We study the Higgs boson pair production at the linear collider in the noncommutative extension of the standard model using the Seiberg-Witten map of this to the first order of the noncommutative parameter ${\Theta }_{\mu \nu }$. Unlike the standard model (where the process is forbidden) here the Higgs boson pair directly interacts with the photon. We find that the pair production cross section can be quite significant for the noncommutative scale $\Lambda$ lying in the range 0.5 TeV to 1.0 TeV. Using the experimental (LEP 2, Tevatron, and global electroweak fit) bound on the Higgs mass, we obtain $626\mathrm{GeV}\le \Lambda \le 974\mathrm{GeV}$.

We study the light $CP$-even neutral Higgs boson production in association with an electron and a jet at the possible CERN large hadron-electron collider within the minimal supersymmetric standard model. We investigate the possible supersymmetric effects on this process and compare our standard model numerical results with those in previous work. We present the leading-order and QCD next-to-leading-order corrected total cross sections and the distributions of the transverse momenta of the final electron, the light neutral Higgs boson, and jet in the minimal supersymmetric standard model. Our results show that the scale dependence of the leading-order cross section is obviously reduced by the QCD next-to-leading-order corrections. The $K$ factor of the QCD correction to the total cross section at the large hadron-electron collider varies from 0.0893 to 1.048 when the factorization/renormalization scale $\mu$ goes up from $0.2m_Z$ to $3.8m_Z$ in our chosen parameter space.

We consider the compatibility of DAMA/LIBRA, CoGeNT, XENON10 and XENON100 results for spin-independent (SI) dark matter weakly interacting massive particles, particularly at low masses ($\sim 10\mathrm{GeV}$), assuming a standard dark matter halo. The XENON bounds depend on the scintillation efficiency factor ${\mathcal{L}}_{\mathrm{eff}}$ for which there is considerable uncertainty. Thus we consider various extrapolations for ${\mathcal{L}}_{\mathrm{eff}}$ at low energy. With the ${\mathcal{L}}_{\mathrm{eff}}$ measurements we consider, XENON100 results are found to be insensitive to the low-energy extrapolation. We find the strongest bounds are from XENON10, rather than XENON100, due to the lower energy threshold. For reasonable choices of ${\mathcal{L}}_{\mathrm{eff}}$ and for the case of SI elastic scattering, XENON10 is incompatible with the DAMA/LIBRA $3\sigma$ region and severely constrains the 7–12 GeV WIMP mass region of interest published by the CoGeNT Collaboration.

We study a modified version of a $U(1{)}_{B-L}$ gauged MSSM that was recently shown to produce a new source of leptogenesis through the $CP$ asymmetry of sneutrinos and antisneutrinos [K. S. Babu, Yanzhi Meng, and Zurab Tavartkiladze, Phys. Lett. B 681, 37 (2009)]. By taking all superpotential terms and couplings between the MSSM Higgs and $B-L$ scalar sectors into account we find that the model allows a large enough $CP$ violation to explain the observed baryon number to entropy ratio. Monte Carlo analysis shows that a large amount of $CP$ violation can be produced in the decays of the $B-L$ Higgs bosons and that there are two dominating channels that drive $CP$ violation.

We study the phase structure of mixed-action QCD with two Wilson sea quarks and any number of chiral valence quarks (and ghosts), starting from the chiral Lagrangian. A priori the effective theory allows for a rich phase structure, including a phase with a condensate made of sea and valence quarks. In such a phase, mass eigenstates would become admixtures of sea and valence fields, and pure-sea correlation functions would depend on the parameters of the valence sector, in contradiction with the actual setup of mixed-action simulations. Using that the spectrum of the chiral Dirac operator has a gap for nonzero quark mass we prove that spontaneous symmetry breaking of the flavor symmetries can only occur within the sea sector. This rules out a mixed condensate and implies restrictions on the low-energy constants of the effective theory.

Using (9.32, 5.88) million ${\rm Y}(2S,3S)$ decays taken with the CLEO III detector, we obtain five product branching fractions for the exclusive processes ${\rm Y}(2S)\to \gamma {\chi }_{b0,1,2}(1P)\to \gamma \gamma {\rm Y}(1S)$ and ${\rm Y}(3S)\to \gamma {\chi }_{b1,2}(1P)\to \gamma \gamma {\rm Y}(1S)$. We observe the transition ${\chi }_{b0}(1P)\to \gamma {\rm Y}(1S)$ for the first time. Using the known branching fractions for $\mathcal{B}[{\rm Y}(2S)\to \gamma {\chi }_{bJ}(1P)]$, we extract values for $\mathcal{B}[{\chi }_{bJ}(1P)\to \gamma {\rm Y}(1S)]$ for $J=0$, 1, 2. In turn, these values can be used to unfold the ${\rm Y}(3S)$ product branching fractions to obtain values for $\mathcal{B}[{\rm Y}(3S)\to \gamma {\chi }_{b1,2}(1P)]$ for the first time individually. Comparison of these with each other and with the branching fraction $\mathcal{B}[{\rm Y}(3S)\to \gamma {\chi }_{b0}]$ previously measured by CLEO provides tests of relativistic corrections to electric dipole matrix elements.

We perform a Dalitz plot analysis of about 100 000 $D_s^{+}$ decays to $K^{+}{K}^{-}{\pi }^{+}$ and measure the complex amplitudes of the intermediate resonances which contribute to this decay mode. We also measure the relative branching fractions of $D_s^{+}\to K^{+}{K}^{+}{\pi }^{-}$ and $D_s^{+}\to K^{+}{K}^{+}{K}^{-}$. For this analysis we use a 384 ${\mathrm{fb}}^{-1}$ data sample, recorded by the BABAR detector at the PEP-II asymmetric-energy $e^{+}{e}^{-}$ collider running at center-of-mass energies near 10.58 $\mathrm{GeV}$.

We investigate energy dissipation associated with the motion of the scalar condensate in a holographic superconductor model constructed from the charged scalar field coupled to the Maxwell field. Upon application of constant magnetic and electric fields, we analytically construct the vortex-flow solution and find the vortex-flow resistance near the second-order phase transition where the scalar condensate begins. The characteristic feature of the nonequilibrium state agrees with the one predicted by the time-dependent Ginzburg-Landau (TDGL) theory. We evaluate the kinetic coefficient in the TDGL equation along the line of the second-order phase transition. At zero magnetic field, the other coefficients in the TDGL equation are also evaluated just below the critical temperature.

We use anti–de Sitter/CFT duality to compute in $\mathcal{N}=4$ Yang-Mills theory the finite temperature spatial correlator $G(r)$ of the scalar operator $F^2$, integrated over imaginary time. The computation is carried out both at zero frequency and integrating the spectral function over frequencies. The result is compared with a perturbative computation in finite $T$ $\mathrm{SU}(N_c)$ Yang-Mills theory.

We present a systematic approach to the linearized Yang-Mills-Higgs equations in the background of a ’t Hooft-Polyakov monopole and use it to unify and extend previous studies of their spectral properties. We show that a quaternionic formulation allows for a compact and efficient treatment of the linearized equations in the Bogomol’nyi-Prasad-Sommerfield limit of vanishing Higgs self-coupling and use it to study both scattering and bound states. We focus on the sector of vanishing generalized angular momentum and analyze it numerically, putting zero-energy bound states, Coulomb bound states, and infinitely many Feshbach resonances into a coherent picture. We also consider the linearized Yang-Mills-Higgs equations with nonvanishing Higgs self-coupling and confirm the occurrence of Feshbach resonances in this situation.

We study a unification model for dark energy, dark matter, and inflation with a single scalar field with noncanonical kinetic term. In this model, the kinetic term of the Lagrangian accounts for the dark matter and dark energy, and at early epochs, a quadratic potential accounts for slow roll inflation. The present work is an extension to the work by Bose and Majumdar [Phys. Rev. D 79, 103517 (2009).] with a more general kinetic term that was proposed by Chimento in Phys. Rev. D 69, 123517 (2004). We demonstrate that the model is viable at the background and linear perturbation levels.

Integrated Sachs-Wolfe (ISW) effect can be estimated by cross-correlating the cosmic microwave background (CMB) sky with tracers of the local matter distribution. At late cosmic time, the dark energy–induced decay of gravitation potential generates a cross correlation signal on large angular scales. The dominant noise is the intrinsic CMB anisotropies from the inflationary epoch. In this paper we use CMB polarization to reduce this intrinsic noise. We cross-correlate the microwave sky observed by Wilkinson Microwave Anisotropy Probe (WMAP) with the radio source catalog compiled by NRAO VLA Sky Survey (NVSS) to study the efficiency of the noise suppression. We find that the error bars are reduced by about 4 to 14% and the statistical power in the signal is improved.

We calculate the complete next-to-leading order (NLO) QCD corrections (including SUSY QCD corrections) to the inclusive total cross sections of the associated production processes $pp\to A^0\gamma +X$ in the minimal supersymmetric standard model (MSSM) at the CERN Large Hadron Collider (LHC). Our results show that the enhancement of the total cross sections from the NLO QCD corrections can reach $25\%\sim 15\%$ for $200\mathrm{GeV}<m_A<500\mathrm{GeV}$ and $\tan \beta =50$. The scale dependence of the total cross section is improved by the NLO corrections in general. We also show the Monte Carlo simulation results for the ${\tau }^{+}{\tau }^{-}+\gamma$ signature including the complete NLO QCD effects, and find an observable signature above the standard model (SM) background for a normal luminosity of $100{\mathrm{fb}}^{-1}$ at the LHC.

We study the cosmological evolution of a single BPS D-brane coupled to gravity in the absence of potential. When such a D-brane moves in the bulk with nonvanishing velocity, it tends to slow down to zero velocity via mechanisms like gravitational wave leakage to the bulk, losing its kinetic energy to fuel the expansion of the Universe on the D-brane. If the initial velocity of the D-brane is high enough, the Universe on the D-brane undergoes a dustlike stage at early times and an acceleration stage at late times, realizing the original Chaplygin gas model. When the D-brane velocity is initially zero, the D-brane will always remain fixed at some position in the bulk, with the brane tension over the Plank mass squared as a cosmological constant. It is further shown that this kind of fixed brane universe can arise as defects from tachyon inflation on a non-Bogomol’nyi-Prasad-Sommerfeld D-brane with one dimension higher.

It is shown that, in the two brane time variation model framework, if the hidden brane tension varies according to the phenomenological Eötvös law, the visible brane tension behavior is such that its time derivative is negative in the past and positive after a specific time of cosmological evolution. This behavior is interpreted in terms of a useful mechanical system analog and its relation with the variation of the Newtonian (effective) gravitational “constant” is explored.

The attractor mechanism in five dimensional Einstein-Maxwell Chern-Simons theory is studied. The expression of the five-dimensional rotating black object potential depending on Taub-Newman-Unti-Tamburino, electric and magnetic charges as well as on all the scalar and gauge fields, is investigated. The first order formalism in $d=5$ is constructed and analyzed. We derive a general expression defining the fake superpotential which is valid for all charge configurations. An explicit expression for the fake superpotential is constructed, for all very special geometries, in the case of vanishing Taub-Newman-Unti-Tamburino charge. We carry out an analogous construction in the very special geometries corresponding to $t^3$ and $stu$ models, for the most general charge configurations. The attractor flows and horizon values of all fields are given.

We study the entanglement entropy $S_C$ of the massless free scalar field on the outside region $C$ of two black holes $A$ and $B$ whose radii are $R_1$ and $R_2$ and how it depends on the distance $r(\gg R_1,R_2)$ between two black holes. If we can consider the entanglement entropy as thermodynamic entropy, we can see the entropic force acting on the two black holes from the $r$ dependence of $S_C$. We develop the computational method based on that of Bombelli et al. to obtain the $r$ dependence of $S_C$ of scalar fields whose Lagrangian is quadratic with respect to the scalar fields. First, we study $S_C$ in ($d+1$)-dimensional Minkowski spacetime. In this case the state of the massless free scalar field is the Minkowski vacuum state, and we replace two black holes by two imaginary spheres and take the trace over the degrees of freedom residing in the imaginary spheres. We obtain the leading term of $S_C$ with respect to $1/r$. The result is $S_C=S_A+S_B+\frac{1}{r^{2d-2}}G(R_1,R_2)$, where $S_A$ and $S_B$ are the entanglement entropy on the inside region of $A$ and $B$, respectively, and $G(R_1,R_2)\le 0$. We do not calculate $G(R_1,R_2)$ in detail, but we show how to calculate it. In the black hole case we use the method used in the Minkowski spacetime case with some modifications. We show that $S_C$ can be expected to be the same form as that in the Minkowski spacetime case. But in the black hole case, $S_A$ and $S_B$ depend on $r$, so we do not fully obtain the $r$ dependence of $S_C$. Finally, we assume that the entanglement entropy can be regarded as thermodynamic entropy and consider the entropic force acting on two black holes. We argue how to separate the entanglement entropic force from other forces and how to cancel $S_A$ and $S_B$ whose $r$ dependences are not obtained. Then we obtain the physical prediction, which can be tested experimentally in principle.

A calculation of the bulk viscosity for the massive Gross-Neveu model at zero fermion chemical potential is presented in the large-$N$ limit. This model resembles QCD in many important aspects: it is asymptotically free, has a dynamically generated mass gap, and for zero bare fermion mass it is scale invariant at the classical level (broken through the trace anomaly at the quantum level). For our purposes, the introduction of a bare fermion mass is necessary to break the integrability of the model, and thus to be able to study momentum transport. The main motivation is, by decreasing the bare mass, to analyze whether there is a correlation between the maximum in the trace anomaly and a possible maximum in the bulk viscosity, as recently conjectured. After numerical analysis, I find that there is no direct correlation between these two quantities: the bulk viscosity of the model is a monotonically decreasing function of the temperature. I also comment on the sum rule for the spectral density in the bulk channel, as well as on implications of this analysis for other systems.

We generalize the factorized resummation of multipolar waveforms introduced by Damour, Iyer, and Nagar to spinning black holes. For a nonspinning test particle spiraling a Kerr black hole in the equatorial plane, we find that factorized multipolar amplitudes which replace the residual relativistic amplitude $f_{\ell m}$ with its $\ell$th root, ${\rho }_{\ell m}=f_{\ell m}^{1/\ell }$, agree quite well with the numerical amplitudes up to the Kerr-spin value $q\le 0.95$ for orbital velocities $v\le 0.4$. The numerical amplitudes are computed solving the Teukolsky equation with a spectral code. The agreement for prograde orbits and large spin values of the Kerr black-hole can be further improved at high velocities by properly factoring out the lower-order post-Newtonian contributions in ${\rho }_{\ell m}$. The resummation procedure results in a better and systematic agreement between numerical and analytical amplitudes (and energy fluxes) than standard Taylor-expanded post-Newtonian approximants. This is particularly true for higher-order modes, such as (2,1), (3,3), (3,2), and (4,4), for which less spin post-Newtonian terms are known. We also extend the factorized resummation of multipolar amplitudes to generic mass-ratio, nonprecessing, spinning black holes. Lastly, in our study we employ new, recently computed, higher-order post-Newtonian terms in several subdominant modes and compute explicit expressions for the half and one-and-half post-Newtonian contributions to the odd-parity (current) and even-parity (odd) multipoles, respectively. Those results can be used to build more accurate templates for ground-based and space-based gravitational-wave detectors.

We simulate head-on collisions from rest at large separation of binary white dwarf-neutron stars (WDNSs) in full general relativity. Our study serves as a prelude to our analysis of the circular binary WDNS problem. We focus on compact binaries whose total mass exceeds the maximum mass that a cold-degenerate star can support, and our goal is to determine the fate of such systems. A fully general relativistic hydrodynamic computation of a realistic WDNS head-on collision is prohibitive due to the large range of dynamical time scales and length scales involved. For this reason, we construct an equation of state (EOS) which captures the main physical features of neutron stars (NSs) while, at the same time, scales down the size of white dwarfs (WDs). We call these scaled-down WD models “pseudo-WDs (pWDs).” Using pWDs, we can study these systems via a sequence of simulations where the size of the pWD gradually increases toward the realistic case. We perform two sets of simulations; One set studies the effects of the NS mass on the final outcome, when the pWD is kept fixed. The other set studies the effect of the pWD compaction on the final outcome, when the pWD mass and the NS are kept fixed. All simulations show that after the collision, 14%–18% of the initial total rest mass escapes to infinity. All remnant masses still exceed the maximum rest mass that our cold EOS can support ($1.92M_{\odot }$), but no case leads to prompt collapse to a black hole. This outcome arises because the final configurations are hot. All cases settle into spherical, quasiequilibrium configurations consisting of a cold NS core surrounded by a hot mantle, resembling Thorne-Zytkow objects. Extrapolating our results to realistic WD compactions, we predict that the likely outcome of a head-on collision of a realistic, massive WDNS system will be the formation of a quasiequilibrium Thorne-Zytkow-like object.