Constraints on the main cosmological parameters using cosmic microwave background (CMB) or large scale structure data are usually based on the power-law assumption of the primordial power spectrum (PPS). However, in the absence of a preferred model for the early Universe, this raises a concern that current cosmological parameter estimates are strongly prejudiced by the assumed power-law form of PPS. In this paper, for the first time, we perform cosmological parameter estimation allowing the free form of the primordial spectrum. This is in fact the most general approach to estimate cosmological parameters without assuming any particular form for the primordial spectrum. We use a direct reconstruction of the PPS for any point in the cosmological parameter space using the recently modified Richardson-Lucy algorithm; however, other alternative reconstruction methods could be used for this purpose as well. We use WMAP 9 year data in our analysis considering the CMB lensing effect, and we report, for the first time, that the flat spatial universe with no cosmological constant is ruled out by more than a $4\sigma$ confidence limit without assuming any particular form of the primordial spectrum. This would be probably the most robust indication for dark energy using CMB data alone. Our results on the estimated cosmological parameters show that higher values of the baryonic and matter density and a lower value of the Hubble parameter (in comparison to the estimated values by assuming power-law PPS) is preferred by the data. However, the estimated cosmological parameters by assuming a free form of the PPS have an overlap at $1\sigma$ confidence level with the estimated values assuming the power-law form of PPS.

TeV blazars offer an exciting prospect for discovering cosmological magnetic fields and for probing high-energy processes, including $CP$ violation, in the early Universe. We propose a method for reconstructing both the nonhelical and the helical magnetic field correlators using observations of cascade photons from TeV blazars.

In the standard cosmological framework, the Hubble diagram is interpreted by assuming that the light emitted by standard candles propagates in a spatially homogeneous and isotropic spacetime. However, the light from “point sources”—such as supernovae—probes the Universe on scales where the homogeneity principle is no longer valid. Inhomogeneities are expected to induce a bias and a dispersion of the Hubble diagram. This is investigated by considering a Swiss-cheese cosmological model, which (1) is an exact solution of the Einstein field equations, (2) is strongly inhomogeneous on small scales, but (3) has the same expansion history as a strictly homogeneous and isotropic universe. By simulating Hubble diagrams in such models, we quantify the influence of inhomogeneities on the measurement of the cosmological parameters. Though significant in general, the effects reduce drastically for a universe dominated by the cosmological constant.

We describe the irrotational dust component of the Universe in terms of a relativistic gradient expansion and transform the resulting synchronous metric to a Newtonian coordinate system. The two metrics are connected via a spacelike displacement field and a timelike perturbation, providing a relativistic generalization of the transformation from Lagrangian to Eulerian coordinates. The relativistic part of the displacement field generates already at initial time a nonlocal density perturbation at second order. This is a purely relativistic effect since it originates from space-time mixing. We give two options, the passive and the active approach, on how to include the relativistic corrections for example in $N$-body simulations. In the passive approach we treat the corrections as a non-Gaussian modification of the initial Gaussian field (primordial non-Gaussianity could be incorporated as well). The induced non-Gaussianity depends on scale and the redshift at which initial conditions are set, with $f_{\mathrm{NL}}\sim \mathrm{\text{few}}$ for small enough scales and redshifts. In the active approach we show how to use the relativistic trajectory to obtain the initial displacement and velocity of particles for $N$-body simulations without modifying the initial Gaussian field.

We consider the propagation and energy losses of protons and antiprotons produced by dark matter annihilation at redshifts $100<z\lesssim 2000$. In the case of dark matter annihilations into quarks, gluons and weak gauge bosons, protons and antiprotons carry about 20% of the energy injected into $e^{\pm }$ and $\gamma$’s, but their interactions are normally neglected when deriving cosmic microwave background bounds from altered recombination histories. Here, we follow numerically the energy-loss history of typical protons/antiprotons in the cosmological medium. We show that about half of their energy is channeled into photons and $e^{\pm }$, and we present a simple prescription to estimate the corresponding strengthening of the cosmic microwave background bounds on the dark matter annihilation cross section.

While the possible roles of gamma ray bursts’ (GRBs) progenitors as gravitational waves (GW) sources have been extensively studied, little attention has been given to the GRB jet itself as a GW source. We expect the acceleration of the jet to produce a Gravitational Wave Memory signal. While all relativistic jet models display antibeaming of GW radiation away from the jet axis, thus radiating away from directions of GRBs’ $\gamma$ radiation, this effect is not overwhelming. The decrease of the signal amplitude toward the cone of $\gamma$-ray detectability is weak, and for some models and parameters the GW signal reaches a significant amplitude for much of the $\gamma$-ray cone. Thus both signals may be jointly detected. We find different waveforms and Fourier signatures for uniform jets and structured jet models—thus offering a method of using GW signatures to probe the internal structure and acceleration of GRB jets. The GW signal peaks just outside the jet (core) of a uniform (structured) jet. Within the jet (core) the GW signal displays wiggles, due to a polarization effect; thus for a uniform jet, the peak amplitude accompanies a smoother signal than the peak of a structured jet. For the most probable detection angle and for typical GRB parameters, we expect frequencies $\lesssim 600\mathrm{Hz}$ and amplitudes $h\sim {10}^{-25}$. Our estimates of the expected signals suggest that the signals are not strong enough for a single cluster of DECIGO nor for aLIGO’s sensitivities. However, sensitivities of $\sim {10}^{-25}/\sqrt{\mathrm{Hz}}$ in the DECIGO band should suffice to detect typical long GRBs at 2 Gpc and short GRBs at 200 Mpc, implying a monthly event of a long GRB and a detection of a short GRB every decade. In addition, we expect much more frequent detection of GW from GRBs directed away from us, including orphan afterglows. The ultimate DECIGO sensitivy should increase the range and enable detecting these signals in all models even to high cosmological $z$.

Second and third generation gravitational wave interferometric detectors will be limited in their sensitivity by thermal noise of the core optics. One way to reduce this contribution is to use an input laser beam with a more uniform distribution of the power: for this reason the use of the Laguerre-Gauss ${\mathrm{LG}}_{3,3}$ mode as interferometer input has been suggested. The main issue with this approach is the fact that in resonant cavities with spherical mirrors the input mode will be degenerate with nine other modes. This implies very stringent requirements on the mirror surface quality, beyond the present polishing technology capabilities: it is not possible to obtain mirrors with low enough surface roughness to meet the requirements for the operation of a gravitational wave detector. In a previous paper an approach to apply in situ thermal corrections to the main surface of the mirrors was proposed. In this paper we develop further the technique, showing that it is possible to compute the optimal correction using only the information that can be extracted from the intensity images in reflection of the resonant cavity, without any a priori knowledge of the mirror surface maps. We test our proposal using optical simulations and we are able to considerably improve the quality of the beam reflected from a cavity with realistic mirror surface maps: without any correction the purity of the reflected beam was degraded to below 90%; with the proposed adaptive optics system we could recover a purity of 99.96%. The implementation of the proposed system would allow the use of a ${\mathrm{LG}}_{3,3}$ input mode with the mirror qualities available today. In addition we show that it is possible to correct the aberrations introduced by both mirrors acting only on one of the two. In this way it is possible to avoid introducing unwanted thermal lensing in the input mirrors.

Ultralight axions ($m_a\lesssim {10}^{-18}\mathrm{eV}$), motivated by string theory, can be a powerful probe of the energy scale of inflation. Here it is shown that in contrast to heavier axions the isocurvature modes in the ultralight axions can coexist with observable gravitational waves. Large-scale structure constraints severely limit the parameter space for axion mass, density fraction, and isocurvature amplitude. It is also shown that radically different cosmic microwave background observables for the ultralight axion isocurvature mode additionally reduce this space. The results of a new, accurate, and efficient method to calculate this isocurvature power spectrum are presented and can be used to constrain ultralight axions and inflation.

We first show that stationary black holes satisfy an extremely simple quasilocal form of the first law, $\delta E=\frac{\overline{\kappa }}{8\pi }\delta A$, where the (quasilocal) energy $E=A/(8\pi \ell )$ and (local) surface gravity $\overline{\kappa }=1/\ell$, with $A$ the horizon area and $\ell$ is a proper length characterizing the distance to the horizon of a preferred family of quasilocal observers suitable for thermodynamical considerations. Our construction is extended to the more general framework of isolated horizons. The local surface gravity is universal. This has important implications for semiclassical considerations of black hole physics as well as for the fundamental quantum description arising in the context of loop quantum gravity.

A triple-product correlation in the radiative $\beta$ decay rate of neutrons or of nuclei, characterized by the kinematical variable $\xi \equiv ({\mathbf{l}}_{\nu }\times {\mathbf{l}}_e)·\mathbf{k}$, where, e.g., $n(p)\to p(p^{\prime })+e^{-}(l_e)+{\overline{\nu }}_e(l_{\nu })+\gamma (k)$, can be generated by the pseudo-Chern-Simons term found by Harvey, Hill, and Hill as a consequence of the baryon vector current anomaly and $SU(2{)}_L\times U(1{)}_Y$ gauge invariance at low energies. The correlation probes the imaginary part of its coupling constant, so that its observation at anticipated levels of sensitivity would reflect the presence of sources of $CP$ violation beyond the standard model. We compute the size of the asymmetry in $n\to p{e}^{-}{\overline{\nu }}_e\gamma$ decay in chiral effective theory, compare it with the computed background from standard-model final-state interactions, and consider the new physics scenarios which would be limited by its experimental study.

We advocate the use of Daubechies wavelets as a basis for treating a variety of problems in quantum field theory. This basis has both natural large-volume and short-distance cutoffs, has natural partitions of unity, and the basis functions are all related to the fixed point of a linear renormalization group equation.

The light axigluon model is a viable candidate to explain the Tevatron $t\overline{t}$ forward-backward asymmetry. In this paper we present the forward-backward asymmetries for $b\overline{b}$ and $c\overline{c}$ systems predicted by a broad light axigluon with mass 100–400 GeV. Furthermore, we modify this flavor-universal axigluon model to include flavor-changing couplings of axigluons with the Standard Model quarks. We constrain these couplings from the available neutral-meson mixing data, and investigate their effects on the rare decay $B_s^0\to {\mu }^{+}{\mu }^{-}$, $CP$-violating $D\to h^{+}{h}^{-}$ and isospin-violating $B\to K^{(*)}{\mu }^{+}{\mu }^{-}$ decays. We show that a light axigluon can contribute to the observed $CP$ violation in $D\to h^{+}{h}^{-}$.

It has been speculated that Lorentz-invariance violation (LIV) might be generated by quantum-gravity (QG) effects. As a consequence, particles may not travel at the universal speed of light. In particular, superluminal extragalactic neutrinos would rapidly lose energy via the bremssthralung of electron-positron pairs ($\nu \to \nu e^{+}{e}^{-}$), damping their initial energy into electromagnetic cascades, a figure constrained by Fermi-Large Area Telescope data. We show that the two cascade neutrino events with energies around 1 PeV recently detected by IceCube—if attributed to extragalactic diffuse events, as it appears likely—can place the strongest bound on LIV in the neutrino sector, namely, $\delta =(v^2-1)<\mathcal{O}({10}^{-18})$, corresponding to a QG scale $M_{\mathrm{QG}}\gtrsim {10}^5{M}_{\mathrm{Pl}}$ ($M_{\mathrm{QG}}\gtrsim {10}^{-4}{M}_{\mathrm{Pl}}$) for a linear (quadratic) LIV, at least for models inducing superluminal neutrino effects ($\delta >0$).

We consider the problem of calculating the large number of Wick contractions necessary to compute states with the quantum numbers of many baryons in lattice QCD. We consider a constructive approach and a determinant-based approach and show that these methods allow the required contractions to be performed in a computationally manageable amount of time for certain choices of interpolating operators. Examples of correlation functions computed using these techniques are shown for the quantum numbers of the light nuclei, ${}^4\mathrm{He}$, ${}^8\mathrm{Be}$, ${}^{12}\mathrm{C}$, ${}^{16}\mathrm{O}$, and ${}^{28}\mathrm{Si}$.

The extraction of the finite temperature heavy quark potential from lattice QCD relies on a spectral analysis of the Wilson loop. General arguments tell us that the lowest lying spectral peak encodes, through its position and shape, the real and imaginary parts of this complex potential. Here we benchmark this extraction strategy using leading order hard-thermal loop (HTL) calculations. In other words, we analytically calculate the Wilson loop and determine the corresponding spectrum. By fitting its lowest lying peak we obtain the real and imaginary parts and confirm that the knowledge of the lowest peak alone is sufficient for obtaining the potential. Access to the full spectrum allows an investigation of spectral features that do not contribute to the potential but can pose a challenge to numerical attempts of an analytic continuation from imaginary time data. Differences in these contributions between the Wilson loop and gauge fixed Wilson line correlators are discussed. To better understand the difficulties in a numerical extraction we deploy the maximum entropy method with extended search space to HTL correlators in Euclidean time and observe how well the known spectral function and values for the real and imaginary parts are reproduced. Possible venues for improvement of the extraction strategy are discussed.

We derive the evolution equations for a system of neutrinos interacting among themselves and with a matter background, based upon the Bogoliubov-Born-Green-Kirkwood-Yvon hierarchy. This theoretical framework gives an (unclosed) set of first-order coupled integro-differential equations governing the evolution of the reduced density matrices. By employing the hierarchy, we first rederive the mean-field evolution equations for the neutrino one-body density matrix associated with a system of neutrinos and antineutrinos interacting with matter and with an anisotropic neutrino background. Then, we derive extended evolution equations to determine neutrino flavor conversion beyond the commonly used mean-field approximation. To this aim we include neutrino-antineutrino pairing correlations to the two-body density matrix. The inclusion of these new contributions leads to an extended evolution equation for the normal neutrino density and to an equation for the abnormal one involving the pairing mean field. We discuss the possible impact of neutrino-antineutrino correlations on neutrino flavor conversion in the astrophysical and cosmological environments, and possibly upon the supernova dynamics. Our results can be easily generalized to an arbitrary number of neutrino families.

The details are presented of a new evolution algorithm for the characteristic initial-boundary value problem based upon an affine parameter rather than the areal radial coordinate used in the Bondi-Sachs formulation. The advantages over the Bondi-Sachs version are discussed, with particular emphasis on the application to the characteristic extraction of the gravitational waveform from Cauchy simulations of general relativistic astrophysical systems.

Bosonic fields on rotating black hole spacetimes are subject to amplification by superradiance, which induces exponentially-growing instabilities (the “black hole bomb”) in two scenarios: if the black hole is enclosed by a mirror, or if the bosonic field has rest mass. Here we present a time-domain study of the scalar field on Kerr spacetime which probes ultra-long timescales up to $t\lesssim 5\times {10}^{6}M$, to reveal the growth of the instability. We describe a highly-efficient method for evolving the field, based on a spectral decomposition into a coupled set of $1+1\mathrm{D}$ equations, and an absorbing boundary condition inspired by the “perfectly-matched layers” paradigm. First, we examine the mirror case to study how the instability timescale and mode structure depend on mirror radius. Next, we examine the massive-field, whose rich spectrum (revealed through Fourier analysis) generates “beating” effects which disguise the instability. We show that the instability is clearly revealed by tracking the stress-energy of the field in the exterior spacetime. We calculate the growth rate for a range of mass couplings, by applying a frequency-filter to isolate individual modal contributions to the time-domain signal. Our results are in accord with previous frequency-domain studies which put the maximum growth rate at ${\tau }^{-1}\approx 1.72\times {10}^{-7}(GM/c^3{)}^{-1}$ for the massive scalar field on Kerr spacetime.