We study Lunin-Maldacena deformations of cosmological backgrounds of $D=11$ supergravity which gives an easy way to generate solutions with nonzero 4-form flux starting from solutions of pure Einstein equations which possess at least three $U(1)$ isometries. We illustrate this on the vacuum S-brane solution from which the usual SM2-brane solution is obtained. Applying the method again, one either gets the recently found S-brane system where a contribution of the Chern-Simons term to field equations is nonzero or the $\mathrm{SM}2\perp \mathrm{SM}2(0)$ intersection, depending on which $U(1)$ directions are used during the process. Repeated usage of the procedure gives rise to configurations with several overlapping S-branes, some of which are new. We also employ this method to construct two more new solutions and make comments about accelerating cosmologies that follow from such deformed solutions after compactification to ($1+3$) dimensions.

In generic holographic QCD, we find that baryons are bound to form a nucleus, and that its radius obeys the empirically-known mass-number ($A$) dependence $r\propto A^{1/3}$ for large $A$. Our result is robust, since we use only a generic property of D-brane actions in string theory. We also show that nucleons are bound completely in a finite volume. Furthermore, employing a concrete holographic model (derived by Hashimoto, Iizuka, and Yi, describing a multibaryon system in the Sakai-Sugimoto model), the nuclear radius is evaluated as $\mathcal{O}(1)\times A^{1/3}[\mathrm{fm}]$, which is consistent with experiments.

The Higgs-strahlung process $e^{+}{e}^{-}\to ZH$ and pair production process $e^{+}{e}^{-}\to HH$ are studied in the framework of the minimal noncommutative (NC) standard model. In particular, the Feynman rules involving all orders of the noncommutative parameter $\theta$ are derived using reclusive formation of the Seiberg-Witten map. It is shown that the total cross section and angular distribution can be significantly affected because of space-time noncommutativity when the collision energy exceeds to 1 TeV. It is found that in each process, there is an optimal collision energy ($E_{\mathrm{oc}}$) for achieving the greatest noncommutative effect, and $E_{\mathrm{oc}}$ varies linearly with the NC scale ${\Lambda }_{\mathrm{NC}}$. A brief discussion on the process $e^{+}{e}^{-}\to {\mu }^{+}{\mu }^{-}$ is also given.

In this paper we calculate the vacuum expectation values of the stress-energy bitensor of a massive quantum scalar field with general coupling to $N$-dimensional Euclidean spaces and hyperbolic spaces which are Euclidean sections of the anti-de Sitter spaces. These correlators, also known as the noise kernel, act as sources in the Einstein-Langevin equations of stochastic gravity [B. L. Hu and E. Verdaguer, Living Rev. Relativity 11, 3 (2008).][B. L. Hu and E. Verdaguer, Classical Quantum Gravity 20, R1 (2003).] which govern the induced metric fluctuations beyond the mean-field dynamics described by the semiclassical Einstein equations of semiclassical gravity. Because these spaces are maximally symmetric the eigenmodes have analytic expressions which facilitate the computation of the zeta function [J. S. Dowker and R. Critchley, Phys. Rev. D 13, 224 (1976); J. S. DowkerR. Critchley, Phys. Rev. D 13, 3224 (1976).][S. W. Hawking, Commun. Math. Phys. 55, 133 (1977).]. Upon taking the second functional variation of the generalized zeta function introduced in [N. G. Phillips and B. L. Hu, Phys. Rev. D 55, 6123 (1997).] we obtain the correlators of the stress tensor for these two classes of spacetimes. Both the short and the large geodesic distance limits of the correlators are presented for dimensions up to 11. We mention current research problems in early universe cosmology, black hole physics and gravity-fluid duality where these results can be usefully applied to.

We reproduce the two-body gravitational conservative dynamics at third post-Newtonian order for spinless sources by using the effective field theory methods for the gravitationally bound two-body system, proposed by Goldberger and Rothstein. This result has been obtained by automatizing the computation of Feynman amplitudes within a Mathematica algorithm, paving the way for higher-order computations not yet performed by traditional methods.

We analyze the properties of circular orbits of test particles on the equatorial plane of a rotating central mass whose gravitational field is described by the Kerr spacetime. For rotating black holes and naked singularities we explore all the spatial regions where circular orbits can exist and analyze the behavior of the energy and the angular momentum of the corresponding test particles. In particular, we find all the radii at which a test particle can have zero angular momentum due to the repulsive gravity effects generated by naked singularities. We classify all the stability zones of circular orbits. It is shown that the geometric structure of the stability zones of black holes is completely different from that of naked singularities.

We considered the behavior of Dirac fermion modes in the background of a Euclidean dilaton black hole with an Abelian Higgs vortex passing through it. Fermions were coupled to the fields due to the superconducting string model. The case of nonextremal and extremal charged black holes in the theory with an arbitrary coupling constant between the dilaton field and $U(1)$-gauge field was considered. We elaborated the cases of zero and nonzero Dirac fermion modes. One finds evidence that the system under consideration can support fermion fields acting like a superconducting hair on a black hole in the sense that a nontrivial spinor field configuration can be carried by a Euclidean spherically symmetric charged dilaton black hole. It was revealed that the localization of Dirac fermion modes depended on the cosmic string winding number and the value of black hole surface gravity.

We construct Hořava-Lifshitz gravities that are invariant under anisotropic Weyl scaling. This construction is based on an extension of the group of symmetries of healthy extended Hořava-Lifshitz gravity and restricted-foliation-preserving Diff invariant Hořava-Lifshitz gravity. We find their Hamiltonian formulation and determine their constraint structure.

In order to annihilate in the early Universe to levels well below the measured dark matter density, asymmetric dark matter must possess large couplings to the standard model. In this paper, we consider effective operators which allow asymmetric dark matter to annihilate into quarks. In addition to a bound from requiring sufficient annihilation, the energy scale of such operators can be constrained by limits from direct detection and monojet searches at colliders. We show that the allowed parameter space for these operators is highly constrained, leading to nontrivial requirements that any model of asymmetric dark matter must satisfy.

The Kim-Nilles mechanism relates the $\mu$ term with the axion scale $f_a$, leading to the axino-Higgsino-Higgs Yukawa coupling of order $\mu /f_a$. This can bring a dangerous thermal production of axinos. If the axino is stable, its mass has to be as small as $\mathcal{O}(0.1\mathrm{keV})$, or the reheat temperature should be lower than $\mathcal{O}(10\mathrm{GeV})$ taking the lower axion scale ${10}^{10}\mathrm{GeV}$ in order not to overclose the Universe. If the axino decays to a neutralino, the overproduced neutralinos can reannihilate appropriately to saturate the observed dark matter density if the annihilation rate is of order ${10}^{-8}{\mathrm{GeV}}^{-2}$ for the axion scale larger than about ${10}^{11}\mathrm{GeV}$. Thus, a light Higgsino-like lightest supersymmetric particle with a sizable bino mixture becomes a good dark matter candidate whose nucleonic cross section is larger than about ${10}^{-45}{\mathrm{cm}}^2$.

Recent cosmic ray (CR) experiments discovered that the CR spectra experience a remarkable hardening for rigidity above several hundred GV. We propose that this is caused by the superposition of the CR energy spectra of many sources that have a dispersion in the injection spectral indices. Adopting similar parameters as those of supernova remnants derived from the Fermi $\gamma$-ray observations, we can reproduce the observational CR spectra of different species well. This may be interpreted as evidence to support the supernova remnant origin of CRs below the knee. We further propose that the same mechanism may explain the “ankle” of the ultra high energy CR spectrum.

We propose helium-4 spallation processes induced by long-lived stau in supersymmetric standard models, and investigate an impact of the processes on light elements abundances. We show that, as long as the phase space of helium-4 spallation processes is open, they are more important than stau-catalyzed fusion and hence constrain the stau property.

We propose a novel framework in which the observed baryon and dark matter abundances are simultaneously generated via the Affleck-Dine mechanism. In its simplest realization, Affleck-Dine cogenesis is accomplished by a single superpotential operator and its $A$-term counterpart. These operators explicitly break $B-L$ and $X$, the dark matter number, to the diagonal $B-L+X$. In the early universe these operators stabilize supersymmetric flat directions carrying nonzero $B-L$ and $X$, and impart the requisite $CP$ violation for asymmetry generation. Because $B-L+X$ is preserved, the resulting $B-L$ and $X$ asymmetries are equal and opposite, though this precise relation may be relaxed if $B-L$ and $X$ are violated separately by additional operators. Our dark matter candidate is stabilized by $R$ parity and acquires an asymmetric abundance due to its nonzero $X$ number. For a dark matter mass of order a few GeV, one naturally obtains the observed ratio of energy densities today, ${\Omega }_{\mathrm{DM}}/{\Omega }_B\sim 5$. These theories typically predict macroscopic lifetimes for the lightest observable supersymmetric particle as it decays to the dark matter.

We show that a $Z^{\prime }$ with suppressed couplings to the electron compared to the $Z$-boson, with couplings to the $b$-quark, and with a mass close to the mass of the $Z$-boson, provides an excellent fit to forward-backward asymmetry of the $b$-quark and $R_b$ measured on the $Z$-pole and $\pm 2\mathrm{GeV}$ off the $Z$-pole, and to $A_e$ obtained from the measurement of left-right asymmetry for hadronic final states. It also leads to a significant improvement in the total hadronic cross section on the $Z$-pole and $R_b$ measured at energies above the $Z$-pole. In addition, with a proper mass, it can explain the excess of $Zb\overline{b}$ events at LEP in the 90–105 GeV region of the $b\overline{b}$ invariant mass.

We investigate a simple 5D extension of the Minimal Supersymmetric (SUSY) Standard Model (SM) that is combined with the bulk matter Randall-Sundrum (RS) model, which gives a natural explanation the Yukawa coupling hierarchy. In this model, matter and gauge superfields reside in the 5D bulk while a SUSY breaking sector and the Higgs doublet superfields are localized on the infrared brane. The Yukawa coupling hierarchy in SM can be naturally explained through the wavefunction localization of the matter superfields. While sparticles obtain their flavor-blind soft SUSY breaking masses dominantly from the gaugino-mediated SUSY breaking, flavor-violating soft terms arise through the gravity-mediated SUSY breaking which are controlled by the wavefunction localization of the matter superfields. This structure of the model allows us to predict the sparticle mass spectrum including flavor-violating terms. We first explicitly determine the 5D disposition of matter superfields from the low-energy experimental data on SM fermion masses, CKM matrix and the neutrino oscillation parameters. Then, we calculate particle mass spectra and estimate the effects of the flavor-violating soft terms, which should be compared with the current experimental constraints. With gravitino being the lightest sparticle (LSP), the next-to-LSP, which is long-lived, is predicted most likely to be either singlet smuonlike or selectronlike. The model can be tested at collider experiments through flavor-violating processes involving sparticles. The flavor structure among sparticle, once observed, gives us a clue to deep understanding of the origin of Yukawa coupling hierarchy.

The minimal prescription procedure is applied to tame the Landau pole singularities of resummed formulae for heavy quark decays. Effects of the final quark mass are taken into account. Explicit expressions are obtained for the $t\to b$ and $b\to c$ transitions for both the frozen coupling approximation and in the QCD running coupling case.

We compute the energy of a static hybrid, i.e., of a hybrid quarkonium with static quark and antiquark, at short distances in $D=4,3$, dimensions. The soft contribution to this energy is the static potential of a color-octet quark-antiquark pair at short distances, which is known at two loops for arbitrary $D$. We have checked this expression employing thermal field theory methods. Using the effective field theory potential nonrelativistic QCD we calculate the ultrasoft contributions to the hybrid (and singlet) static energy at the two-loop level. We then present new results for the static hybrid energy/potential and the hybrid decay width in three and four dimensions. Finally we comment on the meaning of the perturbative results in two space-time dimensions, where the hybrid does not exist.

Three-particle correlations in quark and gluon jets are computed for the first time in perturbative QCD. We give results in the double logarithmic approximation and the modified leading logarithmic approximation. In both resummation schemes, we use the formalism of the generating functional and solve the evolution equations analytically from the steepest descent evaluation of the one-particle distribution. We thus provide a further test of the local parton hadron duality and make predictions for the LHC.

There exist experimental hints from the $B$ sector for $CP$ violation beyond the standard model (SM) paradigm. An anomalous dimuon asymmetry was reported by the D0 Collaboration, while tension exists between $B\to \tau \nu$ and $S_{\psi K}$. These measurements, disfavoring the SM at the $\sim 3\sigma$ level, can be explained by new physics in both $B_d^0-{\overline{B}}_d^0$ and $B_s^0-{\overline{B}}_s^0$ mixing, arising from (1) new bosonic degrees of freedom at or near the electroweak scale, and (2) new, large $CP$-violating phases. These two new physics ingredients are precisely what is required for electroweak baryogenesis to work in an extension of the SM. We show that a simple two Higgs doublet model with top-charm flavor violation can explain the $B$ anomalies and the baryon asymmetry of the Universe. Moreover, the presence of a large relative phase in the top-charm Yukawa coupling, favored by $B_{d,s}^0\mathrm{\text{−}}{\overline{B}}_{d,s}^0$ mixing, weakens constraints from ${ϵ}_K$ and $b\to s\gamma$, allowing for a light charged Higgs mass of $\mathcal{O}(100\mathrm{GeV})$.

A relativistic constituent quark model is applied to the $\gamma N\to N(1535)$ transition. The $N(1535)$ wave function is determined by extending the covariant spectator quark model, previously developed for the nucleon, to the $S_{11}$ resonance. The model allows us to calculate the valence quark contributions to the $\gamma N\to N(1535)$ transition form factors. Because of the nucleon and $N(1535)$ structure the model is valid only for $Q^2>2.3{\mathrm{GeV}}^2$. The results are compared with the experimental data for the electromagnetic form factors $F_1^{*}$ and $F_2^{*}$ and the helicity amplitudes $A_{1/2}$ and $S_{1/2}$, at high $Q^2$.