Quantum fluctuations of matter fields contribute to the thermal entropy of black holes. For free minimally coupled scalar and spinor fields, this contribution is precisely the entanglement entropy. For gauge fields, Kabat found an extra negative divergent “contact term” with no known statistical interpretation. We compare this contact term to a similar term which arises for nonminimally coupled scalar fields. Although both divergences may be interpreted as terms in the Wald entropy, we point out that the contact term for gauge fields comes from a gauge-dependent ambiguity in Wald’s formula. Revisiting Kabat’s derivation of the contact term, we show that it is sensitive to the treatment of infrared modes. To explore these infrared issues, we consider two-dimensional compact manifolds, such as Euclidean de Sitter space, and show that the contact term arises from an incorrect treatment of zero modes. In a manifestly gauge-invariant reduced phase space quantization, the gauge field contribution to the entropy is positive, finite, and equal to the entanglement entropy.

We show that strictly stationary spacetimes cannot have nontrivial configurations of form fields/complex scalar fields. This means that the spacetime should be exactly Minkowski or anti-deSitter spacetime depending on the presence of negative cosmological constant. That is, self-gravitating complex scalar fields and form fields cannot exist.

In Dirac-Born-Infeld inflation, changes in the sound speed that transiently break the slow-roll approximation lead to features in the power spectrum. We develop and test the generalized slow-roll approximation for calculating such effects and show that it can be extended to treat order unity features. As in slow-roll, model independent constraints on the potential of canonical inflation can be directly reinterpreted in the Dirac-Born-Infeld context through this approximation. In particular, a sharp horizon scale step in the warped brane tension can explain oscillatory features in the WMAP7 CMB power spectrum as well as features in the potential. Differences appear only as a small suppression of power on horizon scales and larger.

We consider a simple class of models in which the dark matter, $X$, is coupled to a new gauge boson, $\varphi$, with a relatively low mass ($m_{\varphi }\sim 100\mathrm{MeV}–3\mathrm{GeV}$). Neither the dark matter nor the new gauge boson have tree-level couplings to the Standard Model. The dark matter in this model annihilates to $\varphi$ pairs, and for a coupling of $g_X\approx 0.06\times (m_X/10\mathrm{GeV}{)}^{1/2}$ yields a thermal relic abundance consistent with the cosmological density of dark matter. The $\varphi$’s produced in such annihilations decay through a small degree of kinetic mixing with the photon to combinations of Standard Model leptons and mesons. For dark matter with a mass of $\sim 10\mathrm{GeV}$, the shape of the resulting gamma-ray spectrum provides a good fit to that observed from the Galactic center, and can also provide the very hard electron spectrum required to account for the observed synchrotron emission from the Milky Way’s radio filaments. For kinetic mixing near the level naively expected from loop-suppressed operators ($ϵ\sim {10}^{-4}$), the dark matter is predicted to scatter elastically with protons with a cross section consistent with that required to accommodate the signals reported by DAMA/LIBRA, CoGeNT and CRESST-II.

The differential $p_T$ spectrum for vector boson production is computed at next-to-leading fixed order and including the resummation of threshold logarithms at next-to-next-to-leading logarithmic accuracy. A comparison is made to atlas data on direct photon and $W$ production at high transverse momentum $p_T$, finding excellent agreement. The resummation is achieved by factorizing contributions associated with different scales using soft-collinear effective theory. Each part is then calculated perturbatively and the individual contributions are combined using renormalization group methods. A key advantage of the effective theory framework is that it indicates a set of natural scale choices, in contrast to the fixed-order calculation. Resummation of logarithms of ratios of these scales leads to better agreement with data and reduced theoretical uncertainties.

In this work, we present a systematic study of the observed isoscalar tensor $f_2$ states. With the detailed analysis of the mass spectrum and calculation of the $f_2$ two-body strong decays, we extract information from their underlying structures and try to categorize them into the conventional tensor meson family [$n{}^{3}P_2$ ($n=1$, 2, 3, 4) and $m{}^{3}F_2$ ($m=1$, 2)]. We also give predictions for other decay modes of these tensor mesons, which are useful for further experimental investigations.

All the available experimental information on open charm and beauty mesons is used to classify the observed states in heavy quark doublets. The masses of some of the still unobserved states are predicted, in particular in the beauty sector. Adopting an effective Lagrangian approach based on the heavy quark and chiral symmetry, individual decay rates and ratios of branching fractions are computed, with results useful to assign the quantum numbers to recently observed charmed states which still need to be properly classified. Implications and predictions for the corresponding beauty mesons are provided. The experimental results are already copious, and are expected to grow up thanks to the experiments at the LHC and to the future high-luminosity flavor and $p-\overline{p}$ facilities.

We use $429{\mathrm{fb}}^{-1}$ of $e^{+}{e}^{-}$ collision data collected at the ${\rm Y}(4S)$ resonance with the BABAR detector to measure the radiative transition rate of $b\to s\gamma$ with a sum of 38 exclusive final states. The inclusive branching fraction with a minimum photon energy of 1.9 GeV is found to be $\mathcal{B}(\overline{B}\to X_s\gamma )=(3.29\pm 0.19\pm 0.48)\times {10}^{-4}$ where the first uncertainty is statistical and the second is systematic. We also measure the first and second moments of the photon energy spectrum and extract the best-fit values for the heavy-quark parameters, $m_b$ and ${\mu }_{\pi }^2$, in the kinetic and shape function models.

Using a data sample of $1.06\times {10}^8$ ${\psi }^{\prime }$ events collected with the BESIII detector in 2009, the branching fractions of ${\chi }_{cJ}\to p\overline{n}{\pi }^{-}$ and ${\chi }_{cJ}\to p\overline{n}{\pi }^{-}{\pi }^0$ ($J=0$, 1, 2) are measured. (Throughout the text, inclusion of charge conjugate modes is implied if not stated otherwise.) The results for ${\chi }_{c0}\to p\overline{n}{\pi }^{-}$ and ${\chi }_{c2}\to p\overline{n}{\pi }^{-}$ are consistent with, but much more precise than, those of previous measurements. The decays of ${\chi }_{c1}\to p\overline{n}{\pi }^{-}$ and ${\chi }_{cJ}\to p\overline{n}{\pi }^{-}{\pi }^0$ are observed for the first time.

The transverse momentum cross section of $e^{+}{e}^{-}$ pairs in the $Z$-boson mass region of $66–116\mathrm{GeV}/c^2$ is precisely measured using Run II data corresponding to $2.1{\mathrm{fb}}^{-1}$ of integrated luminosity recorded by the Collider Detector at Fermilab. The cross section is compared with two quantum chromodynamic calculations. One is a fixed-order perturbative calculation at $\mathcal{O}({\alpha }_s^2)$, and the other combines perturbative predictions at high transverse momentum with the gluon resummation formalism at low transverse momentum. Comparisons of the measurement with calculations show reasonable agreement. The measurement is of sufficient precision to allow refinements in the understanding of the transverse momentum distribution.

We present a search for microwave emission from air showers induced by ultrahigh energy cosmic rays with the microwave detection of air showers experiment. No events were found, ruling out a wide range of power flux and coherence of the putative emission, including those suggested by recent laboratory measurements.

We present a measurement of the top-quark mass ($m_t$) in $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$ using $t\overline{t}$ events with two leptons ($ee$, $e\mu$, or $\mu \mu$) and accompanying jets in $4.3{\mathrm{fb}}^{-1}$ of data collected with the D0 detector at the Fermilab Tevatron collider. We analyze the kinematically underconstrained dilepton events by integrating over their neutrino rapidity distributions. We reduce the dominant systematic uncertainties from the calibration of jet energy using a correction obtained from $t\overline{t}$ events with a final state of a single lepton plus jets. We also correct jets in simulated events to replicate the quark flavor dependence of the jet response in data. We measure $m_t=173.7\pm 2.8(\mathrm{stat})\pm 1.5(\mathrm{syst})\mathrm{GeV}$ and combining with our analysis in $1{\mathrm{fb}}^{-1}$ of preceding data we measure $m_t=174.0\pm 2.4(\mathrm{stat})\pm 1.4(\mathrm{syst})\mathrm{GeV}$. Taking into account statistical and systematic correlations, a combination with the D0 matrix element result from both data sets yields $m_t=173.9\pm 1.9(\mathrm{stat})\pm 1.6(\mathrm{syst})\mathrm{GeV}$.

Recently, questions have been raised about the role of Lorentz invariance in false vacuum decay. It has been argued that infinities may arise in an integration over Lorentz-boosted final states. This suggestion motivates a Minkowski-space analysis of the decay rate. We attempt to illuminate features of the amplitude computation, and argue that the total rate including excitations is both finite and Lorentz-invariant.

We analyze the effect of scheme transformations in the vicinity of an exact or approximate infrared fixed point in an asymptotically free gauge theory with fermions. We show that there is far less freedom in carrying out such scheme transformations in this case than at an ultraviolet fixed point. We construct a transformation from the $\overline{\mathrm{MS}}$ scheme to a scheme with a vanishing three-loop term in the $\beta$ function and use this to assess the scheme dependence of an infrared fixed point in $\mathrm{SU}(N)$ theories with fermions. Implications for the anomalous dimension of the fermion bilinear operator are also discussed.

The quark gluon plasma (QGP) at zero temperature and high baryon number is a system that may be present inside compact stars. It is quite possible that this cold QGP shares some relevant features with the hot QGP observed in heavy ion collisions, being also a strongly interacting system. In a previous work we have derived from the QCD Lagrangian an equation of state (EOS) for the cold QGP, which can be considered an improved version of the MIT bag-model EOS. Compared to the latter, our EOS reaches higher values of the pressure at comparable baryon densities. This feature is due to perturbative corrections and also to nonperturbative effects. Here we apply this EOS to the study of neutron stars, discussing the absolute stability of quark matter and computing the mass-radius relation for self-bound (strange) stars. The maximum masses of the sequences exceed two solar masses, in agreement with the recently measured values of the mass of the pulsar PSR J1614-2230, and the corresponding radii of around 10–11 km.

We undertake the study of the charged Higgs bosons predicted by the model with gauge symmetry $SU(3{)}_c\otimes SU(3{)}_L\otimes U(1{)}_X$. By considering Yukawa mixing couplings between small ($\sim \mathrm{GeV}$) and large ($\sim \mathrm{TeV}$) scales, we show that the hypercharge-1 ($H_1^{\pm }$) and hypercharge-2 ($H_2^{\pm }$) Higgs bosons predicted by the model can be simultaneously produced in $pp$ collisions at different production rates. At low energy, the $H_1^{\pm }$ bosons exhibit the same properties as the charged Higgs bosons from a two Higgs doublet model, while $H_2^{\pm }$ are additional like-charged Higgs bosons from the underlying 3-3-1 model. Thus, the identification of multiple like-charged Higgs boson resonances may test the compatibility of theoretical models with experimental data. We study $H_{1,2}^{\pm }$ pairs and associated $tb{H}_{1,2}^{\pm }$ productions at the CERN LHC. In particular, we obtain that pair production can be as large as the single production in gluon-gluon collisions due to the interchange of a heavy neutral $Z^{\prime }$ gauge boson predicted by the model. By considering decays to leptons $H_{1,2}^{\pm }\to \tau {\nu }_{\tau }$, we obtain scenarios where small peaks of $H_2^{\pm }$-boson events in transverse mass distributions can be identified over the $H_1^{\pm }$ background.

We study a Casimir-like behavior in a “deformed QCD.” We demonstrate that for the system defined on a manifold of size $\mathbb{L}$, the difference $\Delta E\equiv E-E_{\mathrm{Mink}}$ between the energies of a system in a nontrivial background and Minkowski space-time geometry exhibits the Casimir-like scaling $\Delta E\sim {\mathbb{L}}^{-1}$, despite the presence of a mass gap in the system, in contrast with naive expectation $\Delta E\sim \exp (-m\mathbb{L})$, which would normally originate from any physical massive propagating degrees of freedom consequent to conventional dispersion relations. The Casimir-like behavior in our system comes instead from a nondispersive (“contact”) term which is not related to any physical propagating degrees of freedom, such that the naive argument is simply not applicable. These ideas can be explicitly tested in weakly coupled deformed QCD. We comment on profound consequences for cosmology of this effect if it persists in real strongly coupled QCD.

Recent results from short-baseline neutrino oscillation experiments suggest the presence of additional sterile neutrinos, while cosmic microwave background anisotropy measurements point toward an excess of radiation, which could in fact be provided by light sterile neutrino states. In this paper we properly combine these two data sets (short-baseline and cosmic microwave background) to derive bounds on the sterile neutrino masses in the $3+1$ and $3+2$ schemes, finding a potentially good agreement between the two data sets. However, when data on galaxy clustering are further included in the analysis, a tension between the oscillation and cosmological data is clearly present. From our combined global analysis the allowed 95% C.L. mass intervals for the additional sterile neutrino states are: $0.85\mathrm{eV}<m_4<1.18\mathrm{eV}$ for the $3+1$ scheme, and $m_4<0.70\mathrm{eV}$ and $0.67\mathrm{eV}<m_5<1.35\mathrm{eV}$ for the $3+2$ scheme.

The presence and evolution of apparent horizons in a two-parameter family of spherically symmetric, time-dependent solutions of Brans-Dicke gravity are analyzed. These solutions were introduced to model space- and time-varying gravitational couplings and are supposed to represent central objects embedded in a spatially flat universe. We find that the solutions possess multiple evolving apparent horizons, both black hole horizons covering a central singularity and cosmological ones. It is not uncommon for two of these horizons to merge, leaving behind a naked singularity covered only by a cosmological horizon. Two characteristic limits are also explicitly worked out: the limit where the theory reduces to general relativity and the limit where the solutions become static. The physical relevance of this family of solutions is discussed.