Neutral stellar core at or over nuclear densities is described by a positive charged baryon core and negative charged electron fluid since they possess different masses and interactions. Based on a simplified model of a gravitationally collapsing or pulsating baryon core, we approximately integrate the Einstein-Maxwell equations and the equations for the number and energy-momentum conservation of complete degenerate electron fluid. We show possible electric processes that lead to the production of electron-positron pairs in the boundary of a baryon core and calculate the number and energy of electron-positron pairs. This can be relevant for understanding the energetic sources of supernovae and gamma-ray bursts.

A new method for solving the relativistic inverse stellar structure problem is presented. This method determines a spectral representation of the unknown high-density portion of the stellar equation of state from a knowledge of the total masses $M$ and radii $R$ of the stars. Spectral representations of the equation of state are very efficient, generally requiring only a few spectral parameters to achieve good accuracy. This new method is able, therefore, to determine the high-density equation of state quite accurately from only a few accurately measured $[M,R]$ data points. This method is tested here by determining the equations of state from mock $[M,R]$ data computed from tabulated realistic neutron-star equations of state. The spectral equations of state obtained from these mock data are shown to agree, on average, with the originals to within a few percent (over the entire high-density range of the neutron-star interior) using only two $[M,R]$ data points. Higher accuracies are achieved when more data are used. The accuracies of the equations of state determined in these examples are shown to be nearly optimal, in the sense that their errors are comparable to the errors of the best-fit spectral representations of these realistic equations of state.

Whereas current cosmological observations suggest that the Universe is dominated by a positive cosmological constant ($\Lambda >0$), the AdS/CFT correspondence tells us that the case $\Lambda <0$ is still worthy of consideration. In this paper we study the McVittie solution with $\Lambda <0$. Following a related study, the solution is understood here by way of a systematic construction of conformal diagrams based on detailed numerical integrations of the null geodesic equations. As in the pure Robertson-Walker case, we find that $\Lambda <0$ ensures collapse to a Big Crunch, a feature which completely dominates the global structure.

This short paper is devoted to the Hamiltonian formulation of the conformal decomposition of the gravitational field that was performed in [gr-qc/0501092]. We also analyze the gauge fixed form of the theory when we fix the conformal symmetry by imposing the condition $\sqrt{g}=1$.

We explore three different methods based on weak lensing to extract cosmological constraints from the large-scale structure. In the first approach [method I: U. Seljak et al., Phys. Rev. D 71, 103515 (2005)], small-scale galaxy or cluster lensing measurements of their halo mass provide a constraint on the halo bias, which can be combined with the large-scale galaxy or cluster clustering to measure the dark matter clustering. In the second approach [method II: T. Baldauf et al., Phys. Rev. D 81, 063531 (2010)], large-scale galaxy clustering and large-scale galaxy-galaxy lensing each trace the large-scale dark matter clustering, and the two can be combined into a direct measurement of the dark matter clustering. These two methods can be combined into one method $\mathrm{I}+\mathrm{II}$ to make use of lensing measurements on all scales. In the third approach (method III), we add abundance information to the method I, which is a version of self-calibrated cluster abundance method. We explore the statistical power of these three approaches as a function of galaxy or cluster luminosity to investigate the optimal mass range for each method and their cosmological constraining power. In the case of the Sloan Digital Sky Survey, we find that the three methods give comparable constraints, but not in the same mass range: the method II works best for halos of $M\sim {10}^{13}{M}_{\odot }$, typical of luminous red galaxies, and the methods I and III work best for halos of $M\sim {10}^{14}{M}_{\odot }$, typical of low-mass clusters. We discuss the robustness of each method against various systematics. Furthermore, we extend the analysis to the future large-scale galaxy surveys and find that the cluster abundance method is not superior to the combined method $\mathrm{I}+\mathrm{II}$, both in terms of statistical power and robustness against systematic errors. The cosmic shear-shear correlation analysis in the future surveys yields constraints as strong as the combined method, but suffer from additional systematic effects. We thus advocate the combined analysis of clustering and lensing (method $\mathrm{I}+\mathrm{II}$) as a powerful alternative to other large-scale probes. Our analysis provides a guidance to observers planning large-scale galaxy surveys such as the DES, Euclid, and the LSST.

We study multifield Dirac-Born-Infeld (DBI) inflation models with a waterfall phase transition. This transition happens for a D3 brane moving in the warped conifold if there is an instability along angular directions. The transition converts the angular perturbations into the curvature perturbation. Thanks to this conversion, multifield models can evade the stringent constraints that strongly disfavor single field ultraviolet (UV) DBI inflation models in string theory. We explicitly demonstrate that our model satisfies current observational constraints on the spectral index and equilateral non-Gaussianity as well as the bound on the tensor to scalar ratio imposed in string theory models. In addition, we show that large local type non-Gaussianity is generated together with equilateral non-Gaussianity in this model.

We study the dynamical stability of tachyacoustic cosmological models, in which primordial perturbations are generated by a shrinking sound horizon during a period of decelerating expansion. Such models represent a potential alternative to inflationary cosmology, but the phase-space behavior of tachyacoustic solutions has not previously been investigated. We numerically evaluate the dynamics of two noncanonical Lagrangians, a cuscuton-like Lagrangian and a Dirac-Born-Infeld Lagrangian, which generate a scale-invariant spectrum of perturbations. We show that the power-law background solutions in both cases are dynamical attractors.

Fluids often display dissipative properties. We explore dissipation in the form of bulk viscosity in the cold dark matter fluid. We constrain this model using current data from supernovae, baryon acoustic oscillations and the cosmic microwave background. Considering the isotropic and homogeneous background only, viscous dark matter is allowed to have a bulk viscosity $\lesssim {10}^7\mathrm{Pa}·\mathrm{s}$, also consistent with the expected integrated Sachs-Wolfe effect (which plagues some models with bulk viscosity). We further investigate the small-scale formation of viscous dark matter halos, which turns out to place significantly stronger constraints on dark matter viscosity. The existence of dwarf galaxies is guaranteed only for much smaller values of dark matter viscosity, $\lesssim {10}^{-3}\mathrm{Pa}·\mathrm{s}$.

Direct observations of the Hubble rate, from cosmic chronometers and the radial baryon acoustic oscillation scale, can outperform supernovae observations in understanding the expansion history, because supernovae observations need to be differentiated to extract $H(z)$. We use existing $H(z)$ data and smooth the data using a new Gaussian processes package, GaPP, from which we can also estimate derivatives. The obtained Hubble rate and its derivatives are used to reconstruct the equation of state of dark energy and to perform consistency tests of the $\Lambda \mathrm{CDM}$ model, some of which are newly devised here. Current data are consistent with the concordance model, but are rather sparse. Future observations will provide a dramatic improvement in our ability to constrain or refute the concordance model of cosmology. We produce simulated data to illustrate how effective $H(z)$ data will be in combination with Gaussian processes.

The observations of gravitational-wave signals from astrophysical sources such as binary inspirals will be used to test general relativity for self-consistency and against alternative theories of gravity. I describe a simple formula that can be used to characterize the prospects of such tests, by estimating the matched-filtering signal-to-noise ratio required to detect non-general-relativistic corrections of a given magnitude. The formula is valid for sufficiently strong signals; it requires the computation of a single number, the fitting factor between the general-relativistic and corrected waveform families; and it can be applied to all tests that embed general relativity in a larger theory, including tests of individual theories such as Brans-Dicke gravity, as well as the phenomenological schemes that introduce corrections and extra terms in the post-Newtonian phasing expressions of inspiral waveforms. The formula suggests that the volume-limited gravitational-wave searches performed with second-generation ground-based detectors would detect alternative-gravity corrections to general-relativistic waveforms no smaller than 1%–10% (corresponding to fitting factors of 0.9 to 0.99).

We consider the transitions from the $Z_b(10610)$ and $Z_b(10650)$ resonances to the states of bottomonium with emission of a pion. The $Z_b$ resonances are viewed as “molecular” objects of a large spatial size made of heavy $B^{(*)}$ mesons, while the states of bottomonium are considered to be compact, so that an application of the leading (dipole) term in the QCD multipole expansion is assumed to be justified. In this way we calculate the ratios of the decay rates to the final states ${\rm Y}(nS)\pi$ with $n=1$, 2, 3, and the ratio of the decay rates to $h_b(kP)\pi$ with $k=1$ and 2. We find our estimates in reasonable agreement with recent experimental data.

We calculate the radiative corrections to the Dalitz plot of $K_{l3}^{\pm }$ decays to order $(\alpha /\pi )(q/M_1)$, where $q$ is the momentum transfer and $M_1$ is the mass of the kaon. We restrict the analysis to the so-called four-body region, which arises when no discrimination of real photons is made either kinematically or experimentally. We present our results in two ways: the first one with the triple integration over the photon kinematical variables ready to be performed numerically and the second one in a fully analytical form. Our results can be useful in experimental analyses of the Dalitz plot, by evaluating the model-independent coefficients of the quadratic products of the form factors; we provide some numbers as a case example. We find a small, albeit non-negligible, contribution from the four-body region to the radiative correction to the total decay rate of $K_{l3}^{\pm }$ decays.

Motivated by the problem of thermalization in heavy ion collisions, we present numerical simulations of the nonequilibrium evolution of the $O(N)$ model in $1+2$ dimensions with longitudinal expansion and in the presence of a background field. We work in the next-to-leading-order approximation of the $1/N$ expansion and consider both the strong and weak coupling cases. Special emphasis is put on the difference between the two-particle irreducible formalism and the classical statistical approach. In the two-particle irreducible case at strong coupling, we find some evidence of the Bose-Einstein (exponential) distribution in the expanding system.

We study the energy-momentum tensor of stable, metastable and unstable $Q$-balls in scalar field theories with U(1) symmetry. We calculate properties such as charge, mass, mean square radii and the constant $d_1$ (“$D$-term”) as functions of the phase space angular velocity $\omega$. We discuss the limits when $\omega$ approaches the boundaries of the region in which solutions exist, and derive analytical results for the quantities in these limits. The central result of this work is the rigorous proof that $d_1$ is strictly negative for all finite energy solutions in the $Q$-ball system.

We consider the neutral triple-gauge boson production process in the context of large extra dimensions (LED) models including the Kaluza-Klein (KK) excited gravitons at future linear colliders, say ILC(CLIC). We consider $\gamma \gamma \gamma$, $\gamma \gamma Z$, $\gamma ZZ$, and $ZZZ$ production processes, and analyze their impacts on both the total cross section and some key distributions. These processes are important for new physics searches at linear colliders. Our results show that KK graviton exchange has the most significant effect on $e^{-}{e}^{+}\to \gamma ZZ$ among the four processes with relatively small $M_S$, while it has the largest effect on $e^{-}{e}^{+}\to \gamma \gamma \gamma$ with larger $M_S$. By using the neutral triple-gauge boson production we could set the discovery limit on the fundamental Plank scale $M_S$ up to around 6–9 TeV for $\delta =4$ at the 3 TeV CLIC.

The results of a multilepton search conducted by the CMS collaboration with $5{\mathrm{fb}}^{-1}$ of data collected from 7 TeV $pp$ collisions are used to place the first bound on the rare flavor-changing decay of the top quark to a Higgs boson and charm quark. Combining results from a number of exclusive three- and four-lepton search channels yields an estimated upper limit of $\mathrm{Br}(t\to ch)<2.7\%$ for a Higgs boson mass of 125 GeV. The sensitivity of future dedicated searches for $t\to ch$ could be improved by adding exclusive same sign dilepton channels, as well as by subdividing channels based on $b$-quark tagging and partial kinematic top quark and Higgs boson tagging. This bound may be interpreted more widely within a range of new physics processes that yield final states with a $W$-boson in association with a Higgs boson. For such processes with kinematics that are similar to top-anti-top production and decay, the estimated limit on cross section times branching ratio corresponds to roughly $\sigma ·\mathrm{Br}(pp\to WhX)<9\mathrm{pb}$.

Supersymmetric models with bilinear $R$-parity violation can account for the observed neutrino masses and mixing parameters indicated by neutrino oscillation data. We consider minimal supergravity versions of bilinear $R$-parity violation where the lightest supersymmetric particle is a neutralino. This is unstable, with a large enough decay length to be detected at the CERN Large Hadron Collider. We analyze the Large Hadron Collider potential to determine the lightest supersymmetric particle properties, such as mass, lifetime and branching ratios, and discuss their relation to neutrino properties.

We report on our calculation of the nucleon axial charge $g_{\mathrm{A}}$ in QCD with two flavors of dynamical quarks. A detailed investigation of systematic errors is performed, with a particular focus on contributions from excited states to three-point correlation functions. The use of summed operator insertions allows for a much better control over such contamination. After performing a chiral extrapolation to the physical pion mass, we find $g_{\mathrm{A}}=1.223\pm 0.063(\mathrm{stat}{)}_{-0.060}^{+0.035}(\mathrm{syst})$, in good agreement with the experimental value.

The free energy of effective spin or “Polyakov line” models with a chemical potential, based on the $\mathrm{U}(N)$ group, does not depend on the chemical potential. In a mean field-inspired expansion, we show how the condition of unit determinant, taking $\mathrm{U}(N)$ to $\mathrm{SU}(N)$, reintroduces the chemical potential, and allows us to express the free energy, as a function of mean field variational parameters, in terms of an expansion in the baryon (rather than the quark) fugacity at each lattice site. We solve the SU(3) mean field equations numerically to determine the phase diagram and compute observables. We also calculate the first corrections to the leading order mean field results, and find that these can significantly shift the endpoint of a line of first order transitions. The problem of deriving an effective spin model from full QCD is discussed.

We investigate the parton-distribution functions (PDFs) for the positively charged pion and kaon at a low renormalization scale $\sim 1\mathrm{GeV}$. To this end, we employ the gauge-invariant effective chiral action from the nonlocal chiral-quark model, resulting in the vector currents being conserved. All the model parameters are determined phenomenologically with the normalization condition for PDF and the empirical values for the pseudoscalar meson weak-decay constants. We consider the momentum dependence of the effective quark mass properly within the model calculations. It turns out that the leading local contribution provides about 70% of the total strength for PDF, whereas the nonlocal one, which is newly taken into account in this work for the gauge invariance, does the rest. High-$Q^2$ evolution to $27{\mathrm{GeV}}^2$ is performed for the valance-quark distribution function, using the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi equation. The moments for the pion and kaon valance-quark distribution functions are also computed. The numerical results are compared with the empirical data and theoretical estimations, and show qualitatively agreement with them.