In this paper, we study gauged solutions associated with a massive vector field representing a spin-1 condensate, namely, the Proca field. We focus on regular spherically symmetric solutions which we construct either using a self-interaction potential or general relativity in order to glue the solutions together. We start generating nongravitating solutions—so-called Proca $Q$-balls and charged Proca $Q$-balls. Then we turn on backreaction on the metric, allowing gravity to hold together the Proca condensate, to study the so-called Proca stars, charged Proca stars, Proca $Q$-stars, and charged Proca $Q$-stars.

We drastically simplify the problem of linearizing a general higher-order theory of gravity. We reduce it to the evaluation of its Lagrangian on a particular Riemann tensor depending on two parameters, and the computation of two derivatives with respect to one of those parameters. We use our method to construct a $D$-dimensional cubic theory of gravity which satisfies the following properties: (1) it shares the spectrum of Einstein gravity, i.e., it only propagates a transverse and massless graviton on a maximally symmetric background; (2) it is defined in the same way in general dimensions; (3) it is neither trivial nor topological in four dimensions. Up to cubic order in curvature, the only previously known theories satisfying the first two requirements are the Lovelock ones. We show that, up to cubic order, there exists only one additional theory satisfying requirements (1) and (2). Interestingly, this theory is, along with Einstein gravity, the only one which also satisfies (3).

We modify the Randall-Sundrum model of braneworld (with two branes) by adding the scalar curvature squared term in five dimensions. We find that it does not destabilize the Randall-Sundrum solution to the hierarchy problem of the standard model in particle physics.

With 91 months of the publicly available Fermi LAT Pass 8 data, we analyze the gamma-ray emission from the Milky Way satellites to search for potential line signals due to the annihilation of dark matter particles into double photons. The searched targets include a sample of dwarf spheroidal galaxies, the Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC). No significant line emission has been found in the stacked dwarf galaxy sample or in the direction of LMC/SMC. The corresponding upper limits on the cross section of DM annihilation into two photons are derived. Compared with results of previous gamma-ray line searches with the Pass 7 data, the current constraints on the line emission from dwarf spheroidal galaxies have been significantly improved in a wide energy range. With the rapid increase of the sample of dwarf spheroidal galaxies (candidates), we expect that the sensitivity of gamma-ray line searches will be significantly improved in the near future.

Miraculously, target-mass corrections for inclusive deep inelastic scattering can be calculated exactly. On the contrary, there does not exist a consistent derivation of kinematic hadron mass corrections for semi-inclusive deep inelastic scattering. Recently this has become of topical interest, since there is a significant difference between the measured HERMES and COMPASS pion and kaon multiplicities, which cannot be explained as a consequence of evolution in $Q^2$, and it has been suggested that the difference can be understood if kinematic hadron mass corrections are taken into account. We explain why this argument is incorrect.

The quest for new heavy states is a critical component of the LHC physics program. In this paper, we study the search for pseudoscalar bosons produced in association with a $t\overline{t}$ pair. We consider the final state $t\overline{t}A\to t\overline{t}b\overline{b}$ with a dileptonic top-pair signature, and reconstruct the boosted $A\to b\overline{b}$ candidate with jet substructure techniques, achieving a remarkable sensitivity over a broad range of pseudoscalar masses and Yukawa couplings. We apply this strategy to a type-I two-Higgs-doublet model (2HDM), demonstrating its ability to probe a realistic, UV-complete extended Higgs sector. In particular, we find that the 13 TeV LHC with $300{\mathrm{fb}}^{-1}$ of data can constrain the region $\tan \beta >1.5$ at 95% C.L. for a light pseudoscalar with $m_A=50\mathrm{GeV}$. Moreover, the whole mass range $20\mathrm{GeV}<m_A<210\mathrm{GeV}$ can be ruled out for $\tan \beta \le 1$. Finally, we show that it is also possible to directly probe the $CP$-structure of the heavy scalar, and hence to distinguish a $CP$-odd ($A$) from a $CP$-even ($H$) 2HDM resonance.

Extensions of the standard model with universal extra dimensions are interesting both as phenomenological templates as well as model-building fertile ground. For instance, they are one of the prototypes for theories exhibiting compressed spectra, leading to difficult searches at the LHC since the decay products of new states are soft and immersed in a large standard model background. Here we study the phenomenology at the LHC of theories with two universal extra dimensions. We obtain the current bound by using the production of second level excitations of electroweak gauge bosons decaying to a pair of leptons and study the reach of the LHC Run II in this channel. We also introduce a new channel originating in higher dimensional operators and resulting in the single production of a second level quark excitation. Its subsequent decay into a hard jet and lepton pair resonance would allow the identification of a more model-specific process, unlike the more generic vector resonance signal. We show that the sensitivity of this channel to the compactification scale is very similar to the one obtained using the vector resonance.

We study some aspects of perturbation theory in $N=1$ supersymmetric Abelian gauge theories with massive charged matter. In general gauges, infrared (IR) divergences and nonlocal behavior arise in one particle irreducible (1PI) diagrams, associated with a $1/k^4$ term in the propagator for the vector superfield. We examine this structure in supersymmetric QED. The IR divergences are gauge dependent and must cancel in physical quantities like the electron pole mass. We demonstrate that cancellation takes place in a nontrivial way, amounting to a reorganization of the perturbative series from powers of $e^2$ to powers of $e$. We also show how these complications are avoided in cases where a Wilsonian effective action can be defined.

In this paper, we perform a full next-to-leading order (NLO) QCD calculation of neutralino scattering on protons or neutrons in the minimal supersymmetric standard model. We match the results of the NLO QCD calculation to the scalar and axial-vector operators in the effective field theory approach. These govern the spin-independent and spin-dependent detection rates, respectively. The calculations have been performed for general bino, wino and higgsino decompositions of neutralino dark matter and required a novel tensor reduction method of loop integrals with vanishing relative velocities and Gram determinants. Numerically, the NLO QCD effects are shown to be of at least of similar size and sometimes larger than the currently estimated nuclear uncertainties. We also demonstrate the interplay of the direct detection rate with the relic density when consistently analyzed with the program dm@nlo.

We perform a systematic, large-scale lattice simulation of D0-brane quantum mechanics. The large-$N$ and continuum limits of the gauge theory are taken for the first time at various temperatures $0.4\le T\le 1.0$. As a way to test the gauge/gravity duality conjecture we compute the internal energy of the black hole as a function of the temperature directly from the gauge theory. We obtain a leading behavior that is compatible with the supergravity result $E/N^2=7.41T^{14/5}$: the coefficient is estimated to be $7.4\pm 0.5$ when the exponent is fixed and stringy corrections are included. This is the first confirmation of the supergravity prediction for the internal energy of a black hole at finite temperature coming directly from the dual gauge theory. We also constrain stringy corrections to the internal energy.

We revisit the suggestion that charged $\rho$-mesons undergo Bose-Einstein condensation in isospin-rich nuclear matter. Using a simple version of the Nambu–Jona-Lasinio (NJL) model, we conclude that $\rho$-meson condensation is either avoided or postponed to isospin chemical potentials much higher than the $\rho$-meson mass as a consequence of the repulsive interaction with the preformed pion condensate. In order to support our numerical results, we work out a linear sigma model for pions and $\rho$-mesons, showing that the two models lead to similar patterns of medium dependence of meson masses. As a byproduct, we analyze in detail the mapping between the NJL model and the linear sigma model, focusing on conditions that must be satisfied for a quantitative agreement between the models.

We compute the transport coefficients, namely, the coefficients of shear and bulk viscosity, as well as thermal conductivity, for hot and dense quark matter. The calculations are performed within the Nambu–Jona-Lasinio (NJL) model. The estimation of the transport coefficients is made using a quasiparticle approach of solving the Boltzmann kinetic equation within the relaxation time approximation. The transition rates are calculated in a manifestly covariant manner to estimate the thermal-averaged cross sections for quark-quark and quark-antiquark scattering. The calculations are performed for finite chemical potential also. Within the parameters of the model, the ratio of shear viscosity to entropy density has a minimum at the Mott transition temperature. At vanishing chemical potential, the ratio of bulk viscosity to entropy density, on the other hand, decreases with temperature, with a sharp decrease near the critical temperature, and vanishes beyond it. At finite chemical potential, however, it increases slowly with temperature beyond the Mott temperature. The coefficient of thermal conductivity also shows a minimum at the critical temperature.

We perform a low-mass dark matter search using an exposure of $30\mathrm{kg}\times \mathrm{yr}$ with the XENON100 detector. By dropping the requirement of a scintillation signal and using only the ionization signal to determine the interaction energy, we lowered the energy threshold for detection to 0.7 keV for nuclear recoils. No dark matter detection can be claimed because a complete background model cannot be constructed without a primary scintillation signal. Instead, we compute an upper limit on the WIMP-nucleon scattering cross section under the assumption that every event passing our selection criteria could be a signal event. Using an energy interval from 0.7 keV to 9.1 keV, we derive a limit on the spin-independent WIMP-nucleon cross section that excludes WIMPs with a mass of $6\mathrm{GeV}/c^2$ above $1.4\times {10}^{-41}{\mathrm{cm}}^2$ at 90% confidence level.

We study the shear viscosity in an effective hydrodynamic theory and holographic model where the translational symmetry is broken by massless scalar fields. We identify the shear viscosity, $\eta$, from the coefficient of the shear tensor in the modified constitutive relation, constructed from thermodynamic quantities, fluid velocity, and the scalar fields, which break the translational symmetry explicitly. Our construction of constitutive relation is inspired by those derived from the fluid/gravity correspondence in the weakly disordered limit $m/T\ll 1$. We show that the shear viscosity from the constitutive relation deviates from the one obtained from the usual expression, ${\eta }^{\star }=-\underset{\omega \to 0}{\lim }(1/\omega )\mathrm{Im}{G}_{T^{xy}{T}^{xy}}^R(\omega ,k=0)$, even at the leading order in disorder strength. In a simple holographic model with broken translational symmetry, we show that both $\eta /s$ and ${\eta }^{\star }/s$ violate the bound of the viscosity-entropy ratio for arbitrary disorder strength.

The goal of this paper is to extend to higher dimensionality the methods and computations of vacuum polarization effects in black hole spacetimes. We focus our attention on the case of five dimensional Schwarzschild-Tangherlini black holes, for which we adapt the general method initially developed by Candelas and later refined by Anderson and others. We make use of point splitting regularization and of the WKB approximation to extract the divergences occurring in the coincidence limit of the Green function and, after calculating the counterterms using the Schwinger–De Witt expansion, we explicitly prove the cancellation of the divergences and the regularity of the vacuum polarization once counterterms are added up. We finally handle numerically the renormalized expression of the vacuum polarization. As a check on the method we also prove the regularity of the vacuum polarization in the six dimensional case in the large mass limit.

We derive the asymptotic solutions for vacuum spacetimes with nonzero cosmological constant $\mathrm{\Lambda }$, using the Newman-Penrose formalism. Our approach is based exclusively on the physical spacetime, i.e., we do not explicitly deal with conformal rescaling nor the conformal spacetime. By investigating the Schwarzschild-de Sitter spacetime in spherical coordinates, we subsequently stipulate the falloffs of the null tetrad and spin coefficients for asymptotically de Sitter spacetimes such that the terms which would give rise to the Bondi mass-loss due to energy carried by gravitational radiation (i.e., involving ${\sigma }^o$) must be nonzero. After solving the vacuum Newman-Penrose equations asymptotically, we propose a generalization to the Bondi mass involving $\mathrm{\Lambda }$ and obtain a positive-definite mass-loss formula by integrating the Bianchi identity involving $D^{\prime }{\mathrm{\Psi }}_2$ over a compact 2-surface on $\mathcal{I}$. Whilst our original intention was to study asymptotically de Sitter spacetimes, the use of spherical coordinates implies that this readily applies for $\mathrm{\Lambda }<0$, and yields exactly the known asymptotically flat spacetimes when $\mathrm{\Lambda }=0$. In other words, our asymptotic vacuum solutions with $\mathrm{\Lambda }\ne 0$ reduce smoothly to those where $\mathrm{\Lambda }=0$, in spite of the distinct characters of $\mathcal{I}$ being spacelike, timelike, and null for de Sitter, anti-de Sitter, and Minkowski, respectively. Unlike for $\mathrm{\Lambda }=0$ where no incoming radiation corresponds to setting ${\mathrm{\Psi }}_0^o=0$ on some initial null hypersurface, for $\mathrm{\Lambda }\ne 0$, no incoming radiation requires ${\mathrm{\Psi }}_0^o=0$ everywhere.

We investigate a way of imposing simplicity constraints in a holomorphic spin foam model that we recently introduced. Rather than imposing the constraints on the boundary spin network, as is usually done, one can impose the constraints directly on the spin foam propagator. We find that the two approaches have the same leading asymptotic behavior, with differences appearing at higher order. This allows us to obtain a model that greatly simplifies calculations, but still has Regge calculus as its semiclassical limit.

Black holes that have nearly evaporated are often thought of as small objects, due to their tiny exterior area. However, the horizon bounds large spacelike hypersurfaces. A compelling geometric perspective on the evolution of the interior geometry was recently shown to be provided by a generally covariant definition of the volume inside a black hole using maximal surfaces. In this article, we expand on previous results and show that finding the maximal surfaces in an arbitrary spherically symmetric spacetime is equivalent to a $1+1$ geodesic problem. We then study the effect of Hawking radiation on the volume by computing the volume of maximal surfaces inside the apparent horizon of an evaporating black hole as a function of time at infinity: while the area is shrinking, the volume of these surfaces grows monotonically with advanced time, up to when the horizon has reached Planckian dimensions. The physical relevance of these results for the information paradox and the remnant scenarios are discussed.

Unprecedentedly precise cosmic microwave background (CMB) data are expected from ongoing and near-future CMB stage III and IV surveys, which will yield reconstructed CMB lensing maps with effective resolution approaching several arcminutes. The small-scale CMB lensing fluctuations receive non-negligible contributions from nonlinear structure in the late-time density field. These fluctuations are not fully characterized by traditional two-point statistics, such as the power spectrum. Here, we use $N$-body ray-tracing simulations of CMB lensing maps to examine two higher-order statistics: the lensing convergence one-point probability distribution function (PDF) and peak counts. We show that these statistics contain significant information not captured by the two-point function and provide specific forecasts for the ongoing stage III Advanced Atacama Cosmology Telescope (AdvACT) experiment. Considering only the temperature-based reconstruction estimator, we forecast $9\sigma$ (PDF) and $6\sigma$ (peaks) detections of these statistics with AdvACT. Our simulation pipeline fully accounts for the non-Gaussianity of the lensing reconstruction noise, which is significant and cannot be neglected. Combining the power spectrum, PDF, and peak counts for AdvACT will tighten cosmological constraints in the ${\mathrm{\Omega }}_m\text{−}{\sigma }_8$ plane by $\approx 30\%$, compared to using the power spectrum alone.

We consider the low scale implications in the ${\mathrm{U}(1)}^{\prime }$ extended minimal supersymmetric Standard Model (UMSSM). We restrict the parameter space such that the lightest supersymmetric particle (LSP) is always the lightest neutralino. In addition, we impose quasi-Yukawa unification (QYU) at the grand unification scale ($M_{\mathrm{GUT}}$). QYU strictly requires the ratios among the Yukawa couplings as $y_t/y_b\sim 1.2$, $y_{\tau }/y_b\sim 1.4$, and $y_t/y_{\tau }\sim 0.8$. We find that the need for fine-tuning over the fundamental parameter space of QYU is in the acceptable range (${\mathrm{\Delta }}_{\mathrm{EW}}\le 10^3$), even if the universal boundary conditions are imposed at $M_{\mathrm{GUT}}$, in contrast to CMSSM and nonuniversal Higgs masses. The UMSSM with universal boundary conditions yields heavy stops ($m_{\tilde{t}}\gtrsim 2.5\mathrm{TeV}$), gluinos ($m_{\tilde{g}}\gtrsim 2\mathrm{TeV}$), and squarks from the first two families ($m_{\tilde{q}}\gtrsim 4\mathrm{TeV}$). Similarly, the stau mass is bounded from below at about 1.5 TeV. Despite this heavy spectrum, we find ${\mathrm{\Delta }}_{\mathrm{EW}}\gtrsim 300$, which is much lower than that needed for the minimal supersymmetric models. In addition, the UMSSM yields a relatively small $\mu$ term, and the LSP neutralino is mostly formed by the Higgsinos of mass $\gtrsim 700\mathrm{GeV}$. We also obtain bino-like dark matter of mass about 400 GeV. The wino is usually found to be heavier than Higgsinos and binos, but there is a small region where $\mu \sim M_1\sim M_2\sim 1\mathrm{TeV}$. We also identify a chargino-neutralino coannihilation channel and $A$-resonance solutions which reduce the relic abundance of LSP neutralinos down to the ranges compatible with the current WMAP and Planck measurements.