We study the cosmic microwave background (CMB) anisotropy due to spherically symmetric nonlinear structures in flat universes with dust and a cosmological constant. By modeling a time-evolving spherical compensated void/lump by Lemaitre-Tolman-Bondi spacetimes, we numerically solve the null geodesic equations with the Einstein equations. We find that a nonlinear void redshifts the CMB photons that pass through it regardless of the distance to it. In contrast, a nonlinear lump blueshifts (or redshifts) the CMB photons if it is located near (or sufficiently far from) us. The present analysis comprehensively covers previous works based on a thin-shell approximation and a linear/second-order perturbation method and the effects of shell thickness and full nonlinearity. Our results indicate that, if quasilinear and large ($\gtrsim 100\mathrm{Mpc}$) voids/lumps would exist, they could be observed as cold or hot spots with temperature variance $\gtrsim {10}^{-5}\mathrm{K}$ in the CMB sky.

In this work we show that the presence of a vector field on cosmological scales could explain the present phase of accelerated expansion of the Universe. The proposed theory contains no dimensional parameters nor potential terms and does not require unnatural initial conditions in the early universe, thus avoiding the so-called cosmic coincidence problem. In addition, it fits the data from high-redshift supernovae with excellent precision, making definite predictions for cosmological parameters. Upcoming observations will be able to clearly discriminate this model from standard cosmology with cosmological constant.

The Kroll-Lee-Zumino renormalizable Abelian quantum field theory of pions and a massive $\rho$-meson is used to calculate the scalar radius of the pion at next-to-leading (one-loop) order in perturbation theory. Because of renormalizability, this determination involves no free parameters. The result is $⟨r_{\pi }^2{⟩}_s=0.40{\mathrm{fm}}^2$. This value gives for ${\overline{\ell }}_4$, the low energy constant of chiral perturbation theory, ${\overline{\ell }}_4=3.4$, and $F_{\pi }/F=1.05$, where $F$ is the pion decay constant in the chiral limit. Given the level of accuracy in the masses and the $\rho \pi \pi$ coupling, the only sizable uncertainty in this result is due to the (uncalculated) next-to-next-to-leading order contribution.

In this work the flavor-changing, rare $t\to cgg$ decay induced by mediation of scalar and tensor unparticles is studied. Using the standard model result for the branching ratio of the $t\to cgg$ decay, the parameter space of $d_{\mathcal{U}}$ and ${\Lambda }_{\mathcal{U}}$, where the branching ratio of this decay exceeds the one predicted by the standard model, is obtained. Measurement of the branching ratio larger than ${10}^{-9}$ can give valuable information for establishing unparticle physics.

We calculate numerically the density of states $n(S)$ for $SU(2)$ lattice gauge theory on $L^4$ lattices [$S$ is the Wilson’s action and $n(S)$ measures the relative number of ways $S$ can be obtained]. Small volume dependences are resolved for small values of $S$. We compare $\ln (n(S))$ with weak and strong coupling expansions. Intermediate order expansions show a good overlap for values of $S$ corresponding to the crossover. We relate the convergence of these expansions to those of the average plaquette. We show that, when known logarithmic singularities are subtracted from $\ln (n(S))$, expansions in Legendre polynomials appear to converge and could be suitable to determine the Fisher’s zeros of the partition function.

We study the transverse and longitudinal momentum spectra of fermions produced in a strong, time-dependent non-Abelian SU(2) field. Different time-dependent field strengths are introduced. The momentum spectra are calculated for the produced fermion pairs in a kinetic model. The obtained spectra are similar to the Abelian case, and they display exponential or polynomial behavior at high $p_T$, depending on the given time dependence. We investigated different color initial conditions and discuss the recognized scaling properties for both Abelian and SU(2) cases.

We obtain new five-dimensional supersymmetric rotating multi-Kaluza-Klein black hole solutions with the Gödel parameter in the Einstein-Maxwell system with a Chern-Simons term. These solutions have no closed timelike curve outside the black hole horizons. At infinity, the space-time is effectively four-dimensional. Each horizon admits various lens space topologies $L(n;1)={\mathrm{S}}^3/{\mathbb{Z}}_n$ in addition to a round ${\mathrm{S}}^3$. The space-time can have outer ergoregions disjointed from the black hole horizons, as well as inner ergoregions attached to each horizon. We discuss the rich structures of ergoregions.

Observational limits on the high-energy neutrino background have been used to place general constraints on dark matter that annihilates only into standard model particles. Dark matter particles that annihilate into neutrinos will also inevitably branch into electromagnetic final states through higher-order tree and loop diagrams that give rise to charged leptons, and these charged particles can transfer their energy into photons via synchrotron radiation or inverse Compton scattering. In the context of effective field theory, we calculate the loop-induced branching ratio to charged leptons and show that it is generally quite large, typically $\gtrsim 1\%$, when the scale of the dark matter mass exceeds the electroweak scale, $M_W$. For a branching fraction $\gtrsim 3\%$, the synchrotron radiation bounds on dark matter annihilation are currently stronger than the corresponding neutrino bounds in the interesting mass range from 100 GeV to 1 TeV. For dark matter masses below $M_W$, our work provides a plausible framework for the construction of a model for “neutrinos-only” dark matter annihilations.

We present a proposal for the full phase-space distribution of the Milky Way halo. The model is axially and reflection symmetric and its time evolution is self-similar. It describes the halo as a set of discrete dark matter flows with stated densities and velocity vectors everywhere. We first discuss the general conditions under which the time evolution of a cold collisionless self-gravitating fluid is self-similar, and show that symmetry is not necessary for self-similarity. When spherical symmetry is imposed, the model is the same as described by Fillmore and Goldreich, and by Bertschinger, twenty-three years ago. The spherically symmetric model depends on one dimensionless parameter $ϵ$ and two dimensionful parameters. We set $ϵ=0.3$, a value consistent with the slope of the power spectrum of density perturbations on galactic scales. The dimensionful parameters are determined by the galactic rotation velocity ($220\mathrm{km}/\mathrm{s}$) at the position of the Sun and by the age of the Galaxy (13.7 Gyr). The properties of the outer caustics are derived in the spherically symmetric model. The structure of the inner halo depends on the angular momentum distribution of the dark matter particles. We assume that distribution to be axial and reflection symmetric, and dominated by net overall rotation. The inner caustics are rings whose radii are determined in terms of a single additional parameter $j_{\max }$. We summarize the observational evidence in support of the model. The evidence is consistent with $j_{\max }=0.18$ in Concordance cosmology, equivalent to $j_{\max ,\mathrm{old}}=0.26$ in Einstein-de Sitter cosmology. We give formulas to estimate the flow densities and velocity vectors anywhere in the Milky Way halo. The properties of the first 40 flows at the location of the Earth are listed.

We calculate the shear viscosity $\eta \approx {\eta }_{\mathrm{e}\mu }+{\eta }_{\mathrm{n}}$ in a neutron star core composed of nucleons, electrons, and muons (${\eta }_{\mathrm{e}\mu }$ being the electron-muon viscosity, mediated by collisions of electrons and muons with charged particles, and ${\eta }_{\mathrm{n}}$ the neutron viscosity, mediated by neutron-neutron and neutron-proton collisions). Deriving ${\eta }_{\mathrm{e}\mu }$, we take into account the Landau damping in collisions of electrons and muons with charged particles via the exchange of transverse plasmons. It lowers ${\eta }_{\mathrm{e}\mu }$ and leads to the nonstandard temperature behavior ${\eta }_{\mathrm{e}\mu }\propto T^{-5/3}$. The viscosity ${\eta }_{\mathrm{n}}$ is calculated taking into account that in-medium effects modify nucleon effective masses in dense matter. Both viscosities, ${\eta }_{\mathrm{e}\mu }$ and ${\eta }_{\mathrm{n}}$, can be important, and both are calculated including the effects of proton superfluidity. They are presented in the form valid for any equation of state of nucleon dense matter. We analyze the density and temperature dependence of $\eta$ for different equations of state in neutron star cores, and compare $\eta$ with the bulk viscosity in the core and with the shear viscosity in the crust.

The rare $B_c\to D_s{\ell }^{+}{\ell }^{-}$ decay is investigated by using the most general model-independent effective Hamiltonian. The general expressions of longitudinal, normal, and transversal polarization asymmetries for ${\ell }^{-}$ and ${\ell }^{+}$ and the combined asymmetries of them are found. The dependencies of the branching ratios and polarizations on the new Wilson coefficients are presented. The analysis shows that the branching ratios and the lepton polarization asymmetries are very sensitive to the scalar- and tensor-type interactions. These results will be very useful in searching new physics beyond the standard model.

It has been controversial whether ${\eta }_b$ can be discovered in Tevatron Run 2 through the decay ${\eta }_b\to J/\psi J/\psi$ followed by $J/\psi \to {\mu }^{+}{\mu }^{-}$. I clear this controversy by an explicit calculation which predicts $\mathrm{Br}[{\eta }_b\to J/\psi J/\psi ]$ to be of order ${10}^{-8}$. It is concluded that observing ${\eta }_b$ through this decay mode in Tevatron Run 2 may be rather unrealistic. The ${\eta }_b$ may be observed in the forthcoming CERN LHC experiments through the 4-lepton channel, if the background events can be significantly reduced by imposing some kinematical cuts. By some rough but plausible considerations, I find that the analogous decay processes ${\eta }_b\to VV$, $D^{*}{\overline{D}}^{*}$ also have very suppressed branching ratios; nevertheless it may be worth looking for ${\eta }_b$ at LHC and Super B factory through the decay modes ${\eta }_b\to K_S{K}^{\pm }{\pi }^{\mp }$, $D^{*}\overline{D}$.

We explore an alternative strategy to determine the neutrino mass hierarchy by making use of possible future neutrino facilities at Fermilab. Here, we use $CPT$-conjugate neutrino channels, exploiting a ${\nu }_{\mu }$ beam from the NuMI beamline and a ${\overline{\nu }}_e$ beam from a beta-beam experimental setup. Both experiments are performed at approximately the same $⟨E⟩/L$. We present different possible accelerator scenarios for the beta-beam neutrino setup and fluxes. This $CPT$-conjugate neutrino channel scenario can extract the neutrino mass hierarchy down to ${sin}^{2}2{\theta }_{13}\approx 0.02$.

In this paper, we present an exact spherically symmetric solution of third order Lovelock gravity in $n$ dimensions which describes the gravitational collapse of a null dust fluid. This solution is asymptotically (anti-)de Sitter or flat depending on the choice of the cosmological constant. Using the asymptotically flat solution for $n\ge 7$ with a power-law form of the mass as a function of the null coordinate, we present a model for a gravitational collapse in which a null dust fluid radially injects into an initially flat and empty region. It is found that a naked singularity is inevitably formed whose strength is different for the $n=7$ and $n\ge 8$ cases. In the $n=7$ case, the limiting focusing condition for the strength of curvature singularity is satisfied. But for $n\ge 8$, the strength of curvature singularity depends on the rate of increase of mass of the spacetime. These considerations show that the third order Lovelock term weakens the strength of the curvature singularity.

Canonical vacuum gravity is expressed in generally covariant form in order that spacetime diffeomorphisms be represented within its equal-time phase space. In accordance with the principle of general covariance and ideas developed within history phase-space formalisms in [I. Kouletsis and K. V. Kuchař, Phys. Rev. D 65, 125026 (2002)], [K. Savvidou, Classical Quantum Gravity 18, 3611 (2001)], [K. Savvidou, Classical Quantum Gravity 21, 615 (2004)], [K. Savvidou, Classical Quantum Gravity 21, 631 (2004)], the time mapping $\mathbf{T}$: $\mathcal{M}\to \mathbb{R}$ and the space mapping $\mathbf{X}$: $\mathcal{M}\to \Sigma$ that define the Dirac–Arnowitt-Deser-Misner (ADM) foliation are incorporated into the framework of the Hilbert variational principle. The resulting canonical action encompasses all individual Dirac-ADM actions, corresponding to different choices of foliating vacuum spacetimes by spacelike hypersurfaces. The equal-time phase space $\mathcal{P}=\{g_{ij},p^{ij},Y^{\alpha },P_{\alpha }\}$ includes the embeddings $Y^{\alpha }$: $\Sigma \to \mathcal{M}$ and their conjugate momenta $P_{\alpha }$. It is constrained by eight first-class constraints. The constraint surface $\mathcal{C}$ is determined by the super-Hamiltonian and supermomentum constraints of vacuum gravity and the vanishing of the embedding momenta. Deformations of the time and space mappings, $\delta \mathbf{T}$ and $\delta \mathbf{X}$, and spacetime diffeomorphisms, $V\in \mathrm{LDiff}\mathcal{M}$, induce symplectic diffeomorphisms of $\mathcal{P}$. While the generator ${\mathcal{D}}_{(\delta \mathbf{T},\delta \mathbf{X})}$ of deformations depends on all eight constraints, the generator ${\mathcal{D}}_V$ of spacetime diffeomorphisms depends only on the embedding momentum constraints. As a result, spacetime observables, namely, dynamical variables $F$ on $\mathcal{P}$ that are invariant under spacetime diffeomorphisms, $\{F,{\mathcal{D}}_V\}{\mid }_{\mathcal{C}}=0$, are not necessarily invariant under the deformations of the mappings, $\{F,{\mathcal{D}}_{(\delta \mathbf{T},\delta \mathbf{X})}\}{\mid }_{\mathcal{C}}\ne 0$, nor are they constants of the motion, $\{F,\int d^{3}x\mathcal{H}\}{\mid }_{\mathcal{C}}\ne 0$. Dirac observables form only a subset of spacetime observables that are invariant under the transformations of $\mathbf{T}$ and $\mathbf{X}$ and do not evolve in time. In this generally covariant framework, the conventional interpretation of the canonical theory, due to Bergmann and Dirac, amounts to postulating that the transformations of the reference system $(\mathbf{T},\mathbf{X})$ have no measurable consequences; i.e., that all first-class constraints generate gauge transformations. If this postulate is not deemed necessary, canonical gravity admits no classical problem of time.

We quantitatively address whether IceCube, a kilometer-scale neutrino detector under construction at the South Pole, can observe neutrinos pointing back at the accelerators of the Galactic cosmic rays. The photon flux from candidate sources identified by the Milagro detector in a survey of the TeV sky is consistent with the flux expected from a typical cosmic-ray generating supernova remnant interacting with the interstellar medium. We show here that IceCube can provide incontrovertible evidence of cosmic-ray acceleration in these sources by detecting neutrinos. We find that the signal is optimally identified by specializing to events with energies above 30 TeV where the atmospheric neutrino background is low. We conclude that evidence for a correlation between the Milagro and IceCube sky maps should be conclusive after several years.

In the covariant light-front quark model, we investigate the form factors of $D_s\to K$, $K^{*}$, $\varphi$ transitions and compare our results with the experimental data and the previous theoretical studies. The semileptonic $D_s$ decays are studied: our result for the branching ratio of $D_s\to \varphi l^{+}\nu$ is consistent with the data; while the other predictions, such as $\mathcal{B}\mathcal{R}(D_s^{+}\to {\overline{K}}^0{l}^{+}\nu )$, the branching ratio and the polarization of $D_s\to {\overline{K}}^{*0}{l}^{+}\nu$, will be tested at the future experiments. Utilizing the results for form factors, we then calculate the two-body nonleptonic $D_s$ decays and find: up to the leading power accuracy, theoretical predictions on branching ratios of nonleptonic $D_s$ decays are typically smaller than the experimental data by a factor of 1.5–2.0. Large contributions from weak annihilation diagrams, together with the $s$, $t$-channel final state interactions, are expected to resolve this problem. The $D_s\to K^{+}{K}^{*0}$ decay, which can be easily measured in the $K^{+}{K}^{+}{\pi }^{-}$ final state, can directly shed light on internal information of the doubly Cabibbo-suppressed decay amplitudes.

We argue that one can see a specific class of “stringy” D-instantons in the underlying 4D gauge theory as the UV completion of an ordinary gauge instanton of a completely broken gauge group corresponding to the “empty” cycle on which the D-instanton is located. In this sense, the D-instanton-induced nonperturbative superpotential can be qualitatively inferred directly from pure field-theory considerations.

The static three-quark potential and pseudopotential of a pure $SU(3)$ gauge theory are studied in a five-dimensional framework known as AdS/QCD. The results support the Y-ansatz for the baryonic area law. A comparison with the quark-antiquark calculations shows the universality of the string tension as well as the spatial string tension. We also discuss extensions to $SU(N)$ gauge theories.

We construct perturbative static solutions to the classical field equations of noncommutative $U(1)$ gauge theory for the three cases: (a) space-time noncommutativity, (b) space-space noncommutativity, and (c) both (a) and (b). The solutions tend to the Coulomb solution at spatial infinity and are valid for intermediate values of the radial coordinate $r$. They yield a self-charge inside a sphere of radius $r$ centered about the origin which increases with decreasing $r$ for case (a), and decreases with decreasing $r$ for case (b). For case (a) this may mean that the exact solution screens an infinite charge at the origin, while for case (b) it is plausible that the charge density is well behaved at the origin, as happens in Born-Infeld electrodynamics. For both cases (a) and (b) the self-energy in the intermediate region grows faster as $r$ tends to the origin than that of the Coulomb solution. It then appears that the divergence of the classical self-energy is more severe in the noncommutative theory than it is in the corresponding commutative theory. We compute the lowest order effects of these solutions on the hydrogen atom spectrum and use them to put experimental bounds on the space-time and space-space noncommutative scales. For the former we get a significant improvement over previous bounds. We find that cases (a) and (b) have different experimental signatures.