Quantum fluctuations of a nonminimally coupled scalar field in $D$-dimensional homogeneous and isotropic background are calculated within the operator formalism in curved models with time evolutions of the scale factor that allow smooth transitions between contracting and expanding and between decelerating and accelerating regimes. The coincident propagator is derived and used to compute the one-loop backreaction from the scalar field. The inflationary infrared divergences are absent in Bunch-Davies vacuum when taking into account a preceding cosmological era or spatial curvature which can be either positive or negative. It is found that asymptotically, the backreaction energy density in the minimally coupled case grows logarithmically with the scale factor in quasi–de Sitter space and in a class of models decays in slow-roll inflation and grows as a power law during superinflation. The backreaction increases generically in a contracting phase or in the presence of a negative nonminimal coupling. The effects of the coupling and renormalization scale upon the quantum fluctuations together with the novel features due to nontrivial time evolution and spatial curvature are clarified with exact solutions and numerical examples.

We have conducted $N$-body simulations of the growth of Milky Way-sized halos in cold and warm dark matter cosmologies. The number of dark matter satellites in our simulated Milky Ways decreases with decreasing mass of the dark matter particle. Assuming that the number of dark matter satellites exceeds or equals the number of observed satellites of the Milky Way, we derive lower limits on the dark matter particle mass. We find with 95% confidence $m_s>13.3\mathrm{keV}$ for a sterile neutrino produced by the Dodelson and Widrow mechanism, $m_s>8.9\mathrm{keV}$ for the Shi and Fuller mechanism, $m_s>3.0\mathrm{keV}$ for the Higgs decay mechanism, and $m_{\mathrm{WDM}}>2.3\mathrm{keV}$ for a thermal dark matter particle. The recent discovery of many new dark matter dominated satellites of the Milky Way in the Sloan Digital Sky Survey allows us to set lower limits comparable to constraints from the complementary methods of Lyman-$\alpha$ forest modeling and x-ray observations of the unresolved cosmic x-ray background and of dark matter halos from dwarf galaxy to cluster scales. Future surveys like LSST, DES, PanSTARRS, and SkyMapper have the potential to discover many more satellites and further improve constraints on the dark matter particle mass.

Future astrophysical data sets promise to strengthen constraints on models of inflation, and extracting these constraints requires methods and tools commensurate with the quality of the data. In this paper we describe ModeCode, a new, publicly available code that computes the primordial scalar and tensor power spectra for single-field inflationary models. ModeCode solves the inflationary mode equations numerically, avoiding the slow roll approximation. It is interfaced with CAMB and CosmoMC to compute cosmic microwave background angular power spectra and perform likelihood analysis and parameter estimation. ModeCode is easily extendable to additional models of inflation, and future updates will include Bayesian model comparison. Errors from ModeCode contribute negligibly to the error budget for analyses of data from Planck or other next generation experiments. We constrain representative single-field models (${\varphi }^n$ with $n=2/3$, 1, 2, and 4, natural inflation, and “hilltop” inflation) using current data, and provide forecasts for Planck. From current data, we obtain weak but nontrivial limits on the post-inflationary physics, which is a significant source of uncertainty in the predictions of inflationary models, while we find that Planck will dramatically improve these constraints. In particular, Planck will link the inflationary dynamics with the post-inflationary growth of the horizon, and thus begin to probe the “primordial dark ages” between TeV and grand unified theory scale energies.

The proposed CMBPol mission will be able to detect the imprint of topological defects on the CMB provided the contribution is sufficiently strong. We quantify the detection threshold for cosmic strings and for textures, and analyze the satellite’s ability to distinguish between these different types of defects. We also assess the level of danger of misidentification of a defect signature as from the wrong defect type or as an effect of primordial gravitational waves. A 0.002 fractional contribution of cosmic strings to the CMB temperature spectrum at multipole ten, and similarly a 0.001 fractional contribution of textures, can be detected and correctly identified at the $3\sigma$ level. We also confirm that a tensor contribution of $r=0.0018$ can be detected at over $3\sigma$, in agreement with the CMBPol mission concept study. These results are supported by a model selection analysis.

We show that the popular internal linear combination approach is unstable with respect to division of the observed map pixels to a set of “homogeneous” subsamples. For various choices of such subsamples we can obtain a restored CMB signal with amplitudes ranging from zero to the amplitude of the observed signal. We propose an approach which allows us to obtain corrected estimates of the CMB power spectrum $C_{\ell }$ at $\ell \le 30$ and provides results similar to WMAP for larger $\ell$. Using this approach, we eliminate some anomalies of the WMAP results. In particular, our estimate of the quadrupole is consistent with the theoretically expected one. The effect of the “axis of evil” is suppressed, and the symmetry of the north and south galactic hemispheres increases. These results can change estimates of quadrupole polarization and the redshift of reionization of the Universe. We also propose a new simple approach which can improve the WMAP estimates of the high $\ell$ power spectrum.

We present an improved calculation on the pionic twist-3 distribution amplitudes ${\varphi }_p^{\pi }$ and ${\varphi }_{\sigma }^{\pi }$, which are studied within the QCD sum rules. By adding all the uncertainties in quadrature, it is found that $⟨{\xi }_p^2⟩={0.248}_{-0.052}^{+0.076}$, $⟨{\xi }_p^4⟩={0.262}_{-0.055}^{+0.080}$, $⟨{\xi }_{\sigma }^2⟩={0.102}_{-0.025}^{+0.035}$ and $⟨{\xi }_{\sigma }^4⟩={0.094}_{-0.020}^{+0.028}$. Furthermore, with the help of these moments, we construct a model for the twist-3 wave functions ${\psi }_{p,\sigma }^{\pi }(x,{\mathbf{k}}_{\perp })$, which have better end point behavior and are helpful for perturbative QCD approach. The obtained twist-3 distribution amplitudes are adopted to calculate the $B\to \pi$ transition form factor $f_{B\pi }^{+}$ within the QCD light cone sum rules up to next-to-leading order. By suitable choice of the parameters, we obtain a consistent $f_{B\pi }^{+}$ with those obtained in the literature.

We investigate scenarios in which dark matter is stabilized by an Abelian $Z_N$ discrete gauge symmetry. Models are surveyed according to symmetries and matter content. Multicomponent dark matter arises when $N$ is not prime and $Z_N$ contains one or more subgroups. The dark sector interacts with the visible sector through the renormalizable kinetic mixing and Higgs portal operators, and we highlight the basic phenomenology in these scenarios. In particular, multiple species of dark matter can lead to an unconventional nuclear recoil spectrum in direct detection experiments, while the presence of new light states in the dark sector can dramatically affect the decays of the Higgs at the Tevatron and LHC, thus providing a window into the gauge origin of the stability of dark matter.

We calculate the $O({\alpha }_s)$ corrections to the timelike, spacelike, and double deeply virtual Compton scattering amplitudes in the generalized Bjorken scaling region. Special attention is devoted to studies of the difference between the next-to-leading order timelike and spacelike coefficient functions, which plays for this process a role analogous to the large $K$ factor which was much discussed in the analysis of inclusive Drell-Yan cross sections. Also in the present studies the timelike nature of the hard scale gives rise to a new absorptive part of the amplitude and to the presence of characteristic ${\pi }^2$ terms, which can potentially lead to sizable corrections.

The chiral $SU(3)$ Lagrangian with the baryon octet and decuplet fields is considered. The $Q^2$ counterterms involving the decuplet fields are constructed. We derive the correlation of the chiral parameters implied by the $1/N_c$ expansion at leading order in QCD.

We demonstrate precisely what particle physics information can be extracted from a single direct detection observation of dark matter while making absolutely no assumptions about the local velocity distribution and local density of dark matter. Our central conclusions follow from a very simple observation: the velocity distribution of dark matter is positive definite, $f(v)\ge 0$. We demonstrate the utility of this result in several ways. First, we show a falling deconvoluted recoil spectrum (deconvoluted of the nuclear form factor), such as from ordinary elastic scattering, can be “mocked up” by any mass of dark matter above a kinematic minimum. As an example, we show that dark matter much heavier than previously considered can explain the CoGeNT excess. Specifically, $m_{\chi }<m_{\mathrm{Ge}}$ can be in just as good agreement as light dark matter, while $m_{\chi }>m_{\mathrm{Ge}}$ depends on understanding the sensitivity of xenon to dark matter at very low recoil energies, $E_R\lesssim 6\mathrm{keVnr}$. Second, we show that any rise in the deconvoluted recoil spectrum represents distinct particle physics information that cannot be faked by an arbitrary $f(v)$. As examples of resulting nontrivial particle physics, we show that inelastic dark matter and dark matter with a form factor can both yield such a rise.

We discuss new physics in top-quark interactions, using an effective-field-theory approach. We consider top-quark decay, single top production, and top-quark pair production. We identify 15 dimension-six operators that contribute to these processes, and we compute the deviation from the standard model induced by these operators. The results provide a systematic way of searching for (or obtaining bounds on) physics beyond the standard model.

The Nambu–Jona-Lasinio model with a Kobayashi-Maskawa-’t Hooft term is one low energy effective theory of QCD which includes the $U_A(1)$ anomaly. We investigate nonet meson properties in this model with three flavors of quarks. We employ two types of regularizations, the dimensional and sharp cutoff ones. The model parameters are fixed phenomenologically for each regularization. Evaluating the kaon decay constant, the $\eta$ meson mass and the topological susceptibility, we show the regularization dependence of the results and discuss the applicability of the Nambu–Jona-Lasinio model.

We give minimal values for the smallest lepton mixing parameter $|U_{e3}|$, applying 2-loop renormalization group equations in an effective theory approach. This is relevant in scenarios that predict an inverted neutrino mass spectrum with the smallest mass and $|U_{e3}|$ being zero at tree level, a situation known to be preserved at 1-loop order. At 2-loop, $|U_{e3}|$ is generated at a level of ${10}^{-12}–{10}^{-14}$. Such small values are of interest in supernova physics. Corresponding limits for the normal mass ordering are several orders of magnitude larger. Our results show that $|U_{e3}|$ can in general be expected to be nonzero.

We present an analysis of exclusive charmless semileptonic $B$-meson decays based on $377\times {10}^6$ $B\overline{B}$ pairs recorded with the BABAR detector at the $\mathit{{\rm Y}}(4S)$ resonance. We select four event samples corresponding to the decay modes $B^0\to {\pi }^{-}{\ell }^{+}\nu$, $B^{+}\to {\pi }^0{\ell }^{+}\nu$, $B^0\to {\rho }^{-}{\ell }^{+}\nu$, and $B^{+}\to {\rho }^0{\ell }^{+}\nu$ and find the measured branching fractions to be consistent with isospin symmetry. Assuming isospin symmetry, we combine the two $B\to \pi \ell \nu$ samples, and similarly the two $B\to \rho \ell \nu$ samples, and measure the branching fractions $\mathcal{B}(B^0\to {\pi }^{-}{\ell }^{+}\nu )=(1.41\pm 0.05\pm 0.07)\times {10}^{-4}$ and $\mathcal{B}(B^0\to {\rho }^{-}{\ell }^{+}\nu )=(1.75\pm 0.15\pm 0.27)\times {10}^{-4}$, where the errors are statistical and systematic. We compare the measured distribution in $q^2$, the momentum transfer squared, with predictions for the form factors from QCD calculations and determine the Cabibbo-Kobayashi-Maskawa matrix element $|V_{ub}|$. Based on the measured partial branching fraction for $B\to \pi \ell \nu$ in the range $q^2<12{\mathrm{GeV}}^2$ and the most recent QCD light-cone sum-rule calculations, we obtain $|V_{ub}|=(3.78\pm {0.13}_{-0.40}^{+0.55})\times {10}^{-3}$, where the errors refer to the experimental and theoretical uncertainties. From a simultaneous fit to the data over the full $q^2$ range and the FNAL/MILC lattice QCD results, we obtain $|V_{ub}|=(2.95\pm 0.31)\times {10}^{-3}$ from $B\to \pi \ell \nu$, where the error is the combined experimental and theoretical uncertainty.

We report the result of a search for the rare decay $B^0\to \gamma \gamma$ in $426{\mathrm{fb}}^{-1}$ of data, corresponding to $226\times {10}^6$ $B^0{\overline{B}}^0$ pairs, collected on the ${\rm Y}(4S)$ resonance at the PEP-II asymmetric-energy $e^{+}{e}^{-}$ collider using the BABAR detector. We use a maximum likelihood fit to extract the signal yield and observe ${21}_{-12}^{+13}$ signal events with a statistical significance of $1.8\sigma$. This corresponds to a branching fraction $\mathcal{B}(B^0\to \gamma \gamma )=(1.7\pm 1.1(\mathrm{stat}.)\pm 0.2(\mathrm{syst}.))\times {10}^{-7}$. Based on this result, we set a 90% confidence level upper limit of $\mathcal{B}(B^0\to \gamma \gamma )<3.2\times {10}^{-7}$.

By performing new, long and numerically accurate general-relativistic simulations of magnetized, equal-mass neutron-star binaries, we investigate the role that realistic magnetic fields may have in the evolution of these systems. In particular, we study the evolution of the magnetic fields and show that they can influence the survival of the hypermassive neutron star produced at the merger by accelerating its collapse to a black hole. We also provide evidence that, even if purely poloidal initially, the magnetic fields produced in the tori surrounding the black hole have toroidal and poloidal components of equivalent strength. When estimating the possibility that magnetic fields could have an impact on the gravitational-wave signals emitted by these systems either during the inspiral or after the merger, we conclude that for realistic magnetic-field strengths $B\lesssim {10}^{12}\mathrm{G}$ such effects could be detected, but only marginally, by detectors such as advanced LIGO or advanced Virgo. However, magnetically induced modifications could become detectable in the case of small-mass binaries and with the development of gravitational-wave detectors, such as the Einstein Telescope, with much higher sensitivities at frequencies larger than $\approx 2\mathrm{kHz}$.

Recently, Banados, Silk and West (BSW) showed that the total energy of two colliding test particles has no upper limit in their center of mass frame in the neighborhood of an extreme Kerr black hole, even if these particles were at rest at infinity in the infinite past. We call this mechanism the BSW mechanism or BSW process. The large energy of such particles would generate strong gravity, although this has not been taken into account in the BSW analysis. A similar mechanism is seen in the collision of two spherical test shells in the neighborhood of an extreme Reissner-Nordström black hole. In this paper, in order to draw some implications concerning the effects of gravity generated by colliding particles in the BSW process, we study a collision of two spherical dust shells, since their gravity can be exactly treated. We show that the energy of two colliding shells in the center of mass frame observable from infinity has an upper limit due to their own gravity. Our result suggests that an upper limit also exists for the total energy of colliding particles in the center of mass frame in the observable domain in the BSW process due the gravity of the particles.

The nucleon helicity-independent generalized parton distributions of quarks are calculated in the zero skewness case, in the framework of the anti-de Sitter/QCD model. The present approach is based on a matching procedure of sum rules relating the electromagnetic form factors to generalized parton distributions and anti-de Sitter modes.

We analyze supergravity models that predict a low mass gluino within the landscape of sparticle mass hierarchies. The analysis includes a broad class of models that arise in minimal and in nonminimal supergravity unified frameworks and in extended models with additional $U(1{)}_X^n$ hidden sector gauge symmetries. Gluino masses in the range (350–700) GeV are investigated. Masses in this range are promising for early discovery at the LHC at $\sqrt{s}=7\mathrm{TeV}$ (LHC-7). The models exhibit a wide dispersion in the gaugino-Higgsino eigencontent of their lightest supersymmetric particles and in their associated sparticle mass spectra. A signature analysis is carried out and the prominent discovery channels for the models are identified with most models needing only $\sim 1{\mathrm{fb}}^{-1}$ for discovery at LHC-7. In addition, significant variations in the discovery capability of the low mass gluino models are observed for models in which the gluino masses are of comparable size due to the mass splittings in different models and the relative position of the light gluino within the various sparticle mass hierarchies. The models are consistent with the current stringent bounds from the Fermi-LAT, CDMS-II, XENON100, and EDELWEISS-2 experiments. A subclass of these models, which include a mixed–$w$-ino lightest supersymmetric particle and a Higgsino lightest supersymmetric particle, are also shown to accommodate the positron excess seen in the PAMELA satellite experiment.

An analytic coordinate-space expression for the next-to-leading order photon impact factor for small-$x$ deep inelastic scattering is calculated using the operator expansion in Wilson lines.