We show that the presence of a $\rho \sim r^{-3/2}$ dark matter overdensity can be robustly predicted at the center of any galaxy old enough to have grown a power-law density cusp in the stars via the Bahcall-Wolf mechanism. Using both Fokker-Planck and direct $N$-body integrations, we demonstrate collisional generation of these dark matter “crests” (collisionally regenerated structures) even in the extreme case that the density of both stars and dark matter were previously lowered by slingshot ejection from a binary supermassive black hole. The time scale for collisional growth of the crest is approximately the two-body relaxation time as defined by the stars, which is $\lesssim 10\mathrm{Gyr}$ at the centers of stellar spheroids with luminosities $L\lesssim {10}^{9.5}{L}_{\odot }$, including the bulge of the Milky Way. The presence of crests can robustly be predicted in such galaxies, unlike the steeper enhancements, called “spikes,” produced by the adiabatic growth of black holes. We discuss special cases where the prospects for detecting dark matter annihilations from the centers of galaxy halos are significantly affected by the formation of crests.

A recently proposed novel technique for the detection of cosmic rays with arrays of Imaging Atmospheric Cherenkov Telescopes is applied to data from the High Energy Stereoscopic System (H.E.S.S.). The method relies on the ground-based detection of Cherenkov light emitted from the primary particle prior to its first interaction in the atmosphere. The charge of the primary particle (Z) can be estimated from the intensity of this light, since it is proportional to ${\mathrm{Z}}^2$. Using H.E.S.S. data, an energy spectrum for cosmic-ray iron nuclei in the energy range 13–200 TeV is derived. The reconstructed spectrum is consistent with previous direct measurements and is one of the most precise so far in this energy range.

We explicitly calculate the contribution to Higgs production at the LHC from the interference between gluon fusion and weak vector boson fusion, and compare it to the pure QCD and pure electroweak result. While the effect is small at tree level, we speculate it will be significantly enhanced by loop effects.

We compare current-current correlators in lattice gauge calculations with correlators in different potential models, for a pseudoscalar charmonium in the quark-gluon plasma. An important ingredient in the evaluation of the current-current correlator in the potential model is the basic principle that, out of the set of continuum states, only resonance states and Gamow states with lifetimes of sufficient magnitudes can propagate as composite objects and can contribute to the current-current correlator. When the contributions from the bound states and continuum states are properly treated, the potential model current-current correlators obtained with the potential proposed by Wong [Phys. Rev. C 72, 034906 (2005)] are consistent with the lattice gauge correlators. The proposed potential model thus gains support to be a useful tool to complement lattice gauge calculations for the study of $Q\overline{Q}$ states at high temperatures.

We calculate one-loop renormalization factors for heavy-light bilinears as well as four-fermion operators relevant for $B^0-{\overline{B}}^0$ mixing calculations on the lattice. We use the static approximation for heavy quarks and the domain-wall formulation for light quarks. We present results for different choices of improved gauge action.

In this article, we take the point of view that the charmed mesons $D_{s0}(2317)$ and $D_{s1}(2460)$ with the spin-parity $0^{+}$ and $1^{+}$ respectively are the conventional $c\overline{s}$ states, and calculate the strong coupling constants $G_S$(for $⟨D_s^{*}\varphi |D_{s0}⟩$) and $G_A$(for $⟨D_s\varphi |D_{s1}⟩$) in the framework of the light-cone QCD sum rules approach. The strong coupling constants $G_S$ and $G_A$ are related to the basic parameter $\widehat{\mu }$ in the heavy quark effective Lagrangian, the numerical value is larger than the existing estimation. With the assumption of the vector meson dominance of the intermediate $\varphi (1020)$, we study the radiative decays $D_{s0}\to D_s^{*}\gamma$ and $D_{s1}\to D_s\gamma$.

We study $J/\psi$ photoproduction via the fusion and fragmentation mechanisms at the HERA Collider within the frameworks of the collinear parton model and the quasi-multi-Regge kinematics approach using the factorization formalism of nonrelativistic QCD at leading order in the strong coupling constant ${\alpha }_s$ and the relative velocity $v$ of the bound quarks. It is shown that the fusion production mechanism dominates over the fragmentation production mechanism at the all relevant $J/\psi$ transverse momenta. The $J/\psi$ meson $p_T$ spectra in the fragmentation and fusion production at the asymptotilally large $p_T$ have equal slopes in the quasi-multi-Regge kinematics approach, opposite the collinear parton model.

We calculate the branching ratio of ${\overline{B}}^0\to {\Lambda }_c^{+}\overline{p}$ in the PQCD approach. Most previous model calculations obtained branching ratios significantly larger than experimental data. We find that the predicted branching ratio for $\mathrm{BR}({\overline{B}}^0\to {\Lambda }_c^{+}\overline{p})$ in the PQCD approach can vary over a range of $(2.3\sim 5.1)\times {10}^{-5}$ with the largest uncertainty coming from the parameters in the wave function of ${\Lambda }_c$. With the favored values for the parameters in the ${\Lambda }_c^{+}$ wave function, $\beta =1\mathrm{GeV}$ and $m_q=0.3\mathrm{GeV}$, the branching ratio is about $2.3\times {10}^{-5}$ which is satisfactorily consistent with the value measured by experiments.

The high scale mixing unification hypothesis recently proposed by three of us (R. N. M., M. K. P. and G. R.) states that if at the seesaw scale the quark and lepton mixing matrices are equal, then for quasidegenerate neutrinos radiative corrections can lead to large solar and atmospheric mixings and small reactor angle at the weak scale in agreement with data. Evidence for quasidegenerate neutrinos could, within this framework, be interpreted as being consistent with quark-lepton unification at high scale. In the current work, we extend this model to show that the hypothesis works quite successfully in the presence of $CP$-violating phases (which were set to zero in the first paper). In the case where the Pontecorvo-Maki-Nakagawa-Sakata matrix is identical to the Cabibbo-Kobayashi-Maskawa quark-mixing matrix at the seesaw scale, with a Dirac phase but no Majorana phase, the low energy Dirac phase is predicted to be ($\simeq 0.3°$) and leptonic $CP$-violation parameter $J_{CP}\simeq (4-8)\times {10}^{-5}$ and ${\theta }_{13}=3.5°$. If on the other hand, the Pontecorvo-Maki-Nakagawa-Sakata matrix is assumed to also have non-negligible Majorana phase(s) initially, the resulting theory damps radiative magnification phenomenon for a large range of parameters but nevertheless has enough parameter space to give the two necessary large neutrino mixing angles. In this case, one has ${\theta }_{13}=3.5°–10°$ and $|J_{CP}|$ as large as 0.02–0.04 which are accessible to long baseline neutrino oscillation experiments.

We consider the level-crossing problem in a three-level system with nonlinearly time-varying Hamiltonian (time-dependence $t^{-3}$). We study the validity of the so-called independent crossing approximation in the Landau-Zener model by making comparison with results obtained numerically in the density matrix approach. We also demonstrate the failure of the so-called “nearest zero” approximation of the Landau-Zener level-crossing probability integral.

We present a measurement of the hadronic invariant mass squared ($M_X^2$) spectrum in charmed semileptonic $B$ meson decays $B\to X_c\ell \nu$ based on $140{\mathrm{fb}}^{-1}$ of Belle data collected near the ${\rm Y}(4S)$ resonance. We determine the first, the second central, and the second noncentral moments of this spectrum for lepton energy thresholds ranging between 0.7 and 1.9 GeV. Full correlations between these measurements are evaluated.

In light-front dynamics, the regularization of amplitudes by traditional cutoffs imposed on the transverse and longitudinal components of particle momenta corresponds to restricting the integration volume by a nonrotationally invariant domain. The result depends not only on the size of this domain (i.e., on the cutoff values), but also on its orientation determined by the position of the light-front plane. Explicitly covariant formulation of light-front dynamics allows us to parametrize the latter dependence in a very transparent form. If we decompose the regularized amplitude in terms of independent invariant amplitudes, extra (nonphysical) terms should appear, with spin structures which explicitly depend on the orientation of the light-front plane. The number of form factors, i.e., the coefficients of this decomposition, therefore also increases. The spin-$1/2$ fermion self-energy is determined by three scalar functions, instead of the two standard ones, while for the elastic electromagnetic vertex the number of form factors increases from two to five. In the present paper we calculate perturbatively all these form factors in the Yukawa model. Then we compare the results obtained in the two following ways: (i) by using the light-front dynamics graph technique rules directly; (ii) by integrating the corresponding Feynman amplitudes in terms of the light-front variables. For each of these methods, we use two types of regularization: the transverse and longitudinal cutoffs, and the Pauli-Villars regularization. In the latter case, the dependence of amplitudes on the light-front plane orientation vanishes completely provided enough Pauli-Villars subtractions are made.

The Dyson-Schwinger equations arising from minimizing the vacuum energy density in the Hamiltonian approach to Yang-Mills theory in Coulomb gauge are solved numerically. A new solution is presented which gives rise to a strictly linearly rising static quark potential and whose existence was previously observed in the infrared analysis of the Dyson-Schwinger equations. For the new solution we also present the static quark potential and calculate the running coupling constant from the ghost-gluon vertex.

We consider a locally supersymmetric theory where the Planck mass is replaced by a dynamical superfield. This model can be thought of as the minimal supersymmetric extension of the Brans-Dicke theory (MSBD). The motivation that underlies this analysis is the research of possible connections between dark energy models based on Brans-Dicke-like theories and supersymmetric dark matter scenarios. We find that the phenomenology associated with the MSBD model is very different compared to the one of the original Brans-Dicke theory: the gravitational sector does not couple to the matter sector in a universal metric way. This feature could make the minimal supersymmetric extension of the BD idea phenomenologically inconsistent.

Recent astrophysical observations indicate that the proton-electron mass ratio and the fine structure constant have gone through nontrivial time evolution. We discuss their time variation in the context of a dilaton runaway scenario with gauge coupling unification at the string scale $M_{\mathrm{s}}$. We show that the choice of adjustable parameters allows them to fit the same order magnitude of both variations and their (opposite) signs in such a scenario.

We investigate homogeneous and isotropic oscillating cosmologies with multiple fluid components. Transfer of energy between these fluids is included in order to model the effects of nonequilibrium behavior on closed universes. We find exact solutions which display a range of new behaviors for the expansion scale factor. Detailed examples are studied for the exchange of energy from dust or a scalar field into radiation. We show that, contrary to expectation, it is unlikely that such models can offer a physically viable solution to the flatness problem.

Recently the branching ratios for $B^{+}\to K^{+}{\overline{K}}^0$ and $B^0\to K^0{\overline{K}}^0$ have been measured. Data indicate that the annihilation amplitudes in these decays are not zero. A nonzero annihilation amplitude plays an important role in $CP$ violation for $B^{+}\to {\pi }^{+}{K}^0$, $K^{+}{\overline{K}}^0$. Using the measured branching ratios for these decays, we show that there is an absolute bound of 5% for the size of $CP$ asymmetry in $B^{+}\to {\pi }^{+}{K}^0$ from a relation between the amplitudes of these decays. The size of $CP$ asymmetry in $B^{+}\to K^{+}{\overline{K}}^0$ can, however, be as large as 90%. Future experimental data will test these predictions.

Parametrized field theory (PFT) is free field theory on flat spacetime in a diffeomorphism invariant disguise. It describes field evolution on arbitrary (and in general, curved) foliations of the flat spacetime instead of only the usual flat foliations, by treating the “embedding variables” which describe the foliation as dynamical variables to be varied in the action in addition to the scalar field. A formal Dirac quantization turns the constraints of PFT into functional Schrödinger equations which describe evolution of quantum states from an arbitrary Cauchy slice to an infinitesimally nearby one. This formal Schrödinger picture-based quantization is unitarily equivalent to the standard Heisenberg picture-based Fock quantization of the free scalar field if scalar field evolution along arbitrary foliations is unitarily implemented on the Fock space. Torre and Varadarajan (TV) showed that for generic foliations emanating from a flat initial slice in spacetimes of dimension greater than 2, evolution is not unitarily implemented, thus implying an obstruction to Dirac quantization. We construct a Dirac quantization of PFT, unitarily equivalent to the standard Fock quantization, using techniques from loop quantum gravity (LQG) which are powerful enough to supercede the no-go implications of the TV results. The key features of our quantization include an LQG type representation for the embedding variables, embedding-dependent Fock spaces for the scalar field, an anomaly free representation of (a generalization of) the finite transformations generated by the constraints, and group averaging techniques. The difference between the $1+1$-dimensional case and the case of higher spacetime dimensions is that for the latter, only finite gauge transformations are defined in quantum theory, not the infinitesimal ones.

There is evidence that Newton and Einstein’s theories of gravity cannot explain the dynamics of a universe made up solely of baryons and radiation. To be able to understand the properties of galaxies, clusters of galaxies and the universe on the whole it has become commonplace to invoke the presence of dark matter. An alternative approach is to modify the gravitational field equations to accommodate observations. We propose a new class of gravitational theories in which we add a new degree of freedom, the Aether, in the form of a vector field that is coupled covariantly, but nonminimally, with the space-time metric. We explore the Newtonian and non-Newtonian limits, discuss the conditions for these theories to be consistent and explore their effect on cosmology.