We propose an ansatz which solves the Dyson-Schwinger equation for the real scalar fields in a Poincaré patch of de Sitter space in the infrared limit. The Dyson-Schwinger equation for this ansatz reduces to the kinetic equation, if one considers scalar fields from the principal series. Solving the latter equation we show that under the adiabatic switching on and then off of the coupling constant, the Bunch-Davies vacuum relaxes in future infinity to the state with the flat Gibbons-Hawking density of out-Jost harmonics on top of the corresponding de Sitter invariant out vacuum.

We compare dynamics and waveforms from binary neutron star coalescence as computed by new long-term ($\sim 10$ orbits) numerical relativity simulations and by the tidal effective-one-body (EOB) model including analytical tidal corrections up to second post-Newtonian order. The current analytic knowledge encoded in the tidal EOB model is found to be sufficient to reproduce the numerical data up to contact and within their uncertainties. Remarkably, no calibration of any tidal EOB free parameters is required, beside those already fitted to binary black holes data. The inclusion of second post-Newtonian order tidal corrections minimizes the differences with the numerical data, but it is not possible to significantly distinguish them from the leading-order tidal contribution. The presence of a relevant amplification of tidal effects is likely to be excluded, although it can appear as a consequence of numerical inaccuracies. We conclude that the tidally completed effective-one-body model provides nowadays the most advanced and accurate tool for modeling gravitational waveforms from binary neutron star inspiral up to contact. This work also points out the importance of extensive tests to assess the uncertainties of the numerical data and the potential need of new numerical strategies to perform accurate simulations.

We derive the radiation reaction forces on a compact binary inspiral through 3.5 order in the post-Newtonian expansion using the effective field theory approach. We utilize a recent formulation of Hamilton’s variational principle that rigorously extends the usual Lagrangian and Hamiltonian formalisms to dissipative systems, including the inspiral of a compact binary from the emission of gravitational waves. We find agreement with previous results, which thus provides a non-trivial confirmation of the extended variational principle. The results from this work nearly complete the equations of motion for the generic inspiral of a compact binary with spinning constituents through 3.5 post-Newtonian order, as derived entirely with effective field theory, with only the spin-orbit corrections to the potential at 3.5 post-Newtonian remaining.

Stellar collapse and the subsequent development of a core-collapse supernova explosion emit bursts of gravitational waves (GWs) that might be detected by the advanced generation of laser interferometer gravitational-wave observatories such as Advanced LIGO, Advanced Virgo, and LCGT. GW bursts from core-collapse supernovae encode information on the intricate multidimensional dynamics at work at the core of a dying massive star and may provide direct evidence for the yet uncertain mechanism driving supernovae in massive stars. Recent multidimensional simulations of core-collapse supernovae exploding via the neutrino, magnetorotational, and acoustic explosion mechanisms have predicted GW signals which have distinct structure in both the time and frequency domains. Motivated by this, we describe a promising method for determining the most likely explosion mechanism underlying a hypothetical GW signal, based on principal component analysis and Bayesian model selection. Using simulated Advanced LIGO noise and assuming a single detector and linear waveform polarization for simplicity, we demonstrate that our method can distinguish magnetorotational explosions throughout the Milky Way ($D\lesssim 10\mathrm{kpc}$) and explosions driven by the neutrino and acoustic mechanisms to $D\lesssim 2\mathrm{kpc}$. Furthermore, we show that we can differentiate between models for rotating accretion-induced collapse of massive white dwarfs and models of rotating iron core collapse with high reliability out to several kpc.

We describe inhomogeneities in a $\Lambda \mathrm{CDM}$ universe with a gradient series expansion and show that it describes the gravitational evolution far into the nonlinear regime and beyond the capacity of standard perturbation theory at any order. We compare the gradient expansion with exact inhomogeneous $\Lambda \mathrm{LTB}$ solutions (Lemaître-Tolman-Bondi metric with the inclusion of a cosmological constant) describing growing structure in a $\Lambda \mathrm{CDM}$ universe and find that the expansion approximates the exact solution well, following the collapse of an over-density all the way into a singularity.

In this paper the effects of a time-dependent Newton constant $G$ during inflation are studied. We present the formalism of curvature perturbations in an inflationary system with a time-dependent Newton constant. As an example we consider a toy model in which $G$ undergoes a sudden change during inflation. By imposing the appropriate matching conditions the imprints of this sharp change in $G$ on the curvature perturbation power spectrum are studied. We show that if $G$ increases (decreases) during the transition the amplitude of curvature perturbations on large scales decreases (increases). In our model with a sudden change in $G$ continuous sinusoidal modulations on the curvature power spectrum is induced. However, in a realistic scenario in which the change in $G$ has some finite time scale we expect these sinusoidal modulations to be damped on short scales. The generated features may be used to explain the observed glitches on the CMB power spectrum. This puts a bound on $\Delta G$ during inflation of roughly the same order as current bounds on $\Delta G$ during the entire observed age of the universe.

Superconducting cosmic strings can give transient electromagnetic signatures that we argue are most evident at radio frequencies. We investigate the three different kinds of radio bursts from cusps, kinks, and kink-kink collisions on superconducting strings. We find that the event rate is dominated by kink bursts in a range of parameters that are of observational interest, and can be quite high (several a day at 1 Jy flux) for a canonical set of parameters. In the absence of events, the search for radio transients can place stringent constraints on superconducting cosmic strings.

Background: The recent disagreement between the proton charge radius extracted from Lamb shift measurements of muonic and electronic hydrogen invites speculation that new physics may be to blame. Several proposals have been made for new particles that account for both the Lamb shift and the muon anomalous moment discrepancies. Purpose: We explore the possibility that new particles’ couplings to the muon can be fine-tuned to account for all experimental constraints. Method: We consider two fine-tuned models, the first involving new particles with scalar and pseudoscalar couplings, and the second involving new particles with vector and axial couplings. The couplings are constrained by the Lamb shift and muon magnetic moment measurements while mass constraints are obtained by kaon decay rate data. Results: For the scalar-pseudoscalar model, masses between 100 to 200 MeV are not allowed. For the vector model, masses below about 200 MeV are not allowed. The strength of the couplings for both models approach that of electrodynamics for particle masses of about 2 GeV. Conclusions: New physics with fine-tuned couplings may be entertained as a possible explanation for the Lamb shift discrepancy.

We report on a study of diffractive dijet production in $\overline{p}p$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$ using the CDF II detector at the Fermilab Tevatron $\overline{p}p$ collider. A data sample from $310{\mathrm{pb}}^{-1}$ of integrated luminosity collected by triggering on a high transverse energy jet, $E_T^{\mathrm{jet}}$, in coincidence with a recoil antiproton detected in a Roman pot spectrometer is used to measure the ratio of single-diffractive to inclusive-dijet event rates as a function of $x^{\overline{p}}$ of the interacting parton in the antiproton, the Bjorken-$x$, $x_{\mathrm{Bj}}^{\overline{p}}$, and a $Q^2\approx (E_T^{\mathrm{jet}}{)}^2$ in the ranges ${10}^{-3}<x_{\mathrm{Bj}}^{\overline{p}}<{10}^{-1}$ and ${10}^2<Q^2<{10}^4{\mathrm{GeV}}^2$, respectively. Results are presented for the region of $\overline{p}$-momentum-loss fraction $0.03<{\xi }_{\overline{p}}<0.09$ and a four-momentum transfer squared $t_{\overline{p}}>-4{\mathrm{GeV}}^2$. The $t_{\overline{p}}$ dependence is measured as a function of $Q^2$ and $x_{\mathrm{Bj}}^{\overline{p}}$ and compared with that of inclusive single diffraction dissociation. We find weak $x_{\mathrm{Bj}}^{\overline{p}}$ and $Q^2$ dependencies in the ratio of single diffractive to inclusive event rates, and no significant $Q^2$ dependence in the diffractive $t_{\overline{p}}$ distributions.

We show that there is no superradiance in the rotating BTZ black hole for vanishing boundary conditions at infinity for the real scalar field.

When matter falls past the horizon of a large black hole, the expectation from string theory is that the configuration thermalizes and the information in the probe is rather quickly scrambled away. The traditional view of a classical unique spacetime near a black hole horizon conflicts with this picture. The question then arises as to what spacetime does the probe actually see as it crosses a horizon, and how does the background geometry imprint its signature onto the thermal properties of the probe. In this work, we explore these questions through an extensive series of numerical simulations of D0 branes. We determine that the D0 branes quickly settle into an incompressible symmetric state—thermalized within a few oscillations through a process driven entirely by internal nonlinear dynamics. Surprisingly, thermal background fluctuations play no role in this mechanism. Signatures of the background fields in this thermal state arise either through fluxes, i.e. black hole hair; or if the probe expands to the size of the horizon—which we see evidence of. We determine simple scaling relations for the D0 branes’ equilibrium size, time to thermalize, lifetime, and temperature in terms of their number, initial energy, and the background fields. Our results are consistent with the conjecture that black holes are the fastest scramblers as seen by matrix theory.

We continue our investigation of correlation functions of the large-$N$ (planar) limit of the ($1+1$)-dimensional principal chiral sigma model, whose bare field $U(x)$ lies in the fundamental matrix representation of $\mathrm{SU}(N)$. We find all the form factors of the renormalized field $\Phi (x)$. An exact formula for Wightman and time-ordered correlation functions is found.

this paper, we study the effect of $\kappa$ deformation of the space-time on the response function of a uniformly accelerating detector coupled to a scalar field. Starting with $\kappa$-deformed Klein-Gordon theory, which is invariant under a $\kappa$-Poincaré algebra and written in commutative space-time, we derive $\kappa$-deformed Wightman functions, valid up to second order in the deformation parameter $a$. Using this, we show that the first nonvanishing correction to the Unruh thermal distribution is only in the second order in $a$. We also discuss various other possible sources of $a$-dependent corrections to this thermal distribution.

We apply the derivative expansion approach to the Casimir effect for a real scalar field in $d$ spatial dimensions to calculate the next-to-leading-order term in that expansion, namely, the first correction to the proximity force approximation. The field satisfies either Dirichlet or Neumann boundary conditions on two static mirrors, one of them flat and the other gently curved. We show that, for Dirichlet boundary conditions, the next-to-leading-order term in the Casimir energy is of quadratic order in derivatives, regardless of the number of dimensions. Therefore, it is local and determined by a single coefficient. We show that the same holds true, if $d\ne 2$, for a field which satisfies Neumann conditions. When $d=2$, the next-to-leading-order term becomes nonlocal in coordinate space, a manifestation of the existence of a gapless excitation (which does exist also for $d>2$, but produces subleading terms). We also consider a derivative expansion approach including thermal fluctuations of the scalar field. We show that, for Dirichlet mirrors, the next-to-leading-order term in the free energy is also local for any temperature $T$. Besides, it interpolates between the proper limits: when $T\to 0$, it tends to the one we had calculated for the Casimir energy in $d$ dimensions, while for $T\to \infty$, it corresponds to the one for a theory in $d-1$ dimensions, because of the expected dimensional reduction at high temperatures. For Neumann mirrors in $d=3$, we find a nonlocal next-to-leading-order term for any $T>0$.

We study the dynamical chiral symmetry breaking of three-dimensional quantum electrodynamics (${\mathrm{QED}}_3$) at finite temperature and chemical potential in the leading order of Dyson-Schwinger equation approach. After considering the chemical potential dependence of the boson propagator, we derive the expression for the boson polarization and then obtain the corresponding chiral phase diagram in the ($T\mathrm{\text{−}}\mu$) plane. A comparison between the phase diagram obtained above and the one obtained without considering the chemical potential dependence of the boson propagator is made. It is found that in a self-consistent study of the chiral phase diagram of ${\mathrm{QED}}_3$, the chemical potential dependence of the boson propagator cannot be neglected.

In this paper, we construct for the first time the noncommutative fluid with the deformed Poincaré invariance. To this end, the realization formalism of the noncommutative spaces is employed and the results are particularized to the Snyder space. The noncommutative fluid generalizes the fluid model in the action functional formulation to the noncommutative space. The fluid equations of motion and the conserved energy-momentum tensor are obtained.

We study resummed perturbative contributions due to a heavy top quark. These renormalon contributions are evaluated for fermion propagators. Results for the top-quark width are given. Estimates of nonperturbative uncertainties are made on the $\rho$ parameter using different schemes of dealing with the Landau pole. For the physical top-quark mass the effects are negligible.

We study the energy conditions and geodesic deformations in Bertrand space-times. We show that these can be thought of as interesting physical space-times in certain regions of the underlying parameter space, where the weak and strong energy conditions hold. We further compute the ESR parameters and analyze them numerically. The focusing of radial timelike and radial null geodesics is shown explicitly, which verifies the Raychaudhuri equation.

We numerically construct an one-parameter family of initial data of an expanding inhomogeneous universe model which is composed of regularly aligned black holes with an identical mass. They are initial data for vacuum solutions of the Einstein equations. We call this universe model the “black hole universe” and analyze the structure of these initial data. We study the relation between the mean expansion rate of the 3-space, which corresponds to the Hubble parameter, and the mass density of black holes. The result implies that the same relation as that of the Einstein-de Sitter universe is realized in the limit of the large separation between neighboring black holes. The applicability of the cosmological Newtonian $N$-body simulation to the dark matter composed of black holes is also discussed. The deviation of the spatial metric of the cosmological Newtonian $N$-body system from that of the black hole universe is found to be smaller than about 1% in a region distant from the particles, if the separation length between neighboring particles is 20 times larger than their gravitational radius. By contrast, the deviation of the square of the Hubble parameter of the cosmological Newtonian $N$-body system from that of the black hole universe is about 20% for the same separation length.