrm{w}(z=0.3)=-{0.98}_{-0.12}^{+0.10}$, the latter changing to $\mathrm{w}(z=0.3)=-{0.92}_{-0.10}^{+0.09}$ if tensors are allowed. We find no evidence for variation of the equation of state with redshift, $\mathrm{w}(z=1)=-{1.03}_{-0.28}^{+0.21}$. These results rely on the current understanding of the Ly$\alpha$ forest and other probes, which need to be explored further both observationally and theoretically, but extensive tests reveal no evidence of inconsistency among different data sets used here.

We present a method for measuring the cosmic expansion history $H(z)$ in uncorrelated redshift bins, and apply it to current and simulated type Ia supernova data assuming spatial flatness. If the matter density parameter ${\Omega }_m$ can be accurately measured from other data, then the dark-energy density history $X(z)={\rho }_X(z)/{\rho }_X(0)$ can trivially be derived from this expansion history $H(z)$. In contrast to customary “black box” parameter fitting, our method is transparent and easy to interpret: the measurement of $H(z{)}^{-1}$ in a redshift bin is simply a linear combination of the measured comoving distances for supernovae in that bin, making it obvious how systematic errors propagate from input to output. We find the Riess et al. (2004) gold sample to be consistent with the vanilla concordance model where the dark energy is a cosmological constant. We compare two mission concepts for the NASA/DOE Joint Dark-Energy Mission (JDEM), the Joint Efficient Dark-energy Investigation (JEDI), and the Supernova Accelaration Probe (SNAP), using simulated data including the effect of weak lensing (based on numerical simulations) and a systematic bias from K corrections. Estimating $H(z)$ in seven uncorrelated redshift bins, we find that both provide dramatic improvements over current data: JEDI can measure $H(z)$ to about 10% accuracy and SNAP to 30%–40% accuracy.