In a logamediate inflationary universe model we introduce the curvaton field in order to bring this inflationary model to an end. In this approach we determine the reheating temperature. We also outline some interesting constraints on the parameters that describe our models. Thus, we give the parameter space in this scenario.

We discuss recent observations of high energy cosmic ray positrons and electrons in the context of hadronic interactions in supernova remnants (SNRs), the suspected accelerators of galactic cosmic rays. Diffusive shock acceleration can harden the energy spectrum of secondary positrons relative to that of the primary protons and electrons and thus explain the rise in the positron fraction observed by PAMELA above 10 GeV. We normalize the hadronic interaction rate by holding pion decay to be responsible for the gamma rays detected by HESS from some SNRs. By simulating the spatial and temporal distribution of SNRs in the Galaxy according to their known statistics, we are able to then fit the electron (plus positron) energy spectrum measured by Fermi. It appears that IceCube has good prospects for detecting the hadronic neutrino fluxes expected from nearby SNRs.

We report on measurements of the cosmic-ray induced $\gamma$-ray emission of Earth’s atmosphere by the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. The Large Area Telescope has observed the Earth during its commissioning phase and with a dedicated Earth limb following observation in September 2008. These measurements yielded $\sim 6.4\times {10}^6$ photons with energies $>100\mathrm{MeV}$ and $\sim 250$ hours total live time for the highest quality data selection. This allows the study of the spatial and spectral distributions of these photons with unprecedented detail. The spectrum of the emission—often referred to as Earth albedo gamma-ray emission—has a power-law shape up to 500 GeV with spectral index $\Gamma =2.79\pm 0.06$.

We use a variant of principal component analysis to investigate the possible temporal evolution of the dark energy equation of state, $w(z)$. We constrain $w(z)$ in multiple redshift bins, utilizing the most recent data from type Ia supernovae, the cosmic microwave background, baryon acoustic oscillations, the integrated Sachs-Wolfe effect, galaxy clustering, and weak lensing data. Unlike other recent analyses, we find no significant evidence for evolving dark energy; the data remain completely consistent with a cosmological constant. We also study the extent to which the time evolution of the equation of state would be constrained by a combination of current- and future-generation surveys, such as Planck and the Joint Dark Energy Mission.

We investigate the prospects to extract supersymmetric couplings from a decay length measurement at the LHC. Specifically, we exploit the opportunity of a light and long-lived stop which is pair-produced through gluinos in association with like-sign top quarks. Any observed finite value of the stop decay length strongly supports models in which flavor is broken in a minimal way solely by the standard model Yukawa couplings. We find that a 1 picosecond stop lifetime, dominated by $\tilde{t}\to c{\chi }^0$ decays, yields macroscopic transverse impact parameters of about 180 microns. If the lightest neutralino is predominantly Higgsino or very close in mass to the light stop, the stop lifetime even increases and allows to observe stop tracks and possibly secondary vertices directly. Measuring squark flavor violation with the stop decay length works also with a gravitino lightest supersymmetric particle if the neutralino is the next lightest supersymmetric particle. For this case, opportunities from $\tilde{t}\to c{\chi }^0\to c\gamma \tilde{G}$ decays for very light gravitinos with mass $\lesssim \mathrm{keV}$ are pointed out.

We study the decays of a standard model-like minimal supersymmetric standard model Higgs boson to pairs of neutralinos, each of which subsequently decays promptly to a photon and a gravitino. Such decays can arise in supersymmetric scenarios where supersymmetry breaking is mediated to us by gauge interactions with a relatively light gauge messenger sector ($M_{\mathrm{mess}}\lesssim 100\mathrm{TeV}$). This process gives rise to a collider signal consisting of a pair of photons and missing energy. In the present work we investigate the bounds on this scenario within the minimal supersymmetric standard model from existing collider data. We also study the prospects for discovering the Higgs boson through this decay mode with upcoming data from the Tevatron and the LHC.

Top quark plus jets production at a hadron collider allows us to study the couplings of the top quark. In the standard model, two single top processes contribute to the top-jets final state. Beyond the standard model, additional direct top production can occur. All three processes probe top gauge couplings including flavor mixing. The structure of accompanying QCD jets allows us to separate the direct top signal from the QCD backgrounds as well as to disentangle the three top plus jets production mechanisms orthogonally to the usual bottom tags.

Branching fractions and $CP$-violating asymmetries of charmless ${\overline{B}}_s\to PP$, $VP$, $VV$ decays ($P$ and $V$ denoting pseudoscalar and vector mesons, respectively) are reexamined in the framework of QCD factorization (QCDF). We take into account subleading power corrections to the penguin annihilation topology and to color-suppressed tree amplitudes that are crucial for resolving the $CP$ puzzles and rate deficit problems with penguin-dominated two-body decays and color-suppressed tree-dominated ${\pi }^0{\pi }^0$ and ${\rho }^0{\pi }^0$ modes in the $B_{u,d}$ sector. Many of the $B_s\to h_1{h}_2$ decays can be related to $B_d\to h_1{h}_2$ ones via $U$-spin or SU(3) symmetry. Some useful model-independent relations can be derived and tested. Mixing-induced $CP$ asymmetries for many of the penguin-dominated decays are predicted to be very small in the standard model. They are sensitive to new physics and offer rich possibilities of new discoveries. Measurements of direct $CP$-violating asymmetries can be used to discriminate QCDF from other competing approaches such as pQCD and soft-collinear effective theory.

We investigate the chiral magnetic effect (CME) under a strong magnetic field $\mathit{B}=B_0{\widehat{x}}_3$ at low temperature $T\lesssim T_c^{\chi }$. For this purpose, we employ the instanton vacuum configuration with the finite instanton-number fluctuation $\Delta$, which relates to the nontrivial topological charge $Q_t$. We compute the vacuum expectation values of the local chiral density $⟨{\rho }_{\chi }⟩$, chiral charge density $⟨n_{\chi }⟩$, and induced electromagnetic current $⟨j_{\mu }⟩$, which signal the CME, as functions of $T$ and $B_0$. We observed that the longitudinal electromagnetic current is much larger than the transverse one, $|j_{\perp }/j_{\parallel }|\sim Q_t$, and $⟨n_{\chi }⟩$ is equal to $|⟨j_{3,4}⟩|$. It also turns out that the CME becomes insensitive to the magnetic field as $T$ increases, since the instanton effect decreases. Within our framework, the instanton contribution to the CME becomes almost negligible beyond $T\approx 300\mathrm{MeV}$.

It has been conjectured that higher-dimensional rotating black holes become unstable at a sufficiently large value of the rotation, and that new black holes with pinched horizons appear at the threshold of the instability. We search numerically and find the stationary axisymmetric perturbations of Myers-Perry black holes with a single spin that mark the onset of the instability and the appearance of the new black hole phases. We also find new ultraspinning Gregory-Laflamme instabilities of rotating black strings and branes.

We determine the strong coupling constant ${\alpha }_s$ and its energy dependence from the $p_T$ dependence of the inclusive jet cross section in $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$. The strong coupling constant is determined over the transverse momentum range $50<p_T<145\mathrm{GeV}$. Using perturbative QCD calculations to order $\mathcal{O}({\alpha }_s^3)$ combined with $\mathcal{O}({\alpha }_s^4)$ contributions from threshold corrections, we obtain ${\alpha }_s(M_Z)={0.1161}_{-0.0048}^{+0.0041}$. This is the most precise result obtained at a hadron-hadron collider.

We consider the Casimir energy due to a massless scalar field in a geometry of an infinite wedge closed by a Dirichlet circular cylinder, where the wedge is formed by $\delta$-function potentials, so-called semitransparent boundaries. A finite expression for the Casimir energy corresponding to the arc and the presence of both semitransparent potentials is obtained, from which the torque on the sidewalls can be derived. The most interesting part of the calculation is the nontrivial nature of the angular mode functions. Numerical results are obtained which are closely analogous to those recently found for a magnetodielectric wedge, with the same speed of light on both sides of the wedge boundaries. Alternative methods are developed for annular regions with radial semitransparent potentials, based on reduced Green’s functions for the angular dependence, which allows calculations using the multiple-scattering formalism. Numerical results corresponding to the torque on the radial plates are likewise computed, which generalize those for the wedge geometry. Generally useful formulas for calculating Casimir energies in separable geometries are derived.

The generation of a baryon asymmetry via leptogenesis is usually studied by means of classical kinetic equations whose applicability to processes in the hot and expanding early universe is questionable. The approximations implied by the state-of-the-art description can be tested in a first-principle approach based on nonequilibrium field theory techniques. Here, we apply the Schwinger-Keldysh/Kadanoff-Baym formalism to a simple toy model of leptogenesis. We find that, within the toy model, medium effects increase the vertex contribution to the $CP$-violating parameter. At high temperatures it is a few times larger than in vacuum and asymptotically reaches the vacuum value as the temperature decreases. Contrary to the results obtained earlier in the framework of thermal field theory, the corrections are only linear in the particle number densities. An important feature of the Kadanoff-Baym formalism is that it is free of the double-counting problem, i.e. no need for real intermediate state subtraction arises. In particular, this means that the structure of the equations automatically ensures that the asymmetry vanishes in equilibrium. These results give a first glimpse into a number of new and interesting effects that can be studied in the framework of nonequilibrium field theory.

A strongly well-posed initial boundary value problem based upon constraint-preserving boundary conditions of the Sommerfeld type has been established for the harmonic formulation of the vacuum Einstein’s equations. These Sommerfeld conditions have been previously presented in a four-dimensional geometric form. Here we recast the associated boundary data as three-dimensional tensor fields intrinsic to the boundary. This provides a geometric presentation of the boundary data analogous to the three-dimensional presentation of Cauchy data in terms of three-metric and extrinsic curvature. In particular, diffeomorphisms of the boundary data lead to vacuum spacetimes with isometric geometries. The proof of well-posedness is valid for the harmonic formulation and its generalizations. The Sommerfeld conditions can be directly applied to existing harmonic codes which have been used in simulating binary black holes, thus ensuring boundary stability of the underlying analytic system. The geometric form of the boundary conditions also allows them to be formally applied to any metric formulation of Einstein’s equations, although well-posedness of the boundary problem is no longer ensured. We discuss to what extent such a formal application might be implemented in a constraint-preserving manner to $3+1$ formulations, such as the Baumgarte-Shapiro-Shibata-Nakamura system which has been highly successful in binary black hole simulation.

We study past horizons in the class of type II Robinson-Trautman vacuum spacetimes with a cosmological constant. These exact radiative solutions of Einstein’s equations exist in the future of any sufficiently smooth initial data, and they approach the corresponding spherically symmetric Schwarzschild–(anti-)de Sitter metric. By analytic methods we investigate the existence, uniqueness, location, and character of the past horizons in these spacetimes. In particular, we generalize the Penrose-Tod equation for marginally trapped surfaces, which form such white-hole horizons, to the case of a nonvanishing cosmological constant, and we analyze the behavior of its solutions and visualize their evolutions. We also prove that these horizons are explicit examples of an outer trapping horizon and a dynamical horizon, so that they are spacelike past outer horizons.

Within standard quantum field theory of one scalar field we define operators conjugate to the energy-momentum operators of the theory. They are singled out by calculational simplicity in Fock space. In terms of the underlying scalar field they are nonlocal. We establish their algebra where it turns out that time and space operators do not commute. Their transformation properties with respect to the conformal group are derived. Solving their eigenvalue problem permits to reconstruct the Fock space in terms of the eigenstates. It is indicated how Paulis theorem may be circumvented. As an application we form the analogue of $S$ matrices, which yields information on the structure of the underlying space-time. Similarly, we define fields and look at their equations of motion.

We revisit the issue of the correct Lagrangian description of a perfect fluid (${\mathcal{L}}_1=P$ versus ${\mathcal{L}}_2=-\rho$) in relation with modified gravity theories in which galactic luminous matter couples nonminimally to the Ricci scalar. These Lagrangians are only equivalent when the fluid couples minimally to gravity and not otherwise; in the presence of nonminimal coupling they give rise to two distinct theories with different predictions.

By asymptotically matching a post-Newtonian (PN) metric to two perturbed Schwarzschild metrics, we generate approximate initial data (in the form of an approximate 4-metric) for a nonspinning black hole binary in a circular orbit. We carry out this matching through $O(v^4)$ in the binary’s orbital velocity $v$, and thus the resulting data, like the $O(v^4)$ PN metric, are conformally curved. The matching procedure also fixes the quadrupole and octupole tidal deformations of the holes, including the 1PN corrections to the quadrupole fields. Far from the holes, we use the appropriate PN metric that accounts for retardation, which we construct using the highest-order PN expressions available to compute the binary’s past history. The data set’s uncontrolled remainders are thus $O(v^5)$ throughout the time slice; we also generate an extension to the data set that has uncontrolled remainders of $O(v^6)$ in the purely PN portion of the time slice (i.e., not too close to the holes). This extension also includes various other readily available higher-order terms. The addition of these terms decreases the constraint violations in certain regions, even though it does not increase the data’s formal accuracy. The resulting data are smooth, since we join all the metrics together by smoothly interpolating between them. We perform this interpolation using transition functions constructed to avoid introducing excessive additional constraint violations. Because of their inclusion of tidal deformations and outgoing radiation, these data should substantially reduce both the high- and low-frequency components of the initial spurious (“junk”) radiation observed in current simulations that use conformally flat initial data. Such reductions in the nonphysical components of the initial data will be necessary for simulations to achieve the accuracy required to supply Advanced LIGO and LISA with the templates necessary for parameter estimation.

We use the solutions of the noncommutative Wheeler-DeWitt equation arising from a Kantowski-Sachs cosmological model to compute thermodynamic properties of the Schwarzschild black hole. We show that the noncommutativity in the momentum sector introduces a quadratic term in the potential function of the black hole minisuperspace model. This potential has a local minimum and thus the partition function can be computed by resorting to a saddle point evaluation in the neighborhood of the minimum. The thermodynamics of the black hole is derived and the corrections to the usual Hawking temperature and entropy exhibit a dependence on the momentum noncommutative parameter, $\eta$. Moreover, we study the $t=r=0$ singularity in the noncommutative regime and show that in this case the wave function of the system vanishes in the neighborhood of $t=r=0$.