Vacuum polarization (or Casimir) energies can be straightforwardly computed from scattering data for static field configurations whose interactions with the fluctuating field are frequency independent. In effective theories, however, such interactions are typically frequency dependent. As a consequence, the relationship between scattering data and the Green’s function is modified, which may or may not induce additional contributions to the vacuum polarization energy. We discuss several examples that naturally include frequency dependent interactions: (i) scalar electrodynamics with a static background potential, (ii) an effective theory that emerges from integrating out a heavy degree of freedom, and (iii) quantum electrodynamics coupled to a frequency dependent dielectric material. In the latter case, we argue that introducing dissipation as required by the Kramers-Kronig relations requires the consideration of the Casimir energy within a statistical mechanics formalism, while in the absence of dissipation, we can work entirely within field theory, using an alternative formulation of the energy density.

We present a variation of earlier attempts to relate renormalization group equations to higher spin equations. We work with a scalar field theory in 3 dimensions. In this case we show that the classical renormalization group equation is a variant of the Vasiliev higher spin equations with Kleinians on ${\mathrm{AdS}}_4$ for a certain subset of couplings. In the large N limit this equivalence extends to the quantum theory away from the conformal fixed points.

We examine an exact solution which represents a charged black hole in a Kaluza-Klein universe in the five-dimensional Einstein-Maxwell theory. The spacetime approaches to the five-dimensional Kasner solution that describes a universe with the expanding three-dimensional space and the shrinking extra dimension in the far region. The metric is continuous but not smooth at the black hole horizon. There appears a mild curvature singularity that a free-fall observer can traverse the horizon. The horizon is a squashed three-sphere with a constant size, and the metric is approximately static near the horizon.

We compute the evolution of cosmological perturbations in a recently proposed Weyl-symmetric theory of two scalar fields with oppositely signed conformal couplings to Einstein gravity. It is motivated from the minimal conformal extension of the standard model, such that one of these scalar fields is the Higgs while the other is a new particle, the dilaton, introduced to make the Higgs mass conformally symmetric. At the background level, the theory admits novel geodesically complete cyclic cosmological solutions characterized by a brief period of repulsive gravity, or “antigravity,” during each successive transition from a big crunch to a big bang. For simplicity, we consider scalar perturbations in the absence of anisotropies, with potential set to zero and without any radiation. We show that despite the necessarily wrong-signed kinetic term of the dilaton in the full action, these perturbations are neither ghostlike nor tachyonic in the limit of strongly repulsive gravity. On this basis, we argue—pending a future analysis of vector and tensor perturbations—that, with respect to perturbative stability, the cosmological solutions of this theory are viable.

We study the effects of primordial magnetic fields on the inflationary potential in the context of a warm inflation scenario. The model, based on global supersymmetry with a new-inflation-type potential and a coupling between the inflaton and a heavy intermediate superfield, is already known to preserve the flatness required for slow-roll conditions even after including thermal contributions. Here we show that the magnetic field makes the potential even flatter, retarding the transition and rendering it smoother.

We study the impact of higher-order quark-meson scattering processes on the chiral phase structure of two-flavor QCD at finite temperature and quark density. Thermal, density and quantum fluctuations are included within a functional renormalization group approach to the quark-meson model. We present results on the chiral phase boundary, the critical endpoint, and the curvature of the phase transition line at vanishing density.

In this paper, we firstly verify that the factorization hypothesis is valid for the exclusive process $\rho {\gamma }^{\star }\to \pi$ at the next-to-leading order (NLO) with the collinear factorization approach, and then extend this proof to the case of the $k_T$ factorization approach. We particularly show that at the NLO level, the soft divergences in the full quark level calculation could be canceled completely as for the $\pi {\gamma }^{\star }\to \pi$ process where only the pseudoscalar $\pi$ meson is involved, and the remaining collinear divergences can be absorbed into the NLO hadron wave functions. The full amplitudes can be factorized as the convolution of the NLO wave functions and the infrared-finite hard kernels with these factorization approaches. We also write out the NLO meson distribution amplitudes in the form of nonlocal matrix elements.

Supersymmetry is under pressure from LHC searches requiring colored superpartners to be heavy. We demonstrate $R$-parity violating (RPV) spectra for which the dominant signatures are not currently well searched for at the LHC. In such cases, the bounds can be as low as 800 GeV on both squarks and gluinos. We demonstrate that there are nontrivial constraints on squark and gluino masses with baryonic RPV ($UDD$ operators) and show that in fact leptonic RPV can allow comparable or even lighter superpartners. The constraints from many searches are weakened if the LSP is significantly lighter than the colored superpartners, such that it is produced with high boost. The LSP decay products will then be collimated, leading to the miscounting of leptons or jets and causing such models to be missed even with large production cross-sections. Other leptonic RPV scenarios that evade current searches include the highly motivated case of a Higgsino LSP decaying to a tau and two quarks, and the case of a long-lived LSP with a displaced decay to electrons and jets. The least constrained models can have SUSY production cross-sections of $\sim \mathrm{pb}$ or larger, implying tens of thousands of SUSY events in the 8 TeV data. We suggest novel searches for these signatures of RPV, which would also improve the search for general new physics at the LHC.

We explore the phenomenological implications on nonminimal flavor violating (NMFV) processes from squark flavor mixing within the minimal supersymmetric standard model (MSSM). We work under the model-independent hypothesis of general flavor mixing in the squark sector, being parametrized by a complete set of dimensionless ${\delta }_{ij}^{AB}$ ($A,B=L,R$; $i,j=u,c,t$ or $d,s,b$; $i\ne j$) parameters. The present upper bounds on the most relevant NMFV processes, together with the requirement of compatibility in the choice of the MSSM parameters with the recent LHC and $(g-2{)}_{\mu }$ data, lead to updated constraints on all squark flavor mixing parameters.

We consider a recently proposed model that posits the existence of composite dark matter, wherein dark “quarks” transforming as fundamentals under an $SU(3{)}_d$ gauge group undergo a confining phase and form dark baryons. The model attempts to explain both the $\mathcal{O}(1)$ relic density ratio, ${\mathrm{\Omega }}_{\text{dark}}/{\mathrm{\Omega }}_{\text{baryon}}\sim 5.4$, as well as the asymmetric production of both dark and baryonic matter via leptogenesis. Though the solution of $\beta$ functions for $SU(3{)}_c$ and $SU(3{)}_d$ constitutes the main drive of the model, no threshold corrections were taken into account as the renormalization scale crosses the mass threshold of the heavy new fields in the model. We extend this work by explicitly calculating the threshold-corrected renormalization-group flow for the theory using an effective-field matching technique. We find that the theory has a much wider range of applicability than previously thought and that a significant fraction of models (defined by the number of fields contained therein) is able to account for the observed relic density.

The analysis of current ultrahigh energy data for hadronic total cross sections and diffractive scattering cross sections points to a steady growth of the optical density with energy for elastic scattering amplitudes in the impact parameter space, $b$. At LHC energy the profile function of the $pp$-scattering amplitude, $T(b)$, reaches the black disk limit at small $b$. Two scenarios are possible at larger energies, $\sqrt{s}\gtrsim 100\mathrm{TeV}$. First, the profile function gets frozen in the black disk limit, $T(b)\simeq 1$, while the radius of the black disk $R_{\text{black disk}}$ is increasing with $\ln s$, providing ${\sigma }_{\text{tot}}\sim {\ln }^{2}s$, ${\sigma }_{\text{el}}\sim {\ln }^{2}s$, ${\sigma }_{\text{inel}}\sim {\ln }^{2}s$. In another scenario the profile function continues to grow at $\sqrt{s}\gtrsim 100\mathrm{TeV}$ approaching the maximal value, $T(b)\simeq 2$, that means the resonant disk mode. We discuss features of the resonant disk mode when the disk radius, $R_{\text{resonant}\text{disk}}$, increases providing the growth of the total and elastic cross sections ${\sigma }_{\text{tot}}\sim {\ln }^{2}s$, ${\sigma }_{\text{el}}\sim {\ln }^{2}s$, but a more slow increase of inelastic cross section, ${\sigma }_{\text{inel}}\sim \ln s$.

A new measurement of the ${\theta }_{13}$ mixing angle has been obtained at the Daya Bay Reactor Neutrino Experiment via the detection of inverse beta decays tagged by neutron capture on hydrogen. The antineutrino events for hydrogen capture are distinct from those for gadolinium capture with largely different systematic uncertainties, allowing a determination independent of the gadolinium-capture result and an improvement on the precision of the ${\theta }_{13}$ measurement. With a 217-day antineutrino data set obtained with six antineutrino detectors and from six $2.9{\mathrm{GW}}_{\text{th}}$ reactors, the rate deficit observed at the far hall is interpreted as ${\sin }^{2}2{\theta }_{13}=0.083\pm 0.018$ in the three-flavor oscillation model. When combined with the gadolinium-capture result from Daya Bay, we obtain ${\sin }^{2}2{\theta }_{13}=0.089\pm 0.008$ as the final result for the six-antineutrino-detector configuration of the Daya Bay experiment.

In this note, I show that the recently proposed subleading soft factor in massless gauge theory uniquely follows from conformal symmetry of tree-level gauge theory amplitudes in four dimensions.

The melting of a heavy quark-antiquark bound state depends on the screening phenomena associated with the binding energy, as well as scattering phenomena associated with the imaginary part of the potential. We study the imaginary part of the static potential of heavy quarkonia moving in the strongly coupled plasma. The imaginary potential dependence on the velocity of the traveling bound states is calculated. Nonzero velocity leads to an increase of the absolute value of the imaginary potential. The enhancement is stronger when the quarkonia move orthogonal to the quark-gluon plasma maximizing the flux between the pair. Moreover, we estimate the thermal width of the moving bound state and find it enhanced compared to the static one. Our results imply that the moving quarkonia dissociate easier than the static ones in agreement with the expectations.

Exact analytic solutions of the Skyrme model defined on a spherically symmetric $R^{(1,1)}\times S^2$ geometry, chosen to mimic finite volume effects, are presented. The static and spherically symmetric configurations have nontrivial winding number and finite soliton mass. These configurations possess an extra topological charge, allowing for a novel BPS bound which can be saturated, unlike what happens in the standard case. Such solutions include exact multi-Skyrmions of arbitrary winding number, composed by interacting elementary Skyrmions. The values of the coupling constants and the compression modulus are found in good agreement with experiments by fitting the masses $M_N$ and $M_{\mathrm{\Delta }}$.

The quark-meson model is investigated for the two- and three-flavor case extended by contributions of vector mesons under conditions encountered in core-collapse supernova matter. Typical temperature ranges, densities, and electron fractions, as found in core-collapse supernova simulations, are studied by implementing charge neutrality and local $\beta$ equilibrium with respect to weak interactions. Within this framework, we analyze the resulting phase diagram and equation of state (EoS) and investigate the impact of undetermined parameters of the model. The EoS turns out to be relatively independent on the entropy per baryon but there are significant changes when going from the two-flavor to the three-flavor case due to the nontrivial contribution from the strange quarks which stay massive even at high densities. While an increasing vector meson coupling constant leads to a substantial stiffening of the EoS, we find that the impact of changing the scalar meson mass is equally strong and results in a softening of the EoS for increasing values.

Cosmological perturbations of Friedmann-Robertson-Walker solutions in ghost free massive bigravity, including also a second matter sector, are studied in detail. At early time, we find that subhorizon exponential instabilities are unavoidable and they lead to a premature departure from the perturbative regime of cosmological perturbations.

Phase transitions for rotating asymptotically anti–de Sitter black holes in four dimensions are described in the $P-T$ plane, in terms of the Hawking temperature and the pressure provided by the cosmological constant. The difference between constant angular momentum and constant angular velocity is highlighted; the former has a second order phase transition while the latter does not. If the angular momentum is fixed there a line of first order phase transitions terminating at a critical point with a second order phase transition and vanishing latent heat, while if the angular velocity is fixed there is a line of first order phase transitions terminating at a critical point with infinite latent heat. For constant angular velocity the analytic form of the phase boundary is determined, latent heats derived and the Clapeyron equation verified.