New physics (NP) in charmless strangeness-changing $B$ and $B_s$ decays, which are dominated by the $b\to s$ penguin amplitudes, can either preserve isospin or change it by one unit. A general formalism is presented studying pairs of processes related to each other by isospin reflection. We discuss information on $\Delta I$ in NP amplitudes, provided by time-integrated $CP$-violating rate asymmetries in $B^{+}$ and $B^0$ decays (or in $B_s$ decays), differences between rates for isospin-reflected processes, and coefficients $S$ of $\sin \Delta mt$ in time-dependent $CP$ asymmetries. These four asymmetries in $B^{+}$ and $B^0$ decays (or five asymmetries in $B_s$ decays) are shown to determine the magnitude and $CP$-violating phase of a potential isovector NP amplitude, and the imaginary part of an isoscalar amplitude, assuming that strong phases in NP amplitudes are negligible. This information may be compared with predictions of specific models, for which we discuss a few examples.

We develop the linear equations that describe graviton perturbations of ${\mathrm{AdS}}_5$-Schwarzschild generated by a string trailing behind an external quark moving with constant velocity. Solving these equations allows us to evaluate the stress tensor in the boundary gauge theory. Components of the stress tensor exhibit directional structures in Fourier space at both large and small momenta. We comment on the possible relevance of our results to relativistic heavy-ion collisions.

We calculate the emission spectrum for vacuum Cerenkov radiation in Lorentz-violating extensions of electrodynamics. We develop an approach that works equally well in the presence or the absence of birefringence. In addition to confirming earlier work, we present the first calculation relevant to Cerenkov radiation in the presence of a birefringent photon $k_F$ term, calculating the lower-energy part of the spectrum for that case.

We investigate the correlation between the neutrino mass limit and dark energy with the time evolving equation of state. Parametrizing dark energy as $w=w_0+w_1*z/(1+z)$, we make a global fit using Markov Chain Monte Carlo technique to determine $w_0$, $w_1$, neutrino mass as well as other cosmological parameters simultaneously. We pay particular attention to the correlation between neutrino mass $\Sigma m_{\nu }$ and $w_1$ using current cosmological observations as well as the future simulated data sets such as PLANCK, SNAP, and LAMOST.

We study flavor changing effects on the $pp\to bc{H}^{\pm }+X$ process at the Large Hadron Collider, which are inspired by the left-handed up-type squark mixings in the minimal supersymmetric standard model (MSSM). We find that the SUSY QCD radiative corrections to $bc{H}^{\pm }$ coupling can significantly enhance the cross sections at the tree level by a factor about $1.5\sim 5$ with our choice of parameters. We conclude that the squark-mixing mechanism in the MSSM makes the $pp\to bc{H}^{\pm }+X$ process a new channel for discovering a charged Higgs boson and investigating flavor changing effects.

It is the first time that the study of three-body baryonic $B$ decays offers an independent determination of the nucleon form factors for the timelike four momentum transfer ($t>0$) region, such as $G_M^{p,n}(t)$ of vector currents and those of axial ones. Explicitly, from the data of ${\overline{B}}^0\to n\overline{p}{D}^{*+}$ and $\Lambda \overline{p}{\pi }^{+}$ we find a constant ratio of $G_M^n(t)/G_M^p(t)=-1.3\pm 0.4$, which supports the FENICE experimental result. The vector and axial-vector form factors of $p\overline{n}$, $p\overline{p}$ and $n\overline{n}$ pairs due to weak currents are also presented, which can be tested in future experiments.

A study of charged current induced antineutrino interactions from nuclei has been done for the intermediate energy antineutrinos and applied to ${}^{12}\mathrm{C}$, relevant for ongoing experiment by MiniBooNE collaboration. The calculations have been done for the quasielastic and inelastic lepton production as well as for the incoherent and the coherent pion production processes. The calculations are done in local density approximation. In the case of the quasielastic reaction the effects of Pauli blocking, Fermi motion effects, renormalization of weak transition strengths in nuclear medium and the Coulomb distortion of the outgoing lepton have been taken into account. For the inelastic processes the calculations have been done in the $\Delta$ dominance model and take into account the effect of Pauli blocking, Fermi motion of the nucleon, and renormalization of $\Delta$ properties in a nuclear medium. The effect of final state interactions of pions is also taken into account. The numerical results for the total cross sections for the charged current quasielastic scattering and incoherent pion production processes are compared with earlier experimental results available in freon and freon-propane. It is found that nuclear medium effects give strong reduction in the cross sections leading to satisfactory agreement with the available data.

We reconstruct ${\overline{B}}^0\to D_s^{-}{D}^{+}$ decays using a sample of $449\times {10}^6$ $B\overline{B}$ pairs recorded by the Belle experiment, and measure the branching fraction to be $\mathcal{B}({\overline{B}}^0\to D_s^{-}{D}^{+})=[7.5\pm 0.2(\mathrm{stat})\pm 0.8(\mathrm{syst})\pm 0.8({\mathcal{B}}^{\prime }s)]\times {10}^{-3}$. A search for the related decay ${\overline{B}}^0\to D_s^{+}{D}_s^{-}$ is also performed. Since we observe no statistically significant signal, an upper limit on the branching fraction is set at $3.6\times {10}^{-5}$ (90% C.L.).

We report on progress in determining the complete form of vertex operators for the IIB matrix model. The exact expressions are obtained for those emitting massless IIB supergravity fields up to sixth order in the light-cone superfield, in which the conjugate gravitino and conjugate two-form vertex operators are newly determined. We also provide a consistency check by computing the kinematical factor of a four-point graviton amplitude in a $D$-instanton background. We conjecture that the low-energy effective action of the IIB matrix model at large $N$ is given by tree-level supergravity coupled to the vertex operators.

The explicit one-loop renormalizability of pure Yang-Mills theory with Lorentz violation is demonstrated. The result is consistent with multiplicative renormalization as the required counterterms are consistent with a single rescaling of the Lorentz-violation parameters. In addition, the resulting beta functions indicate that the $CPT$-even Lorentz-violating terms increase with energy scale in opposition to the asymptotically free gauge coupling and $CPT$-odd terms. The calculations are performed at lowest order in the Lorentz-violating terms as they are assumed small.

We study the emission of gravitons by a homogeneous brane with the Gauss-Bonnet term into an anti–de Sitter five dimensional bulk spacetime. It is found that the graviton emission depends on the curvature scale and the Gauss-Bonnnet coupling and that the amount of emission generally decreases. Therefore nucleosynthesis constraints are easier to satisfy by including the Gauss-Bonnet term.

We discuss an instability in a large class of models where dark energy is coupled to matter. In these models the mass of the scalar field is much larger than the expansion rate of the Universe. We find models in which this instability is absent, and show that these models generically predict an apparent equation of state for dark energy smaller than $-1$, i.e., superacceleration. These models have no acausal behavior or ghosts.

While the accelerated expansion of the Universe is by now well established, an underlying scalar-field potential possibly responsible for this acceleration remains unconstrained. We present an attempt to reconstruct this potential using recent SN data, under the assumption that the acceleration is driven by a single scalar field. Current approaches to such reconstructions are based upon simple parametric descriptions of either the luminosity distance or the dark energy equation of state. We find that these various approximations lead to a range of derived evolutionary histories of the dark energy equation of state (although there is considerable overlap between the different potential shapes allowed by the data). Instead of these indirect reconstruction schemes, we discuss a technique to determine the potential directly from the data by expressing it in terms of a binned scalar field. We apply this technique to a recent SN data set, and compare the results with model-dependent approaches. In a similar fashion to direct estimates of the dark energy equation of state, we advocate direct reconstruction of the scalar-field potential as a way to minimize prior assumptions on the shape, and thus minimize the introduction of bias in the derived potential.

Analytical radiative corrections of order $(\alpha /\pi )(q/M_1)$ are calculated for the four-body region of the Dalitz plot of baryon semileptonic decays when the ${\widehat{\mathbf{s}}}_1·\widehat{\mathit{l}}$ correlation is present. Once the final result is available, it is possible to exhibit it in terms of the corresponding final result of the three-body region following a set of simple changes in the latter, except for a few exceptions. We cover two cases, a charged and a neutral polarized decaying baryon.

The implications of the LEP Higgs bounds on the MSSM stop masses and mixing are compared in two different regions of the Higgs parameter space. The first region is the Higgs decoupling limit, in which the bound on the mass of the lighter Higgs is $m_h\ge 114.4\mathrm{GeV}$, and the second region is near a nondecoupling limit with $m_h\simeq 93\mathrm{GeV}$, in which the masses of all the physical Higgs bosons are required to be light. Additional constraints from the electroweak $S$- and $T$-parameter and the decays $B\to X_s\gamma$ and $B_s\to {\mu }^{+}{\mu }^{-}$, which also constrain the Higgs and/or stop sector, are considered. In some regions of the MSSM parameter space these additional constraints are stronger than the LEP Higgs bounds. Implications for the tuning of electroweak symmetry breaking are also discussed.

Using the exisiting experimental data for hyperon semileptonic decays and the flavor-singlet axial-vector charge $g_A^{(0)}$ from polarized deep inelastic scattering of the proton, we derive the decay width of the ${\Theta }^{+}$ pentaquark baryon. We take into account the effects of flavor SU(3) symmetry breaking within the framework of the chiral quark-soliton model. All dynamical parameters of the model are fixed by using the five experimental hyperon semileptonic decay constants and flavor-singlet axial-vector charge. We obtain the numerical results of the decay width of the ${\Theta }^{+}$ pentaquark baryon as a function of the pion-nucleon sigma term ${\Sigma }_{\pi N}$ and investigate the dependence of the decay width of the ${\Theta }^{+}$ on the $g_A^{(0)}$, varying the $g_A^{(0)}$ within the range of the experimental uncertainty. We demonstrate that the combined values of all known semileptonic decays with the generally accepted value of $g_A^{(0)}\approx 0.3$ for the proton are compatible with a small decay width ${\Gamma }_{\Theta KN}$ of the ${\Theta }^{+}$ pentaquark, i.e. ${\Gamma }_{\Theta KN}\le 1\mathrm{MeV}$.

Neutrinos escaping from a core collapse supernova a few seconds after bounce pass through the shock wave, where they may encounter one or more resonances corresponding to $\Delta m_{\mathrm{atm}}^2$. The neutrino mass eigenstates in matter may stay coherent between these multiple resonances, giving rise to oscillations in the survival probabilities of neutrino species. We provide an analytical approximation to these inevitable phase effects, that relates the density profile of the shock wave to the oscillation pattern. The phase effects are present only if the multiple resonances encountered by neutrinos are semiadiabatic, which typically happens for ${10}^{-5}\lesssim {sin}^2{\theta }_{13}\lesssim {10}^{-3}$. The observability of these oscillations is severely limited by the inability of the detectors to reconstruct the neutrino energy faithfully. For typical shock wave profiles, the detection of these phase effects seems rather unlikely. However, if the effects are indeed identified in the ${\overline{\nu }}_e$ spectra, they would establish inverted hierarchy and a nonzero value of ${\theta }_{13}$.

To gain insight into how bulk locality emerges from the holographic conformal field theory (CFT), we reformulate the bulk-to-boundary map in as local a way as possible. In previous work, we carried out this program for Lorentzian anti-de Sitter (AdS), and showed the support on the boundary could always be reduced to a compact region spacelike separated from the bulk point. In the present work the idea is extended to a complexified boundary, where spatial coordinates are continued to imaginary values. This continuation enables us to represent a local bulk operator as a CFT operator with support on a finite disc on the complexified boundary. We treat general AdS in Poincaré coordinates and ${\mathrm{AdS}}_3$ in Rindler coordinates. We represent bulk operators inside the horizon of a Banados-Teitelboim-Zanelli (BTZ) black hole and we verify that the correct bulk two-point functions are reproduced, including the divergence when one point hits the BTZ singularity. We comment on the holographic description of black holes formed by collapse and discuss locality and holographic entropy counting at finite $N$.

Wave extraction plays a fundamental role in the binary black hole simulations currently performed in numerical relativity. Having a well-defined procedure for wave extraction, which matches simplicity with efficiency, is critical especially when comparing waveforms from different simulations. Recently, progress has been made in defining a general technique which uses Weyl scalars to extract the gravitational wave signal, through the introduction of the quasi-Kinnersley tetrad. This procedure has been used successfully in current numerical simulations; however, it involves complicated calculations. The work in this paper simplifies the procedure by showing that the choice of the quasi-Kinnersley tetrad is reduced to the choice of the timelike vector used to create it. The spacelike vectors needed to complete the tetrad are then easily identified, and it is possible to write the expression for the Weyl scalars in the right tetrad, as simple functions of the electric and magnetic parts of the Weyl tensor.

We derive the low-energy effective theory of gravity for a generalized Randall-Sundrum scenario, allowing for a third self-gravitating brane to live in the 5D bulk spacetime. At zero order the 5D spacetime is composed of two slices of anti-de Sitter spacetime, each with a different curvature scale, and the 5D Weyl tensor vanishes. Two boundary branes are at the fixed points of the orbifold whereas the third brane is free to move in the bulk. At first order, the third brane breaks the otherwise continuous evolution of the projection of the Weyl tensor normal to the branes. We derive a junction condition for the projected Weyl tensor across the bulk brane, and combining this constraint with the junction condition for the extrinsic curvature tensor, allows us to derive the first-order field equations on the middle brane. The effective theory is a generalized Brans-Dicke theory with two scalar fields. This is conformally equivalent to Einstein gravity and two scalar fields, minimally coupled to the geometry, but nonminimally coupled to matter on the three branes.