If the energy density of the Universe before nucleosynthesis is dominated by a scalar field $\varphi$ that decays and reheats the plasma to a temperature $T_{\mathrm{RH}}$ smaller than the standard neutralino freeze-out temperature, the neutralino relic density differs from its standard value. In this case, the relic density depends on two additional parameters: $T_{\mathrm{RH}}$, and the number of neutralinos produced per $\varphi$ decay per unit mass of the $\varphi$ field. In this paper, we numerically study the neutralino relic density as a function of these reheating parameters within minimal supersymmetric standard models and show that the dark matter constraint can almost always be satisfied.

From the nature of the muon production processes, it can be seen that the ratio of positive to negative cosmic muons has important information in both “the atmospheric neutrino problem,” and “the hadronic interactions.” We have carried out an experiment for the measurement of the muon charge ratio in the cosmic ray flux in momentum range $0.112–0.178\mathrm{GeV}/\mathrm{c}$. The muon charge ratio is found to be $1.21\pm 0.01$ with a mean zenith angle of $32°\pm 5°$. From the measurements it has been obtained a zenithal angle distribution of muons as $I(\theta )=I(0){cos}^n\theta$ with $n=1.95\pm 0.13$. An asymmetry has been observed in East-West directions because of the geomagnetic field. Meanwhile, in about the same momentum range, positive and negative muons have been studied on the basis of Monte Carlo simulations of the extensive air shower developement (Cosmic Ray Simulations for Kascade), using the Quark Gluon String model with JETs model as generator.

Treating the MSSM as an effective theory below a threshold scale $\Lambda$, we study the consequences of having dimension-five operators in the superpotential for flavor and $CP$-violating processes. Below the supersymmetric threshold such terms generate flavor changing and/or $CP$-odd effective operators of dimension six composed from the standard model fermions, that have the interesting property of decoupling linearly with the threshold scale, i.e. as $1/(\Lambda m_{\mathrm{soft}})$, where $m_{\mathrm{soft}}$ is the scale of soft supersymmetry breaking. The assumption of weak-scale supersymmetry, together with the stringent limits on electric dipole moments and lepton flavor-violating processes, then provides sensitivity to $\Lambda$ as high as ${10}^7-{10}^9\mathrm{GeV}$. We discuss the varying sensitivity to these scales within several MSSM benchmark scenarios and also outline the classes of UV physics which could generate these operators.

The charged current one pion production induced by ${\nu }_{\mu }$ from nucleons and nuclei like ${}^{12}\mathrm{C}$ and ${}^{16}\mathrm{O}$ nuclei has been studied. The calculations have been done for the incoherent and the coherent processes from nuclear targets assuming the $\Delta$ dominance model and taking 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 has been taken into account. The theoretical uncertainty in the total cross sections due to various parametrizations of the weak transition form factors used in literature has been studied. The numerical results for the total cross sections are compared with the recent preliminary results from the MiniBooNE collaboration on ${}^{12}\mathrm{C}$ and could be useful in analyzing future data from the K2K collaboration.

We evaluate the model-dependent piece of $O(\alpha )$ long-distance radiative corrections to ${\tau }^{-}\to {\pi }^{-}{\pi }^0{\nu }_{\tau }$ decays by using a meson dominance model. We find that these corrections to the di-pion invariant mass spectrum are smaller than in previous calculations based on chiral perturbation theory. The corresponding correction to the photon inclusive rate is tiny ($-0.15\%$) but it can be of relevance when new measurements reach better precision.

We consider bulk fields coupled to the graviton in a Lorentz violating fashion. We expect that the overly tested Lorentz symmetry might set constraints on the induced Lorentz violation in the brane, and hence on the dynamics of the interaction of bulk fields on the brane. We also use the requirement for Lorentz symmetry to constrain the cosmological constant observed on the brane.

We derive an expression for the second-order gravitational self-force that acts on a self-gravitating compact object moving in a curved background spacetime. First we develop a new method of derivation and apply it to the derivation of the first-order gravitational self-force. Here we find that our result conforms with the previously derived expression. Next we generalize our method and derive a new expression for the second-order gravitational self-force. This study also has a practical motivation: The data analysis for the planned gravitational wave detector LISA requires construction of waveform templates for the expected gravitational waves. Calculation of the two leading orders of the gravitational self-force will enable one to construct highly accurate waveform templates, which are needed for the data analysis of gravitational waves that are emitted from extreme mass-ratio binaries.

We calculate magnetic moments of light baryons and $N\to \Delta \gamma$ transition characteristics using a manifestly Lorentz covariant chiral quark approach for the study of baryons as bound states of constituent quarks dressed by a cloud of pseudoscalar mesons.

We present a measurement of the $t\overline{t}$ production cross section using events with one charged lepton and jets from $p\overline{p}$ collisions at a center-of-mass energy of 1.96 TeV. A $b$-tagging algorithm based on the probability of displaced tracks coming from the event interaction vertex is applied to identify $b$ quarks from top decay. Using $318{\mathrm{pb}}^{-1}$ of data collected with the CDF II detector, we measure the $t\overline{t}$ production cross section in events with at least one restrictive (tight) $b$-tagged jet and obtain ${8.9}_{-1.0}^{+1.0}(\mathrm{stat}{)}_{-1.0}^{+1.1}(\mathrm{syst})\mathrm{pb}$. The cross section value assumes a top quark mass of $m_t=178\mathrm{GeV}/c^2$ in the acceptance corrections. The dependence of the cross section on $m_t$ is presented in the paper. This result is consistent with other CDF measurements of the $t\overline{t}$ cross section using different samples and analysis techniques, and has similar systematic uncertainties. We have also performed consistency checks by using the $b$-tagging probability function to vary the signal-to-background ratio and also using events that have at least two $b$-tagged jets.

We explore tensor mesons in AdS/QCD focusing on $f_2(1270)$, the lightest spin-2 resonance in QCD. We find that the $f_2$ mass and the partial width $\Gamma (f_2\to \gamma \gamma )$ are in very good agreement with data. In fact, the dimensionless ratio of these two quantities comes out to be within the current experimental bound. The result for this ratio depends only on $N_c$ and $N_f$, and the quark and glueball content of the operator responsible for the $f_2$; more importantly, it does not depend on chiral symmetry breaking and so it is both independent of much of the arbitrariness of AdS/QCD and completely out of reach of chiral perturbation theory. For comparison, we also explore $f_2\to \pi \pi$, which, because of its sensitivity to the UV corrections, has much more uncertainty. We also calculate the masses of the higher spin resonances on the Regge trajectory of the $f_2$, and find they compare favorably with experiment.

In this paper we provide some circumstantial evidence for a holographic duality between bubble nucleation in an eternally inflating universe and a Euclidean conformal field theory (CFT). The holographic correspondence (which is different than Strominger’s de Sitter (dS)/CFT duality) relates the decay of ($3+1$)-dimensional de Sitter space to a two-dimensional CFT. It is not associated with pure de Sitter space, but rather with Coleman-De Luccia bubble nucleation. Alternatively, it can be thought of as a holographic description of the open, infinite, Friedmann-Robertson-Walker (FRW) cosmology that results from such a bubble. The conjectured holographic representation is of a new type that combines holography with the Wheeler-DeWitt formalism to produce a Wheeler-DeWitt theory that lives on the spatial boundary of a $k=-1$ FRW cosmology. We also argue for a more ambitious interpretation of the Wheeler-DeWitt CFT as a holographic dual of the entire Landscape.

We show that the vacuum structure of a generic multi-Higgs-doublet model shares several important features with the vacuum structure of the two and three Higgs-doublet model. In particular, one can still define the usual charge breaking, spontaneous $CP$ breaking, and normal (charge and $CP$ preserving) stationary points. We analyze the possibility of charge or spontaneous $CP$ breaking by studying the relative depth of the potential in each of the possible stationary points.

The dynamics of a self-gravitating matter shell in general relativity is discussed in general. The case of a spherical shell composed of an arbitrary ideal fluid is then considered, and its Lagrangian function is derived from first principles. For this purpose, the standard Hilbert action is modified by an appropriate surface term at spatial infinity. The total Hamiltonian of the composed “$\mathrm{\text{shell}}+\mathrm{\text{gravity}}$” system is then calculated. Known results for the dust matter are recovered as particular cases. The above “surface renormalization” of the Hilbert action may be used for any spatially flat spacetime.

We put forward a new model-independent reconstruction scheme for dark energy which utilizes the expected geometrical features of the luminosity-distance relation. The important advantage of this scheme is that it does not assume explicit ansatzes for cosmological parameters but only some very general cosmological properties via the geometrical features of the reconstructed luminosity-distance relation. Using the recently released supernovae data by the Supernova Legacy Survey together with a phase space representation, we show that the reconstructed luminosity-distance curves best fitting the data correspond to a slightly varying dark energy density with the Universe expanding slightly slower than the $\Lambda \mathrm{CDM}$ model. However, the $\Lambda \mathrm{CDM}$ model fits the data at $1\sigma$ significance level and the fact that our best fitting luminosity-distance curve is lower than that of the corresponding $\Lambda \mathrm{CDM}$ model could be due to systematics. The transition from an accelerating to a decelerating expansion occurs at a redshift larger than $z=0.35$. Interpreting the dark energy as a minimally coupled scalar field we also reconstruct the scalar field and its potential. We constrain ${\Omega }_{m_0}$ using the baryon acoustic oscillation peak in the SDSS luminous red galaxy sample and find that the best fit is obtained with ${\Omega }_{m_0}=0.27$, in agreement with the CMB data.

Based on the chiral perturbation theory with the hidden local symmetry, we propose a methodology to calculate a part of the large $N_c$ corrections in the holographic QCD (HQCD). As an example, we apply the method to an HQCD model recently proposed by Sakai and Sugimoto. We show that the $\rho \mathrm{\text{−}}\pi \mathrm{\text{−}}\pi$ coupling is in good agreement with the experiment due to the $1/N_c$-subleading corrections.

We compute the cross section for $\chi \chi \to q\overline{q}g$ at order ${\alpha }_s^2/M_{\tilde{q}}^6$ arising from interference between the tree-level and loop-induced processes. This interference term is the same order in ${\alpha }_s$ as $\chi \chi \to gg$; for mass degenerate squarks $M_{{\tilde{q}}_R}=M_{{\tilde{q}}_L}=M_{\tilde{q}}$ we find $v_{\mathrm{rel}}{\sigma }_{\mathrm{int}}=[-2m_{\chi }^2/3M_{\tilde{q}}^2]v_{\mathrm{rel}}\sigma (\chi \chi \to gg)$.

An analysis of generating fermion masses via cubic couplings in $SO(10)$ grand unification with a unified Higgs sector is given. The new framework utilizes a single pair of vector-spinor representation $144+\overline{144}$ to break the gauge symmetry all the way to $SU(3{)}_C\times U(1{)}_{\mathrm{em}}$. Typically the matter-Higgs couplings in this framework are quartic and lead to naturally suppressed Yukawa couplings for the first two generations. Here we show that much larger third generation couplings naturally arise at the cubic level with additional matter in 10-plet and 45-plet representations of $SO(10)$. Thus the physical third generation is a mixture of 16, 10, and 45-plet representations while the remaining components become superheavy and are removed from the low energy spectrum. In this scenario it is possible to understand the heaviness of the top in a natural way since the analysis generates a hierarchy in the Yukawa couplings so that $h_t/h_b\gg 1$ where $h_t(h_b)$ are the top (bottom) Yukawa couplings. It is then possible to realize values of $\tan \beta$ as low as 2, which also helps to stabilize the proton.

We investigate quantitatively the extent to which having a primordial leptonic asymmetry $(n_{\nu }\ne n_{\overline{\nu }})$ relaxes the bounds on light sterile neutrinos imposed by BBN and LSS. We adopt a few assumptions that allow us to solve the neutrino evolution equations over a broad range of mixing parameters and asymmetries. For the general cases of sterile mixing with the electron or muon neutrino, we identify the regions that can be reopened. For the particular case of a LSND-like sterile neutrino, soon to be rejected or confirmed by MiniBooNE, we find that an asymmetry of the order of ${10}^{-4}$ is needed to lift the conflicts with cosmology.

We construct a class of charged, rotating solutions of $(n+1)$-dimensional Einstein-Maxwell-dilaton gravity with cylindrical or toroidal horizons in the presence of Liouville-type potentials and investigate their properties. These solutions are neither asymptotically flat nor (anti)-de Sitter. We find that these solutions can represent black brane, with inner and outer event horizons, an extreme black brane or a naked singularity provided the parameters of the solutions are chosen suitably. We also compute temperature, entropy, charge, electric potential, mass and angular momentum of the black brane solutions, and find that these quantities satisfy the first law of thermodynamics. We find a Smarr-type formula and perform a stability analysis by computing the heat capacity in the canonical ensemble. We find that the system is thermally stable when the coupling constant between the dilaton and matter field $\alpha \le 1$, while for $\alpha >1$ the system has an unstable phase. This shows that the dilaton field makes the solution unstable, while it is stable even in Lovelock gravity.

We compute the probability for quantum creation of an inflationary universe with and without a pair of black holes in a modified gravity. The action of the modified theory of gravity contains $\alpha R^2$ and $\delta R^{-1}$ terms in addition to a cosmological constant ($\Lambda$) in the Einstein-Hilbert action. The probabilities for the creation of universe with a pair of black holes have been evaluated considering two different kinds of spatial sections, one which accommodates a pair of black holes and the other without black hole. We adopt a technique prescribed by Bousso and Hawking to calculate the above creation probability in a semiclassical approximation using the Hartle-Hawking boundary condition. We note a class of new and physically interesting instanton solutions characterized by the parameters in the action. These instantons may play an important role in the creation of the early universe. We also note that the probability of creation of a universe with a pair of black holes is strongly suppressed with a positive cosmological constant when $\delta =\frac{4{\Lambda }^2}{3}$ for $\alpha >0$ but it is more probable for $\alpha <-\frac{1}{6\Lambda }$. In the modified gravity considered here instanton solutions are permitted even without a cosmological constant when one begins with a negative $\delta$.