A wave impinging on a Kerr black hole can be amplified as it scatters off the hole if certain conditions are satisfied, giving rise to superradiant scattering. By placing a mirror around the black hole one can make the system unstable. This is the black-hole bomb of Press and Teukolsky. We investigate in detail this process and compute the growing time scales and oscillation frequencies as a function of the mirror’s location. It is found that in order for the system black hole plus mirror to become unstable there is a minimum distance at which the mirror must be located. We also give an explicit example showing that such a bomb can be built. In addition, our arguments enable us to justify why large Kerr-AdS black holes are stable and small Kerr-AdS black holes should be unstable.

We study, analytically and with lattice simulations, the decay of coherent field oscillations and the subsequent thermalization of the resulting stochastic classical wave field. The problem of reheating of the Universe after inflation constitutes our prime motivation and application of the results. We identify three different stages of these processes. During the initial stage of “parametric resonance,” only a small fraction of the initial inflaton energy is transferred to fluctuations in the physically relevant case of sufficiently large couplings. A major fraction is transferred in the prompt regime of driven turbulence. The subsequent long stage of thermalization classifies as free turbulence. During the turbulent stages, the evolution of particle distribution functions is self-similar. We show that wave kinetic theory successfully describes the late stages of our lattice calculation. Our analytical results are general and give estimates of reheating time and temperature in terms of coupling constants and initial inflaton amplitude.

We examine the possibility that galactic halos are collisionless ensembles of scalar field “massive compact halo objects” (MACHOs). Using mass constraints from MACHO microlensing and from theoretical arguments on halos made up of massive black holes, as well as demanding also that scalar MACHO ensembles of all scales do not exhibit gravothermal instability (as required by consistency with observations of LSB galaxies), we obtain the range: $m\lesssim {10}^{-7}{M}_{\odot }$ or ${30M}_{\odot }\lesssim m\lesssim {100M}_{\odot }.$ The rather narrow mass range of large MACHOs seems to indicate that the ensembles we are suggesting should be probably made up of scalar MACHOs in the low mass range (“mini-MACHOs”). The proposed model allows one to consider a nonbaryonic and nonthermal fundamental nature of dark matter, while at the same time keeping the same phenomenology of the CDM paradigm.

We investigate a string-inspired scenario associated with a rolling massive scalar field on D-branes and discuss its cosmological implications. In particular, we discuss cosmological evolution of the massive scalar field on the anti-D3 brane of KKLT vacua. Unlike the case of tachyon field, because of the warp factor of the anti-D3 brane, it is possible to obtain the required level of the amplitude of density perturbations. We study the spectra of scalar and tensor perturbations generated during the rolling scalar inflation and show that our scenario satisfies the observational constraint coming from the cosmic microwave background anisotropies and other observational data. We also implement the negative cosmological constant arising from the stabilization of the modulus fields in the KKLT vacua and find that this leads to a successful reheating in which the energy density of the scalar field effectively scales as a pressureless dust. The present dark energy can be also explained in our scenario provided that the potential energy of the massive rolling scalar does not exactly cancel with the amplitude of the negative cosmological constant at the potential minimum.

Deep multicolor galaxy surveys with photometric redshifts will provide a large number of two-point correlation observables: galaxy-galaxy angular correlations, galaxy-shear cross correlations, and shear-shear correlations between all redshifts. These observables can potentially enable a joint determination of the dark-energy-dependent evolution of the dark matter and distances as well as the relationship between galaxies and dark matter halos. With recent cosmic microwave background determinations of the initial power spectrum, a measurement of the mass clustering at even a single redshift will constrain a well-specified combination of dark energy (DE) parameters in a flat universe; we provide convenient fitting formulas for such studies. The combination of galaxy-shear and galaxy-galaxy correlations can determine this amplitude at multiple redshifts. We illustrate this ability in a description of the galaxy clustering with 5 free functions of redshift which can be fitted from the data. The galaxy modeling is based on a mapping onto halos of the same abundance that models a flux-limited selection. In this context and under a flat geometry, a 4000 deg${}^2$ galaxy-lensing survey can achieve a statistical precision of $\sigma \left({\Omega }_{\mathrm{DE}}\right)=0.005\mathrm{}$ for the dark energy density, $\sigma {(w}_{\mathrm{DE}})=0.02\mathrm{}$ and $\sigma {(w}_a)=0.17\mathrm{}$ for its equation of state and evolution, evaluated at dark energy matter equality $z\approx 0.4,$ as well as constraints on the 5 halo functions out to $z=1.\mathrm{}$ More importantly, a joint analysis can make dark energy constraints robust against systematic errors in the shear-shear correlation and halo modeling.

We have revised the calculation of the flux of atmospheric neutrinos based on a three-dimensional scheme with the realistic IGRF geomagnetic model. The primary flux model has been revised, based on the AMS and BESS observations, and the interaction model updated to DPMJET-III. With a fast simulation code and computer system, the statistical errors in the Monte Carlo study are negligible. We estimate the total uncertainty of the atmospheric neutrino flux prediction is reduced to $\lesssim 10\%$ below 10 GeV. The “three-dimensional effects” are found to be almost the same as the study with the dipole magnetic field, but the muon-curvature effect remains up to a few tens of GeV for horizontal directions. The uncertainty of the absolute normalization of the atmospheric neutrino is still large, above 10 GeV, due to the uncertainty of the primary cosmic ray flux above 100 GeV. However, the zenith angle variation is not affected by these uncertainties.

Motivated by a variety of theories that predict new effects, we tested the gravitational ${1/r}^2$ law at separations between 10.77 mm and $137\mu \mathrm{m}$ using two different 10-fold azimuthally symmetric torsion pendulums and rotating 10-fold symmetric attractors. Our work improves upon other experiments by up to a factor of about 100. We found no deviation from Newtonian physics at the 95% confidence level and interpret these results as constraints on extensions of the standard model that predict Yukawa or power-law forces. We set a constraint on the largest single extra dimension (assuming toroidal compactification and that one extra dimension is significantly larger than all the others) of $R_{*}<~160\mu \mathrm{m},$ and on two equal-sized large extra dimensions of $R_{*}<~130\mu \mathrm{m}.$ Yukawa interactions with $|\alpha |>~1$ are ruled out at 95% confidence for $\lambda >~197\mu \mathrm{m}.$ Extra-dimensions scenarios stabilized by radions are restricted to unification masses $M_{*}>~3.0\mathrm{TeV}{/c}^2,$ regardless of the number of large extra dimensions. We also provide new constraints on power-law potentials $V\left(r\right)\mathrm{}\propto r^{-k}$ with k between 2 and 5 and on the ${\gamma }_5$ couplings of pseudoscalars with $m<~10\mathrm{meV}{/c}^2.$

Japanese laser interferometric gravitational wave detectors, TAMA300 and LISM, performed a coincident observation during 2001. We perform a coincidence analysis to search for inspiraling compact binaries. The length of data used for the coincidence analysis is 275 hours when both TAMA300 and LISM detectors are operated simultaneously. TAMA300 and LISM data are analyzed by matched filtering, and candidates for gravitational wave events are obtained. If there is a true gravitational wave signal, it should appear in both data of detectors with consistent waveforms characterized by masses of stars, amplitude of the signal, the coalescence time and so on. We introduce a set of coincidence conditions of the parameters, and search for coincident events. This procedure reduces the number of fake events considerably, by a factor $\sim {10}^{-4}$ compared with the number of fake events in single detector analysis. We find that the number of events after imposing the coincidence conditions is consistent with the number of accidental coincidences produced purely by noise. We thus find no evidence of gravitational wave signals. We obtain an upper limit of 0.046 [1/h] $(\mathrm{C}.\mathrm{L}.\mathrm{}=90\%)$ to the galactic event rate within 1 kpc from the Earth. The method used in this paper can be applied straightforwardly to the case of coincidence observations with more than two detectors with arbitrary arm directions.

We revisit the calculation of the abundance of primordial black holes (PBHs) formed from primordial density perturbations, using a formation criterion derived by Shibata and Sasaki which refers to a metric perturbation variable rather than the usual density contrast. We implement a derivation of the PBH abundance which uses peaks theory, and compare it to the standard calculation based on a Press-Schechter-like approach. We find that the two are in reasonable agreement if the Press-Schechter threshold is in the range ${\Delta }_{\mathrm{th}}\simeq 0.3$ to 0.5, but advocate use of the peaks theory expression which is based on a sounder theoretical footing.

Applying thermal renormalization group (TRG) equations to ${\phi }^4$ theory with spontaneous breaking symmetry, we investigate the critical behavior of the damping rate for the plasmons with finite momentum at the symmetry-restoring phase transition. From the TRG equation the IR cutoff provided by the external momentum leads to that the momentum-dependent coupling constant stops running in the critical region. As a result, the critical slowing down phenomenon reflecting the inherently IR effect does not take place at the critical point for the plasmon with finite external momentum.

Minimal $S_3$ invariant Higgs potential with real soft $S_3$ breaking masses is investigated. It is required that without having a problem with triviality, all physical Higgs bosons, except one neutral one, become heavy $\gtrsim 10\mathrm{TeV}$ in order to sufficiently suppress flavor-changing neutral currents. There exist three nonequivalent soft mass terms that can be characterized according to their discrete symmetries, and the one that breaks $S_3$ completely. The $S_2^{\prime }$ invariant vacuum expectation values (VEVs) of the Higgs fields are the most economic VEVs in the sense that the freedom of VEVs can be completely absorbed into the Yukawa couplings so that it is possible to derive, without referring to the details of the VEVs, the most general form for the fermion mass matrices in minimal $S_3$ extension of the standard model. We find that except for the completely broken case of the soft terms, the $S_2^{\prime }$ invariant VEVs are unique VEVs that satisfy the requirement of heavy Higgs bosons. It is found that they also correspond to a local minimum in the completely broken case.

We construct a family-unified model on a $Z_2\times Z_2$ orbifold in five dimensions. The model is based on a supersymmetric $\mathrm{SU}\left(7\right)\mathrm{}$ gauge theory. The gauge group is broken by orbifold boundary conditions to a product of grand unified $\mathrm{SU}\left(5\right)\mathrm{}$ and $\mathrm{SU}\left(2\right)\mathrm{}\times U\left(1\right)\mathrm{}$ flavor symmetry. The structure of Yukawa matrices is generated by an interplay between spontaneous breaking of flavor symmetry and geometric factors arising due to field localization in the extra dimension.

We study effects of supersymmetric particles in various rare B decay processes as well as in the unitarity triangle analysis. We consider three different supersymmetric models, the minimal supergravity, $\mathrm{SU}\left(5\right)\mathrm{}$ SUSY GUT with right-handed neutrinos, and the minimal supersymmetric standard model with $U\left(2\right)\mathrm{}$ flavor symmetry. In the $\mathrm{SU}\left(5\right)\mathrm{}$ SUSY GUT with right-handed neutrinos, we consider two cases of the mass matrix of the right-handed neutrinos. We calculate direct and mixing-induced CP asymmetries in the $\overrightarrow{b}s\gamma$ decay and CP asymmetry in $B_d\to \phi K_S$ as well as the $B_s–B_s$ mixing amplitude for the unitarity triangle analysis in these models. We show that large deviations are possible for the $\mathrm{SU}\left(5\right)\mathrm{}$ SUSY GUT and the $U\left(2\right)\mathrm{}$ model. The patterns and correlations of deviations from the standard model will be useful to discriminate the different SUSY models in future B experiments.

We study the lattice $N=1\mathrm{}$ Wess-Zumino model in two dimensions and we construct a sequence ${\rho }^{\mathrm{}\left(L\right)\mathrm{}}$ of exact lower bounds on its ground-state energy density $\rho ,$ converging to $\rho$ in the limit $\overrightarrow{L}\infty .$ The bounds ${\rho }^{\mathrm{}\left(L\right)\mathrm{}}$ can be computed numerically on a finite lattice with L sites and can be exploited to discuss dynamical symmetry breaking. The transition point is determined and compared with recent results based on large-scale Green function Monte Carlo simulations with good agreement.

We present the first study of the thermal effects on the quark-gluon mixed condensate $g〈\overline{q}{\sigma }_{\mu \nu }{G}_{\mu \nu }q〉,$ which is another chiral order parameter, in the $\mathrm{SU}{\mathrm{}\left(3\right)\mathrm{}}_c$ lattice QCD with the Kogut-Susskind fermion at the quenched level. Using the lattices at $\beta =6.0,$ 6.1, and 6.2 in high statistics, we calculate $g〈\overline{q}{\sigma }_{\mu \nu }{G}_{\mu \nu }q〉$ as well as $〈\overline{q}q〉$ in the chiral limit for $0\lesssim T\lesssim 500\mathrm{MeV}.$ Except for the sharp decrease of both the condensates around $T_c\simeq 280\mathrm{MeV},$ the thermal effects are found to be weak below $T_c.$ We also find that the ratio $m_0^2\equiv g〈\overline{q}{\sigma }_{\mu \nu }{G}_{\mu \nu }q〉/〈\overline{q}q〉$ is almost independent of the temperature even in the very vicinity of $T_c.$ This result indicates nontrivial similarity in the chiral behaviors of the two different condensates.

The cross sections for several $\gamma \overrightarrow{\gamma }\mathrm{VV}$ processes exhibit strong enhancements near threshold, where V denotes a vector meson. The pattern of these enhancements is not well understood; for example, $\gamma \overrightarrow{\gamma }{\rho }^0{\rho }^0$ shows an appreciable peak, while $\gamma \overrightarrow{\gamma }{\rho }^{+}{\rho }^{-}$ does not. Some possible mechanisms for this behavior are discussed. Tests are proposed involving production of systems containing heavier quarks, e.g., through the reaction $\gamma \overrightarrow{\gamma }J/\psi {\rho }^0.$ The importance of modeling ${\mathcal{l}}^{+}{\mathcal{l}}^{-}{\pi }^{+}{\pi }^{-}$ angular distributions in decays of threshold $J/\psi {\rho }^0$ enhancements is illustrated by comparing the expected distributions for S-wave decays of scalar particles and P-wave decays of pseudoscalar particles.

We derive the initial condition for the perturbative fragmentation function of a heavy quark through order $\mathcal{O}\left({\alpha }_s^2\right)$ in the $\overline{\mathrm{MS}}$ scheme. This initial condition is useful for computing heavy quark (or lepton, in case of QED) energy distributions from calculations with massless partons. In addition, the initial condition at $\mathcal{O}\left({\alpha }_s^2\right)$ can be used to resum collinear logarithms $\ln {(Q}^2{/m}^2)$ in heavy quark energy spectrum with next-to-next-to-leading logarithmic accuracy by solving the DGLAP equation.

A large number of treatments of the meson spectrum have been tried that consider mesons as quark-antiquark bound states. Recently, we used relativistic quantum “constraint” mechanics to introduce a fully covariant treatment defined by two coupled Dirac equations. For field-theoretic interactions, this procedure functions as a “quantum mechanical transform of the Bethe-Salpeter equation.” Here, we test its spectral fits against those provided by an assortment of models: Wisconsin model, Iowa State model, Brayshaw model, and the popular semirelativistic treatment of Godfrey and Isgur. We find that the fit provided by the two-body Dirac model for the entire meson spectrum competes with the best fits to partial spectra provided by the others and does so with the smallest number of interaction functions without additional cutoff parameters necessary to make other approaches numerically tractable. We discuss the distinguishing features of our model that may account for the relative overall success of its fits. Note especially that in our approach for QCD, the resulting pion mass and associated Goldstone behavior depend sensitively on the preservation of relativistic couplings that are crucial for its success when solved nonperturbatively for the analogous two-body bound states of QED.

We illustrate the exotic $\mathrm{SU}\left(3\right)\mathrm{}$ baryon submultiplets in the $\mathrm{SU}\left(4\right)\mathrm{}$ baryon multiplets predicted from the flavor $\mathrm{SU}\left(4\right)\mathrm{}$ collective-coordinate quantization, and investigate the exotic states with charm number $C$ $=\pm 1$ up to leading order of ${1/N}_c$ under chiral ${\mathrm{SU}\left(3\right)\mathrm{}}_L\times {\mathrm{SU}\left(3\right)\mathrm{}}_R$ symmetry and the heavy quark limit from bound state approach. We find that there exist the $\overline{15}$-plets and 24-plets with $C=1\mathrm{}$ and the $6¯$-plets, 15-plets and ${15}^{\prime }$-plets with $C=-1$ bounded in this approach, qualitatively consistent with predictions from the flavor $\mathrm{SU}\left(4\right)\mathrm{}$ collective-coordinate quantization. By fitting one unique parameter of leading $\mathrm{SU}\left(3\right)\mathrm{}$ flavor symmetry breaking term with the mass difference between ${\Xi }_c$ and ${\Sigma }_c$ and up to ${O(m}_Q^0{N}_c^{-1}),$ we give all the average masses of baryons in 6¯-plet and 15-plet. Several general relations of these masses without any parameter are also introduced.

We present an investigation of the pion’s electromagnetic form factor $F_{\pi }{(Q}^2)$ in the spacelike region utilizing two new ingredients: (i) a double-humped, end-point-suppressed pion distribution amplitude derived before via QCD sum rules with nonlocal condensates—found to comply at the $1\sigma$ level with the CLEO data on the $\pi \gamma$ transition—and (ii) analytic perturbation theory at the level of parton amplitudes for hadronic reactions. The computation of $F_{\pi }{(Q}^2)$ within this approach is performed at the next to leading order (NLO) of QCD perturbation theory (standard and analytic), including the evolution of the pion distribution amplitude at the same order. We consider the NLO corrections to the form factor in the $\overline{\mathrm{MS}}$ scheme with various renormalization scale settings and also in the ${\alpha }_V$ scheme. We find that using standard perturbation theory, the size of the NLO corrections is quite sensitive to the adopted renormalization scheme and scale setting. The main results of our analysis are the following: (i) Replacing the QCD coupling and its powers by their analytic images, both dependencies are diminished and the predictions for the pion form factor are quasi-scheme- and scale-setting independent. (ii) The magnitude of the factorized pion form factor, calculated with the aforementioned pion distribution amplitude, is only slightly larger than the result obtained with the asymptotic one in all considered schemes. (iii) Including the soft pion form factor via local duality and ensuring the Ward identity at $Q^2=0,$ we present predictions that are in remarkably good agreement with the existing experimental data both in trend and magnitude.