The simple assumption of an instantaneous reionization of the Universe may bias estimates of cosmological parameters. In this paper a model-independent principal component method for the reionization history is applied to give constraints on the cosmological parameters from recent Planck 2015 data. We find that the Universe is not completely reionized at redshifts $z\ge 8.5$ at 95% C.L. Both the reionization optical depth and matter fluctuation amplitude are higher than but consistent with those obtained in the standard instantaneous reionization scheme. The high estimated value of the matter fluctuation amplitude strengthens the tension between Planck cosmic microwave background observations and some astrophysical data, such as cluster counts and weak lensing. The tension can be significantly relieved if the neutrino masses are allowed to vary. Thanks to a high scalar spectral index, the low-scale spontaneously broken supersymmetry inflationary model can fit the data well, which is marginally disfavored at 95% C.L. in the Planck analysis.

We test the plausibility of the hypothesis that the annihilation of a Majorana fermion dark matter particle via a scalar mediator explains the gamma ray excess from the Galactic center. Assuming that the mediator couples to all third generation fermions we calculate observables for dark matter abundance and scattering on nuclei, gamma, positron, and antiproton cosmic ray fluxes, radio emission from dark matter annihilation, and the effect of dark matter annihilations on the CMB. After discarding the controversial radio observation, we show that the dark matter model simultaneously fits the observed excesses in the cosmic gamma ray, the positron, and antiproton fluxes, while evading constraints from the CMB and direct detection. The experimental data are consistent with a dark matter (mediator) mass in the 10–100 (3–1000) GeV region and with weakly correlated couplings to bottom quarks and tau leptons with values of ${10}^{-3}-1$ at the 68% credibility level.

The power spectrum of the cosmic microwave background from both the Planck and WMAP data exhibits a slight dip for multipoles in the range of $l=10–30$. We show that such a dip could be the result of the resonant creation of massive particles that couple to the inflaton field. For our best-fit models, the epoch of resonant particle creation reenters the horizon at a wave number of $k_{*}\sim 0.00011\pm 0.0004$ ($h{\mathrm{Mpc}}^{-1}$). The amplitude and location of this feature corresponds to the creation of a number of degenerate fermion species of mass $\sim (8–11)/{\lambda }^{3/2}$ $m_{pl}$ during inflation where $\lambda \sim (1.0\pm 0.5)N^{-2/5}$ is the coupling constant between the inflaton field and the created fermion species, while $N$ is the number of degenerate species. Although the evidence is of marginal statistical significance, this could constitute new observational hints of unexplored physics beyond the Planck scale.

We study dark matter (DM) production in the mono-$Z$ channel at the 13 TeV LHC both in an effective field theory framework and in simplified models with vector mediators, using a multivariate analysis. For DM-quark effective operators with scalar, vector, and tensor couplings and DM mass of 100 GeV, the $5\sigma$ reach in the DM interaction scale $\mathrm{\Lambda }$ is around 2, 1, and 3 TeV, respectively, for $3{\mathrm{ab}}^{-1}$ and assuming a 5% systematic uncertainty on the total background normalization. For simplified models with leptophobic vector mediators, the $5\sigma$ reach for the mass of the mediator is 1.7 TeV also assuming a 5% systematics and $3{\mathrm{ab}}^{-1}$ of integrated luminosity. The reach for the dark matter interaction scale obtained with the multivariate analysis using a likelihood function discriminant is at least twice as high as that obtained from a simple cut and count analysis, once systematics on the background normalization larger than a few percent are taken into account. Moreover, the reach is much more stable against degradation due to these systematic uncertainties.

In this article we complete our formalism relating the finite-volume energy spectrum of a scalar quantum field theory to the three-to-three scattering amplitude, ${\mathcal{M}}_3$. In previous work [Phys. Rev. D 90, 116003 (2014)], we found a quantization condition relating the spectrum to a nonstandard infinite-volume quantity, denoted ${\mathcal{K}}_{\mathrm{df},3}$. Here we present the relation between ${\mathcal{K}}_{\mathrm{df},3}$ and ${\mathcal{M}}_3$. We then discuss briefly how our now completed formalism can be practically implemented to extract ${\mathcal{M}}_3$ from the finite-volume energy spectrum.

The two-dimensional U(1) gauge-Higgs model with a topological term is a simple example of a lattice field theory where the complex action problem comes from the topological term. We show that the model can be exactly rewritten in terms of dual variables, such that the dual partition sum has only real and positive contributions. Using suitable algorithms the dual formulation allows for Monte Carlo simulations at arbitrary values of the vacuum angle. We demonstrate the feasibility of the dual simulation and study the continuum limit, as well as the phase diagram of the system.

We investigate Yang-Lee zeros of grand partition functions as truncated fugacity polynomials of which coefficients are given by the canonical partition functions $Z(T,V,N)$ up to $N\le N_{\max }$. Such a partition function can be inevitably obtained from the net-baryon number multiplicity distribution in relativistic heavy ion collisions, where the number of the event beyond $N_{\max }$ has insufficient statistics, as well as from canonical approaches in lattice QCD. We use a chiral random matrix model as a solvable model for chiral phase transition in QCD and show that the closest edge of the distribution to the real chemical potential axis is stable against cutting the tail of the multiplicity distribution. A similar behavior is also found in lattice QCD at finite temperature for the Roberge-Weiss transition. In contrast, such a stability is found to be absent in the Skellam distribution which does not have a phase transition. We compare the number of $N_{\max }$ to obtain the stable Yang-Lee zeros with those of critical higher-order cumulants.

We give simple arguments for new nonrenormalization theorems on higher derivative couplings of gauge theories to supergravity, with sixteen supersymmetries, by considerations of brane-bulk superamplitudes. This leads to some exact results on the effective coupling of D3-branes in type IIB string theory. We also derive exact results on higher dimensional operators in the torus compactification of the six dimensional (0,2) superconformal theory.

In a Lorentz- and $CPT$-violating modification of electrodynamics that includes a timelike Chern-Simons term, there are no energy losses through vacuum Cerenkov radiation. A charge moving with a constant velocity does not lose energy, because of an unusual cancellation. Higher frequency modes of the electromagnetic field carry away positive energy, but lower frequency modes carry away a compensating negative amount of energy.

Boundary effects produced by a Chern-Simons (CS) extension to electrodynamics are analyzed exploiting the Green’s function (GF) method. We consider the electromagnetic field coupled to a $\theta$ term in a way that has been proposed to provide the correct low-energy effective action for topological insulators (TI). We take the $\theta$ term to be piecewise constant in different regions of space separated by a common interface $\mathrm{\Sigma }$, which will be called the $\theta$ boundary. Features arising due to the presence of the boundary, such as magnetoelectric effects, are already known in CS extended electrodynamics, and solutions for some experimental setups have been found, each with its specific configuration of sources. In this work we illustrate a method to construct the GF that allows us to solve the CS modified field equations for a given $\theta$ boundary with otherwise arbitrary configuration of sources. The method is illustrated by solving the case of a planar $\theta$ boundary but can also be applied for cylindrical and spherical geometries for which the $\theta$ boundary can be characterized by a surface where a given coordinate remains constant. The static fields of a pointlike charge interacting with a planar TI, as described by a planar discontinuity in $\theta$, are calculated and successfully compared with previously reported results. We also compute the force between the charge and the $\theta$ boundary by two different methods, using the energy-momentum tensor approach and the interaction energy calculated via the GF. The infinitely straight current-carrying wire is also analyzed.

The equivalence of cooling to the gradient flow when the cooling step $n_c$ and the continuous flow step of gradient flow $\tau$ are matched is generalized to gauge actions that include rectangular terms. By expanding the link variables up to subleading terms in perturbation theory, we relate $n_c$ and $\tau$ and show that the results for the topological charge become equivalent when rescaling $\tau \simeq n_c/(3-15c_1)$, where $c_1$ is the Symanzik coefficient multiplying the rectangular term. We, subsequently, apply cooling and the gradient flow using the Wilson, the Symanzik tree-level improved, and the Iwasaki gauge actions to configurations produced with $N_f=2+1+1$ twisted mass fermions. We compute the topological charge, its distribution, and the correlators between cooling and gradient flow at three values of the lattice spacing demonstrating that the perturbative rescaling $\tau \simeq n_c/(3-15c_1)$ leads to equivalent results.

We use the recently derived density of states for a particle confined to a spherical well in three-dimensional fuzzy space to compute the thermodynamics of a gas of noninteracting fermions confined to such a well. Special emphasis is placed on noncommutative effects, and in particular, noncommutative corrections to the thermodynamics at low densities and temperatures are computed where the nonrelativistic approximation used here is valid. Noncommutative effects at high densities are also identified, the most prominent being the existence of a minimal volume at which the gas becomes incompressible. The latter is closely related to a low/high-density duality exhibited by these systems, which in turn is a manifestation of an infrared/ultraviolet duality in the single-particle spectrum. Both nonrotating and slowly rotating gasses are studied. Approximations are benchmarked against exact numerical computations for the nonrotating case, and several other properties of the gas are demonstrated with numerical computations. Finally, a noncommutative gas confined by gravity is studied, and several novel features regarding the mass-radius relation, density and entropy are highlighted.

The second order hydrodynamical description of a homogeneous conformal plasma that undergoes a boost-invariant expansion is given by a single nonlinear ordinary differential equation, whose resurgent asymptotic properties we study, developing further the recent work of Heller and Spalinski [Phys. Rev. Lett. 115, 072501 (2015)]. Resurgence clearly identifies the nonhydrodynamic modes that are exponentially suppressed at late times, analogous to the quasinormal modes in gravitational language, organizing these modes in terms of a trans-series expansion. These modes are analogs of instantons in semiclassical expansions, where the damping rate plays the role of the instanton action. We show that this system displays the generic features of resurgence, with explicit quantitative relations between the fluctuations about different orders of these nonhydrodynamic modes. The imaginary part of the trans-series parameter is identified with the Stokes constant, and the real part with the freedom associated with initial conditions.

We have shown coherent state quantization of a particle in a maximally symmetric curved space-time i.e. in de Sitter space. As the coherent states are eigenvectors of the lowering operators, we have constructed the raising and lowering operators with the help of recurrence relation satisfied by the associated Legendre polynomial. These lowering operators have been used to describe an explicit form of coherent states followed by coherent states quantization in two-dimensional de Sitter space. Coherent states and their quantization are also generalized in D-dimensional de Sitter space.

In the context of the geometrical interpretation of the spin network states of loop quantum gravity, we look at the holonomies of the Ashtekar-Barbero connection on loops embedded in spacelike hyperboloids. We use this simple setting to illustrate two points. First, the Ashtekar-Barbero connection is not a space-time connection, its holonomies depend on the space-time embedding of the canonical hypersurface. This fact is usually interpreted as an inconvenience, but we use it to extract the extrinsic curvature from the holonomy and separate it from the 3d intrinsic curvature. Second, we show the limitations of this reconstruction procedure, due to a periodicity of the holonomy in the Immirzi parameter, which underlines the role of a real Immirzi parameter as a cutoff for general relativity at the quantum level in contrast with its role of a mere coupling constant at the classical level.

The multipole moments and the tidal Love numbers of neutron stars and quark stars satisfy certain relations which are almost insensitive to the star’s internal structure. A natural question is whether the same relations hold for different compact objects and how they possibly approach the black-hole limit. Here we consider “gravastars,” which are hypothetical compact objects sustained by their internal vacuum energy. Such solutions have been proposed as exotic alternatives to the black-hole paradigm because they can be as compact as black holes and exist in any mass range. By constructing slowly rotating, thin-shell gravastars to quadratic order in the spin, we compute the moment of inertia $I$, the mass quadrupole moment $Q$, and the tidal Love number $\lambda$ in exact form. The $I-\lambda -Q$ relations of a gravastar are dramatically different from those of an ordinary compact star, but the black-hole limit is continuous; i.e., these quantities approach their Kerr counterparts when the compactness is maximum. Therefore, such relations can be used to discern a gravastar from an ordinary compact star but not to break the degeneracy with the black-hole case. Based on these results, we conjecture that the full multipolar structure and the tidal deformability of a spinning, ultracompact gravastar are identical to those of a Kerr black hole. The approach to the black-hole limit is nonpolynomial, thus differing from the critical behavior recently found for strongly anisotropic neutron stars.

The quantization of the Hamiltonian for a scalar field is performed in the framework of quantum reduced loop gravity. We outline how the regularization can be performed by using the analogous tools adopted in full loop quantum gravity, and the matrix elements of the resulting operator between basis states are analytic coefficients. These achievements open the way for a consistent analysis of the quantum gravity corrections to the classical dynamics of gravity in the presence of a scalar field in a cosmological setting.

The initial conditions for Newtonian $N$-body simulations are usually generated by applying the Zel’dovich approximation to the initial displacements of the particles using an initial power spectrum of density fluctuations generated by an Einstein-Boltzmann solver. We show that in most gauges the initial displacements generated in this way receive a first-order relativistic correction. We define a new gauge, the $N$-body gauge, in which this relativistic correction vanishes and show that a conventional Newtonian $N$-body simulation includes all first-order relativistic contributions (in the absence of radiation) if we identify the coordinates in Newtonian simulations with those in the relativistic $N$-body gauge.

Using a discrete flavor group, $A_5$, combined with generalized $CP$, we study the mixing parameter correlations which arise from breaking to residual symmetries in the neutrino $G_{\nu }={\mathbb{Z}}_2\times CP$, and the charged lepton sectors $G_e={\mathbb{Z}}_2$. By focusing on patterns that agree with current experimental data we demonstrate that nontrivial leptonic phases are predicted and discuss a number of distinctive correlations between mixing parameters.