Photon spheres, surfaces where massless particles are confined in closed orbits, are expected to be common astrophysical structures surrounding ultracompact objects. In this paper a semiclassical treatment of a photon sphere is proposed. We consider the quantum Maxwell field and derive its energy spectra. A thermodynamic approach for the quantum photon sphere is developed and explored. Within this treatment, an expression for the spectral energy density of the emitted radiation is presented. Our results suggest that photon spheres, when thermalized with their environment, have nonusual thermodynamic properties, which could lead to distinct observational signatures.

Massive complex scalar fields can form bound states around Kerr black holes. These bound states—dubbed scalar clouds—are generically nonzero and finite on and outside the horizon; they decay exponentially at spatial infinity, have a real frequency and are specified by a set of integer “quantum” numbers $(n,l,m)$. For a specific set of these numbers, the clouds are only possible along a one-dimensional subset of the two-dimensional parameter space of Kerr black holes, called an existence line. In this paper we make a thorough investigation of the scalar clouds due to neutral (charged) scalar fields around Kerr(-Newman) black holes. We present the location of the existence lines for a variety of quantum numbers, their spatial representation and compare analytic approximation formulas in the literature with our exact numerical results, exhibiting a sometimes remarkable agreement.

We solve the coupled Einstein-Vlasov system in spherical symmetry using direct numerical integration of the Vlasov equation in phase space. Focusing on the case of massless particles we study critical phenomena in the model, finding strong evidence for generic type I behavior at the black hole threshold that parallels what has previously been observed in the massive sector. For differing families of initial data we find distinct critical solutions, so there is no universality of the critical configuration itself. However we find indications of at least a weak universality in the lifetime scaling exponent, which is yet to be understood. Additionally, we clarify the role that angular momentum plays in the critical behavior in the massless case.

In the Lemaître-Tolman (L-T) models that have nonconstant bang-time function $t_B(r)$, light emitted close to those points of the big bang where $\mathrm{d}{t}_B/\mathrm{d}r\ne 0$ is blueshifted at the receiver position. The blueshifted rays are expected to perturb the temperature of the cosmic microwave background radiation along the lines of sight of the present central observer. It is shown here that, in a general L-T model, the $t_B(r)$ can be chosen so that the blueshift-generating region is hidden before the recombination time, where the L-T model does not apply. The rest of the paper is devoted to investigating blueshifts in one specific L-T model, called $\mathrm{L}\text{−}\mathrm{T}(t_B)$—the one that duplicates the luminosity distance vs redshift relation of the $\mathrm{\Lambda }\mathrm{CDM}$ model using nonconstant $t_B(r)$ alone. The location of the blueshift-generating region in the $\mathrm{L}\text{−}\mathrm{T}(t_B)$ spacetime is determined. Profiles of redshift/blueshift along several rays intersecting the past light cone of the present central observer are calculated. The $\mathrm{L}\text{−}\mathrm{T}(t_B)$ model matched to Friedmann is considered, and profiles of redshift/blueshift in such a composite model are calculated. The requirement of invisibility of blueshifts makes the $\mathrm{L}\text{−}\mathrm{T}(t_B)$ model astrophysically unacceptable if it should apply back to the recombination time, but it does not “rule out” a general L-T model—it only puts limits on $\mathrm{d}{t}_B/\mathrm{d}r$.

We propose to use dynamical symmetries of the field equations, in order to classify the dark energy models in the context of scalar field (quintessence or phantom) Friedmann-Lemaître-Robertson Walker cosmologies. Practically, symmetries provide a useful mathematical tool in physical problems since they can be used to simplify a given system of differential equations as well as to determine the integrability of the physical system. The requirement that the field equations admit dynamical symmetries results in two potentials, one of which is the well-known unified dark matter potential and another new potential. For each hyperbolic potential we obtain the corresponding analytic solution of the field equations. The proposed analysis suggests that the requirement of the contact symmetry appears to be very competitive to other independent tests used to probe the functional form of a given potential and thus the associated nature of dark energy. Finally, in order to test the viability of the above scalar field models we perform a joint likelihood analysis using some of the latest cosmological data.

We present a generalization of a model where the right-handed up-type quarks serve as messengers for neutrino mass generation and as a portal for dark matter. Within this framework, the Standard Model is extended with a single Majorana neutrino, a colored electroweak-singlet scalar, and a colored electroweak-triplet scalar. We calculate the relic abundance of dark matter and show that we can match the latest experimental results. Furthermore, the implications from the scattering between nuclei and the dark matter candidate are studied, and we implement the latest experimental constraints arising from flavor changing interactions, Higgs production and decay, and LHC collider searches for a single jet and jets plus missing energy. In addition, we implement constraints arising from scalar top quark pair production. We also study the production of a single top in association with missing energy and calculate the sensitivity of the LHC to the top quark semileptonic decay mode with the current ${20\mathrm{fb}}^{-1}$ data set at a center-of-mass energy of $\sqrt{s}=8\mathrm{TeV}$. Furthermore, we carry out the analysis to center-of-mass energies of $\sqrt{s}=14\mathrm{TeV}$ with 30 and $300{\mathrm{fb}}^{-1}$ of data.

We present a model independent analysis of inelastic dark matter transitions at direct detection experiments by modifying the elastic methodology of Fitzpatrick et al. By analyzing the kinematics of inelastic transitions, we find the relevant variables to describe these scattering processes, the primary change being a modification of the ${\overrightarrow{v}}^{\perp }$ variable. Taking this into account, we list the relevant scattering matrix elements and modify the Mathematica package of Anand et al. to calculate the necessary form factors. As an application, we determine the matrix elements of inelastic scattering for spin transitions between a fermion to fermion, scalar to vector, and scalar to scalar. Finally, we consider fits to the DAMA/LIBRA annual modulation signal for the magnetic inelastic dark matter scenario as well as a model independent scan over relativistic operators, constraining them with limits from direct detection experiments. In the magnetic inelastic dark matter scenario or if the dark matter couples through relativistic operators involving only protons, we find that experiments with xenon and germanium targets can have consistently small rates. However, limits from iodine experiments are much more constraining, leaving small regions of allowed parameter space. We point out that existing uncertainties in the iodine quenching factor strongly affects the constraints, motivating further study to pin down the correct values.

We determine the $R$ ratio for massless quarks in several renormalization schemes to various loop orders. These are the momentum subtraction schemes of Celmaster and Gonsalves as well as the minimal momentum subtraction scheme. The dependence of the $R$ ratio on the schemes is analyzed.

The production of top quark-antiquark pair events in $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$ is studied as a function of the transverse momentum and absolute value of the rapidity of the top quarks as well as of the invariant mass of the $t\overline{t}$ pair. We select events containing an isolated lepton, a large imbalance in transverse momentum, and four or more jets with at least one jet identified as originating from a $b$ quark. The data sample corresponds to $9.7{\mathrm{fb}}^{-1}$ of integrated luminosity recorded with the D0 detector during Run II of the Fermilab Tevatron Collider. Observed differential cross sections are consistent with standard model predictions.

The archetypal theory of dark energy is quintessence: a minimally coupled scalar field with a canonical kinetic energy and potential. By studying random potentials, we show that quintessence imposes a restricted set of priors on the equation of state of dark energy. Focusing on the commonly used parametrization, $w(a)\approx w_0+w_a(1-a)$, we show that there is a natural scale and direction in the $(w_0,w_a)$ plane that distinguishes quintessence as a general framework. We calculate the expected information gain for a given survey and show that, because of the nontrivial prior information, it is a function of more than just the figure of merit. This allows us to make a quantitative case for novel survey strategies. We show that the scale of the prior sets target observational requirements for gaining significant information. This corresponds to a figure of merit $\mathrm{FOM}\gtrsim 200$, a requirement that future galaxy redshift surveys will meet.

We analyze the dynamical evolution of a perturbed force-free magnetosphere of a rotating black hole, which is described by the Blandford-Znajek solution in the stationary limit. We find that the electromagnetic field perturbations can be classified into two categories: “trapped modes” and “traveling waves.” The trapped modes are analogous to the vacuum (without plasma) electromagnetic quasinormal modes in rotating black hole spacetimes, but with different eigenfrequencies and wave functions, due to their coupling with the background electromagnetic field and current. The traveling waves propagate freely to infinity or the black hole horizon along specific null directions, and they are closely related to the no-scattering Poynting flux solutions discovered by Brennan, Gralla and Jacobson. Our results suggest that the Blandford-Znajek solution is mode stable, and more importantly we expect this study to illuminate the dynamical behavior of force-free magnetospheres as well as to shed light on the path to new exact solutions.

We study how rapid rotation influences the relation between the normalized moment of inertia $\overline{I}$ and quadrupole moment $\overline{Q}$ for scalarized neutron stars. The questions one has to answer are whether the equation of state universality is preserved in this regime and what are the deviations from general relativity. Our results show that the $\overline{I}-\overline{Q}$ relation is nearly equation of state independent for scalarized rapidly rotating stars, but the differences with pure Einstein’s theory increase compared to the slowly rotating case. In general, smaller negative values of the scalar field coupling parameters $\beta$ lead to larger deviations, but these deviations are below the expected accuracy of the future astrophysical observations if one considers values of $\beta$ in agreement with the current observational constraints. An important remark is that although the normalized $\overline{I}-\overline{Q}$ relation is quite similar for scalar-tensor theories and general relativity, the unnormalized moment of inertia and quadrupole moment can be very different in the two theories. This demonstrates that although the $\overline{I}-\overline{Q}$ relations are potentially very useful for some purposes, they might not serve us well when trying to distinguish between different theories of gravity.

In this paper, we investigate the critical behavior of charged black holes of Einstein-Maxwell-dilaton gravity in the presence of two Liouville-type potentials which make the solution asymptotically neither flat nor AdS and has a parameter $\mathrm{\Lambda }$ treated as a thermodynamic quantity that can vary. We obtain a Smarr-type relation for charged dilatonic black holes and find out that the volume is different from the geometrical volume. We study the analogy of the Van der Waals liquid-gas system with the charged dilatonic black hole system, while we treat the black hole charge as a fixed external parameter. Moreover, we show that the critical values for pressure, temperature, and volume are physical provided the coupling constant of dilaton gravity is less than one and the horizon is a sphere. Finally, we calculate the critical exponents and show that they are universal and are independent of the details of the system although the thermodynamic quantities depend on the dilaton parameter and the dimension of the spacetime.

We explicitly compute the dynamics of closed homogeneous and isotropic universes permeated by a single perfect fluid with a constant equation-of-state parameter $w$ in the context of a recent reformulation of general relativity, proposed by Kaloper and Padilla [Phys. Rev. Lett. 112, 091304 (2014)], which prevents the vacuum energy from acting as a gravitational source. This is done using an iterative algorithm, taking as an initial guess the background cosmological evolution obtained using standard general relativity in the absence of a cosmological constant. We show that, in general, the impact of the vacuum energy sequestering mechanism on the dynamics of the universe is significant, except for the $w=1/3$ case where the results are identical to those obtained in the context of general relativity with a null cosmological constant. We also show that there are well-behaved models in general relativity that do not have a well-behaved counterpart in the vacuum energy sequestering paradigm studied in this paper, highlighting the specific case of a quintessence scalar field with a linear potential.

We have made core-collapse supernova simulations that allow oscillations between electron neutrinos (or their antiparticles) with right-handed sterile neutrinos. We have considered a range of mixing angles and sterile neutrino masses including those consistent with sterile neutrinos as a dark matter candidate. We examine whether such oscillations can impact the core bounce and shock reheating in supernovae. We identify the optimum ranges of mixing angles and masses that can dramatically enhance the supernova explosion by efficiently transporting electron antineutrinos from the core to behind the shock, where they provide additional heating leading to much larger explosion kinetic energies. We show that this effect can cause stars to explode that otherwise would have collapsed. We find that an interesting periodicity in the neutrino luminosity develops due to a cycle of depletion of the neutrino density by conversion to sterile neutrinos that shuts off the conversion, followed by a replenished neutrino density as neutrinos transport through the core.

We study the collision of two particles with equal masses moving in the equatorial plane near the horizon of the rotating regular Ayón-Beato-García (ABG) black hole (BH) and calculate the center-of-mass (CM) energy for the colliding particles for both extremal and nonextremal cases. It turns out that CM energy depends not only on rotation parameter $a$ but also on charge $Q$. Particularly for the extremal rotating regular ABG BH, the CM energy of two colliding particles could be arbitrarily high for the critical angular momentum of particles. Furthermore, we also show that, for a nonextremal BH, there exists a finite upper limit of CM energy, which changes with charge $Q$. A comparison with Kerr and Kerr-Newman black holes is included.

We report the results of a new experimental setup to measure the mechanical loss of coating layers on a thin sapphire disk at cryogenic temperatures. Some of the authors previously reported that there was no temperature dependence of the mechanical loss from a multilayer tantala/silica coating on a sapphire disk, both before and after heat treatment, although some reports indicate that ${\mathrm{Ta}}_2{\mathrm{O}}_5$ and ${\mathrm{SiO}}_2$ layers annealed at $600°\mathrm{C}$ have loss peaks near 20 K. Since KAGRA—the Japanese gravitational-wave detector, currently under construction—will be operated at 20 K and have coated sapphire mirrors, it is very important to clarify the mechanical loss behavior of tantala/silica coatings around this temperature. We carefully investigate a tantala/silica-coated sapphire disk with the new setup, anneal the disk, and then investigate the annealed disk. We find that there is no distinct loss peak both before and after annealing under particular conditions. The mechanical loss for the unannealed disk at 20 K is about $5\times {10}^{-4}$, as previously reported, while that for the annealed disk is approximately $6.4\times {10}^{-4}$.

The parameter space of the minimal supersymmetric standard model (MSSM) can be probed via many avenues, such as by precision measurements of the couplings of the $\sim 126\mathrm{GeV}$ Higgs boson, as well as the direct searches for supersymmetry (SUSY) partners. We examine the connection between these two collider observables at the LHC and International Linear Collider (ILC) in the $19/20$-parameter phenomenological MSSM (pMSSM). Within this scenario, we address two questions: (i) How will potentially null direct searches for SUSY at the LHC influence the predicted properties of the lightest SUSY Higgs boson? (ii) What can be learned about the properties of the superpartners from precision measurements of the Higgs boson couplings? In this paper, we examine these questions by employing three different large sets of pMSSM models with either the neutralino or gravitino being the lightest supersymmetric particle. We make use of the ATLAS direct SUSY searches at the $7/8\mathrm{TeV}$ LHC as well as expected results from 14 TeV operations, and the anticipated precision measurements of the Higgs boson couplings at the 14 TeV LHC and at the ILC. We demonstrate that the future Higgs coupling determinations can deeply probe the pMSSM parameter space and, in particular, can observe the effects of models that are projected to evade the direct searches at the 14 TeV LHC with $3{\mathrm{ab}}^{-1}$ of integrated luminosity. In addition, we compare the reach of the Higgs coupling determinations to the direct heavy Higgs searches in the $M_A-\tan \beta$ plane and show that they cover orthogonal regions. This analysis demonstrates the complementarity of the direct and indirect approaches in searching for supersymmetry, and the importance of precision studies of the properties of the Higgs boson.

We consider a simple supersymmetric hidden sector: pure $\mathrm{SU}(N)$ gauge theory. Dark matter is made up of hidden glueballinos with mass $m_X$ and hidden glueballs with mass near the confinement scale $\mathrm{\Lambda }$. For $m_X\sim 1\mathrm{TeV}$ and $\mathrm{\Lambda }\sim 100\mathrm{MeV}$, the glueballinos freeze out with the correct relic density and self-interact through glueball exchange to resolve small-scale structure puzzles. An immediate consequence is that the glueballino spectrum has a hyperfine splitting of order ${\mathrm{\Lambda }}^2/m_X\sim 10\mathrm{keV}$. We show that the radiative decays of the excited state can explain the observed 3.5 keV x-ray line signal from clusters of galaxies, Andromeda, and the Milky Way.