According to heavy-meson chiral perturbation theory, the vector form factor $f_{+}(q^2)$ of exclusive semileptonic decay $B\to \pi \ell \nu$ is closely related, at least in the soft-pion region (i.e., $q^2\sim (m_B-m_{\pi }{)}^2$), to the strong coupling $g_{B^{*}B\pi }$ or the normalized coupling $\widehat{g}$. Combining the precisely measured $q^2$ spectrum of $B\to \pi \ell \nu$ decay by the BABAR and Belle collaborations with several parametrizations of the form factor $f_{+}(q^2)$, we can extract these couplings from the residue of the form factor at the $B^{*}$ pole, which relies on an extrapolation of the form factor from the semileptonic region to the unphysical point $q^2=m_{B^{*}}^2$. Comparing the extracted values with the other experimental and theoretical estimates, we can test these various form-factor parametrizations, which differ from each other by the amount of physical information embedded in. It is found that the extracted values based on the Bećirević-Kaidalov, Ball-Zwicky and Bourrely-Caprini-Lellouch parametrizations are consistent with each other and roughly in agreement with the other theoretical and lattice estimates, while the Boyd-Grinstein-Lebed ansatz, featured by a spurious, unwanted pole at the threshold of the cut, gives a neatly larger value.

We discuss in detail top quark polarization in above-threshold $(t\overline{t})$ production at a polarized linear $e^{+}{e}^{-}$ collider. We pay particular attention to the minimization and maximization of the polarization of the top quark by tuning the longitudinal polarization of the $e^{+}$ and $e^{-}$ beams. The polarization of the top quark is calculated in full next-to-leading order QCD. We also discuss the beam polarization dependence of the longitudinal spin-spin correlations of the top and antitop quark spins.

We extract parton distribution functions (PDFs) and structure functions from recent experimental data of polarized lepton–deeply inelastic scattering (DIS) on nucleons at next-to-leading order (NLO) quantum chromodynamics. We apply the Jacobi polynomial method to the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) evolution as this is numerically efficient. Having determined the polarized proton and neutron spin structure, we extend this analysis to describe ${}^3\mathrm{He}$ and ${}^3\mathrm{H}$ polarized structure functions, as well as various sum rules. We compare our results with other analyses from the literature.

Here we report that Elko (for Eigenspinoren des Ladungskonjugationsoperators) breaks Lorentz symmetry in a rather subtle and unexpected way by containing a “hidden” preferred direction. Along this preferred direction, a quantum field based on Elko enjoys locality. In the form reported here, Elko offers a mass dimension one fermionic dark matter with a quartic self-interaction and a preferred axis of locality. The locality result crucially depends on a judicious choice of phases.

We derive a general expression for the large-scale halo bias, in theories with a scale-dependent linear growth, using the excursion set formalism. Such theories include modified-gravity models, and models in which the dark energy clustering is non-negligible. A scale dependence is imprinted in both the formation and evolved biases by the scale-dependent growth. Mergers are accounted for in our derivation, which thus extends earlier work which focused on passive evolution. There is a simple analytic form for the bias for those theories in which the nonlinear collapse of perturbations is approximately the same as in general relativity. As an illustration, we apply our results to a simple Yukawa modification of gravity, and use Sloan Digital Sky Survey measurements of the clustering of luminous red galaxies to constrain the theory’s parameters.

The important issue of the magnetic component of gravitational waves (GWs) has been considered in various papers in the literature. From such analyses, it has been found that such a magnetic component becomes particularly important in the high-frequency portion of the frequency range of ground based interferometers for GWs which arises from standard general theory of relativity (GTR). Recently, such a magnetic component has been extended to GWs arising from scalar-tensor gravity (STG) too. After a review of some important issues on GWs in STG, in this paper we reanalyze the magnetic component in the framework of STG from a different point of view, by correcting an error in a previous paper and by releasing a more precise response function. In this way, we also show that if one neglects the magnetic contribution considering only the low-frequency approximation of the electric contribution, an important part of the signal could be, in principle, lost. The determination of a more precise response function for the magnetic contribution is important also in the framework of the possibility of distinguishing other gravitational theories from GTR. At the conclusion of this paper, an expansion of the main results is also shown in order to recall the presence of the magnetic component in GTR too.

The decay modes of the type $B\to \pi \pi$ are dynamically different. For the case ${\overline{B}}_d^0\to {\pi }^{+}{\pi }^{-}$ there is a substantial factorized contribution which dominates. In contrast, the decay mode ${\overline{B}}_d^0\to {\pi }^0{\pi }^0$ has a small factorized contribution, being proportional to a small Wilson coefficient combination. However, for the decay mode ${\overline{B}}_d^0\to {\pi }^0{\pi }^0$ there is a sizeable nonfactorizable (color suppressed) contribution due to soft (long distance) interactions, which dominate the amplitude. We estimate the branching ratio for the mode ${\overline{B}}_d^0\to {\pi }^0{\pi }^0$ in the heavy quark limit for the $b$ quark. In order to estimate color suppressed contributions we treat the energetic light ($u$, $d$, $s$) quark within a variant of Large Energy Effective Theory combined with a recent extension of chiral quark models in terms of model- dependent gluon condensates. We find that our calculated color suppressed amplitude is suppressed by a factor of order ${\Lambda }_{\mathrm{QCD}}/m_b$ with respect to the factorizable amplitude, as it should according to QCD-factorization. Further, for reasonable values of the constituent quark mass and the gluon condensate, the calculated nonfactorizable amplitude for ${\overline{B}}_d^0\to {\pi }^0{\pi }^0$ can easily accommodate the experimental value. Unfortunately, the color suppressed amplitude is very sensitive to the values of these model-dependent parameters. Therefore fine-tuning is necessary in order to obtain an amplitude compatible with the experimental result for ${\overline{B}}_d^0\to {\pi }^0{\pi }^0$. A possible link to the triangle anomaly is discussed.

We analyze the LSND, KARMEN, and MiniBooNE data on short-baseline ${\overline{\nu }}_{\mu }\to {\overline{\nu }}_e$ oscillations and the data on short-baseline ${\overline{\nu }}_e$ disappearance obtained in the Bugey-3 and CHOOZ reactor experiments in the framework of $3+1$ antineutrino mixing, taking into account the MINOS observation of long-baseline ${\overline{\nu }}_{\mu }$ disappearance and the KamLAND observation of very-long-baseline ${\overline{\nu }}_e$ disappearance. We show that the fit of the data implies that the short-baseline disappearance of ${\overline{\nu }}_{\mu }$ is relatively large. We obtain a prediction of an effective amplitude ${sin}^{2}2{\vartheta }_{\mu \mu }\gtrsim 0.1$ for short-baseline ${\overline{\nu }}_{\mu }$ disappearance generated by $0.2\lesssim \Delta m^2\lesssim 1{\mathrm{eV}}^2$, which could be measured in future experiments.

We study numerically a 5D hybrid model which incorporates a split fermion scenario and bulk neutrinos. We perform a Monte Carlo analysis of the model in order to find the regions in the parameter space allowing for the realization of the leptogenesis. We find that higher order Yukawa terms must be included in order for the model to produce a $CP$ violation and net baryon number sufficient for the creation of the observed baryon asymmetry of the Universe.

We propose a natural scenario for the cosmological inflation with the nonminimal coupling term invoking compact hyperbolic extra dimensions. Thanks to the unique mathematical properties of compact hyperbolic space, the large volume of extra dimensions, which provides a natural understanding of the proper size of couplings, does not necessarily accompany with the low Kaluza-Klein scale so that the model allows a single field inflation with a scale around ${10}^{13}\mathrm{GeV}$. The model fulfills all the observed data and predicts a sizable gravitational perturbation, $r\simeq 3\times {10}^{-3}$.

Motivated by recent developments in the understanding of the connection between five branes on resolved geometries and the corresponding generalizations of complex deformations in the context of the warped resolved deformed conifold, we consider the construction of five branes solutions on the resolved cone over $Y^{p,q}$ spaces. We establish the existence of supersymmetric five branes solutions wrapped on two-cycles of the resolved cone over $Y^{p,q}$ in the probe limit. We then use calibration techniques to begin the construction of fully back-reacted five branes; we present an Ansatz and the corresponding equations of motion. Our results establish a detailed framework to study back-reacted five branes wrapped on the resolved cone over $Y^{p,q}$ and as a first step we find explicit solutions and construct an asymptotic expansion with the expected properties.

We obtain a supersymmetric three family chiral SU(6) grand unification model with the global family symmetry $\mathrm{SU}(3{)}_{\mathrm{family}}$ from the use of F-theory. This model has nice features, for instance, all the fermion masses are reasonably generated and result in only one pair of Higgs doublets, giving the doublet-triplet splitting from the family symmetry $\mathrm{SU}(3{)}_{\mathrm{family}}$. The proton hexality is also realized toward the proton stability problem. The model also has a room to fit the three gauge couplings using the F-theory flux idea and we obtain the upper bound of proton lifetime in the ${10}^{36–37}\mathrm{yr}$ region.

We characterize the one-loop amplitudes for $\mathcal{N}=6$ and $\mathcal{N}=4$ supergravity in four dimensions. For $\mathcal{N}=6$ we find that the one-loop $n$-point amplitudes can be expanded in terms of scalar box and triangle functions only. This simplification is consistent with a loop momentum power count of $n-3$, which we would interpret as being $n+4$ for gravity with a further $-7$ from the $\mathcal{N}=6$ superalgebra. For $\mathcal{N}=4$ we find that the amplitude is consistent with a loop momentum power count of $n$, which we would interpret as being $n+4$ for gravity with a further $-4$ from the $\mathcal{N}=4$ superalgebra. In contrast to previous studies we find that the $\mathcal{N}=4$ amplitudes contain noncut-constructible rational terms.

We investigate the effects of pseudoscalar-photon mixing on electromagnetic radiation in the presence of correlated extragalactic magnetic fields. We model the Universe as a collection of magnetic domains and study the propagation of radiation through them. This leads to correlations between Stokes parameters over large scales and consistently explains the observed large-scale alignment of quasar polarizations at different redshifts within the framework of the big bang model.

We derive the exact analytical solution of the linear structure growth rate in $\Lambda \mathrm{CDM}$ cosmology with flat or curved geometry, under the Newtonian gauge. Unlike the well known solution under the Newtonian limit [D. J. Heath, Mon. Not. R. Astron. Soc. 179, 351 (1977)], our solution takes all general relativistic corrections into account and is hence valid at both the sub- and superhorizon scales. With this exact solution, we evaluate cosmological impacts induced by these relativistic corrections. (1) General relativistic corrections alter the density growth from $z=100$ to $z=0$ by 10% at $k=0.01h/\mathrm{Mpc}$ and the impact becomes stronger toward larger scales. We caution the readers that the overdensity is not gauge invariant and the above statement is restrained to the Newtonian gauge. (2) Relativistic corrections introduce a $k^{-2}$ scale dependence in the density fluctuation. It mimics a primordial non-Gaussianity of the local type with $f_{\mathrm{NL}}^{\mathrm{local}}\sim 1$. This systematical error may become non-negligible for future all sky deep galaxy surveys. (3) Cosmological simulations with box size greater than 1 Gpc are also affected by these relativistic corrections. We provide a postprocessing recipe to correct for these effects. (4) These relativistic corrections affect the redshift distortion. However, at redshifts and scales relevant to redshift distortion measurements, such effect is negligible.

We consider current observational constraints on the electromagnetic charge of dark matter. The velocity dependence of the scattering cross section through the photon gives rise to qualitatively different constraints than standard dark matter scattering through massive force carriers. In particular, recombination epoch observations of dark matter density perturbations require that $ϵ$, the ratio of the dark matter to electronic charge, is less than ${10}^{-6}$ for $m_X=1\mathrm{GeV}$, rising to $ϵ<{10}^{-4}$ for $m_X=10\mathrm{TeV}$. Though naively one would expect that dark matter carrying a charge well below this constraint could still give rise to large scattering in current direct detection experiments, we show that charged dark matter particles that could be detected with upcoming experiments are expected to be evacuated from the Galactic disk by the Galactic magnetic fields and supernova shock waves and hence will not give rise to a signal. Thus dark matter with a small charge is likely not a source of a signal in current or upcoming dark matter direct detection experiments.

A method is developed for dealing with ultraviolet divergences in calculations of cosmological correlations, which does not depend on dimensional regularization. An extended version of the WKB approximation is used to analyze the divergences in these calculations, and these divergences are controlled by the introduction of Pauli-Villars regulator fields. This approach is illustrated in the theory of a scalar field with arbitrary self-interactions in a fixed flat-space Robertson-Walker metric with arbitrary scale factor $a(t)$. Explicit formulas are given for the counterterms needed to cancel all dependence on the regulator properties, and an explicit prescription is given for calculating finite regulator-independent correlation functions. The possibility of infrared divergences in this theory is briefly considered.

We consider the production of primordial micro black holes (MBH) remnants in the early Universe. These objects induce the Universe to be in a matter-dominated era before the onset of inflation. Effects of such an epoch on the CMB power spectrum are discussed and computed both analytically and numerically. By comparison with the latest observational data from the WMAP collaboration, we find that our model appears to explain the quadrupole anomaly of the CMB power spectrum.

Recent advances in holography have led to the formulation of fluid-gravity duality, a remarkable connection between the hydrodynamics of certain strongly coupled media and dynamics of higher dimensional black holes. This paper introduces a correspondence between phenomenologically defined entropy currents in relativistic hydrodynamics and “generalized horizons” of near-equilibrium black objects in a dual gravitational description. A general formula is given, expressing the divergence of the entropy current in terms of geometric objects which appear naturally in the gravity dual geometry. The proposed definition is explicitly covariant with respect to boundary diffeomorphisms and reproduces known results when evaluated for the event horizon.

We study phenomena predicted by a renormalizable, $CPT$ invariant extension of the standard model that contains higher-dimensional operators and violates Lorentz symmetry explicitly at energies greater than some scale ${\Lambda }_L$. In particular, we consider the Cherenkov radiation in vacuo. In a rather general class of dispersion relations, there exists an energy threshold above which radiation is emitted. The threshold is enhanced in composite particles by a sort of kinematic screening mechanism. We study the energy loss and compare the predictions of our model with known experimental bounds on Lorentz violating parameters and observations of ultrahigh-energy cosmic rays. We argue that the scale of Lorentz violation ${\Lambda }_L$ (with preserved $CPT$ invariance) can be smaller than the Planck scale, actually as small as ${10}^{14}–{10}^{15}\mathrm{GeV}$. Our model also predicts the Cherenkov radiation of neutral particles.