1,721,388 research outputs found
Generalization of the Kaiser Rocket effect in general relativity in the wide-Angle galaxy 2-point correlation function
No full textWe study wide-angle correlations in the galaxy power spectrum in redshift space, including all general relativistic effects and the Kaiser Rocket effect in general relativity. We find that the Kaiser Rocket effect becomes important on large scales and at high redshifts, and leads to new contributions in wide-Angle correlations. We believe this effect might be very important for future large volume surveys
On systematic and GR effects on muon g − 2 experiments
Full text linkWe derive in full generality the equations that govern the time dependence of the energy E of the decay electrons in a muon g − 2 experiment. We include both electromagnetic and gravitational effects and we estimate possible systematics on the measurements of a ≡ (g − 2)/2, whose experimental uncertainty will soon reach ∆a/a ≈ 10−7 . In addition to the standard modulation of E when the motion is orthogonal to a constant magnetic field B, with angular frequency ωa = ea|B|/m, we study effects due to: (1) a non constant muon γ factor, in presence of electric fields E, (2) a correction due to a component of the muon velocity along B (the “pitch correction”), (3) corrections to the precession rate due to E fields, (4) non-trivial spacetime metrics. Oscillations along the radial and vertical directions of the muon lead to oscillations in E with a relative size of order 10−6 , for the BNL g − 2 experiment. We then find a subleading effect in the “pitch” correction, leading to a frequency shift of ∆ωa/ωa ≈ O(10−9 ) and subleading effects of about ∆ωa/ωa ≈ few × O(10−8–10−9 ) due to E fields. Finally we show that GR effects are dominated by the Coriolis force, due to the Earth rotation with angular frequency ωT , leading to a correction of about ∆ωa/ωa ≈ ωT /(γωa) ≈ O(10−12). A similar correction might be more appreciable for future electron g − 2 experiments, being of order ∆ωa/ωa,el ≈ ωT /(ωa,el) ≈ 7 × 10−13, compared to the present experimental uncertainty, ∆ael/ael ≈ 10−10, and forecasted to reach soon ∆ael/ael ≈ 10−1
The large-scale monopole of the power spectrum in a Euclid-like survey: Wide-angle effects, lensing, and the 'finger of the observer'
Full text linkRadial redshift-space distortions due to peculiar velocities and other light-cone effects shape the maps we build of the Universe. We address the open question of their impact onto the monopole moment of the galaxy power spectrum, P0(k). Specifically, we use an upgraded numerical implementation of the liger method to generate 140 mock galaxy density fields for a full Euclid-like survey and we measure P0(k) in each of them utilizing a standard estimator. We compare the spectra obtained by turning on and off different effects. Our results show that wide-angle effects due to radial peculiar velocities generate excess power above the level expected within the plane-parallel approximation. They are detectable with a signal-to-noise ratio of 2.7 for Mpc-1. Weak-lensing magnification also produces additional power on large scales which, if the current favourite model for the luminosity function of Hα emitters turns out to be realistic, can only be detected with a signal-to-noise ratio of 1.3 at best. Finally, we demonstrate that measuring P0(k) in the standard of rest of the observer generates an additive component reflecting the kinematic dipole overdensity caused by the peculiar velocity. This component is characterized by a damped oscillatory pattern on large scales. We show that this 'finger of the observer' effect is detectable in some redshift bins and suggest that its measurement could possibly open new research directions in connection with the deteination of the cosmological parameters, the properties of the galaxy population under study, and the dipole itself
Gravitational-wave cosmological distances in scalar-tensor theories of gravity
Full text linkWe analyze the propagation of high-frequency gravitational waves (GW) in scalar-tensor theories of gravity, with the aim of examining properties of cosmological distances as inferred from GW measurements. By using symmetry principles, we first determine the most general structure of the GW linearized equations and of the GW energy momentum tensor, assuming that GW move with the speed of light. Modified gravity effects are encoded in a small number of parameters, and we study the conditions for ensuring graviton number conservation in our covariant set-up. We then apply our general findings to the case of GW propagating through a perturbed cosmological space-time, deriving the expressions for the GW luminosity distance dL(GW) and the GW angular distance dA(GW). We prove for the first time the validity of Etherington reciprocity law dL(GW) = (1+z)2 dA(GW) for a perturbed universe within a scalar-tensor framework. We find that besides the GW luminosity distance, also the GW angular distance can be modified with respect to General Relativity. We discuss implications of this result for gravitational lensing, focussing on time-delays of lensed GW and lensed photons emitted simultaneously during a multimessenger event. We explicitly show how modified gravity effects compensate between different coefficients in the GW time-delay formula: lensed GW arrive at the same time as their lensed electromagnetic counterparts, in agreement with causality constraints
Non-Gaussianity from the cross-correlation of the astrophysical Gravitational Wave Background and the Cosmic Microwave Background
Full text linkSince the first LIGO/Virgo detection, Gravitational Waves (GWs) have been very promising as a new complementary probe to understand our Universe. One of the next challenges of GW search is the detection and characterization of the Stochastic Gravitational Wave Background (SGWB), that is expected to open a window on the very early Universe (cosmological background) and to provide us new information on astrophysical source populations (astrophysical background). One way to characterize the SGWB and to extract information about its origin is through the cross-correlation with other cosmological probes. To this aim, in this paper, we explore the cross-correlation between the astrophysical background anisotropies and the Cosmic Microwave Background (CMB) ones. Such a signal is sensitive to primordial non-Gaussianity (nG) through the GW bias. Thus, we study the capability of next generation space-based interferometers to detect such a cross-correlation signal and to constrain primordial nG
Breaking the single clock symmetry: Measuring single-field inflation non-Gaussian features
Full text linkThe Universe is not just cold dark matter and dark energy, it also contains baryons, radiation and neutrinos. The presence of these components, beyond the pressureless cold dark matter and the quasiuniform dark energy ones, imply that the single clock assumption from inflation is no longer preserved. Here we quantify this effect and show that the single-clock symmetry is ensured only on scales where baryonic effects, neutrinos effects, or sound speed are zero. These scales depend on the cosmic epoch and the Universe composition. Hence for all use and purposes of interpreting state-of-the-art and possibly forthcoming surveys, in the accessible scales, single clock symmetry cannot be said to be satisfied. Breaking the single-clock symmetry has key consequences for the study of non-Gaussian features generated by pure single-field inflation which arise from nonlinearities in the metric yielding non-Gaussianities of the local type: the Formula Presented and the relativistic Formula Presented term
Signatures of Primordial Gravitational Waves on the Large-Scale Structure of the Universe
No full textWe study the generation and evolution of second-order energy-density perturbations arising from primordial gravitational waves. Such "tensor-induced scalar modes"approximately evolve as standard linear matter perturbations and may leave observable signatures in the large-scale structure of the Universe. We study the imprint on the matter power spectrum of some primordial models which predict a large gravitational-wave signal at high frequencies. This novel mechanism, in principle, allows us to constrain or detect primordial gravitational waves by looking at specific features in the matter or galaxy power spectrum, thereby allowing us to probe them on a range of scales unexplored so far
Non-Markovian open quantum system approach to the early Universe: Damping of gravitational waves by matter
Full text linkBy revising the application of the open quantum system approach to the early universe and extending it to the conditions beyond the Markovian approximation, we obtain a new non-Markovian quantum Boltzmann equation. Throughout the paper, we also develop an extension of the quantum Boltzmann equation to describe the processes that are irreversible at the macroscopic level. This new kinetic equation is, in principle, applicable to a wide variety of processes in the early Universe. For instance, using this equation, one can accurately study the microscopic influence of a cosmic environment on a system of cosmic background photons or stochastic gravitational waves. In this paper, we apply the non-Markovian quantum Boltzmann equation to study the damping of gravitational waves propagating in a medium consisting of decoupled ultrarelativistic neutrinos. For such a system, we study the time evolution of the intensity and the polarization of the gravitational waves. It is shown that, in contrast to intensity and linear polarization that are damped, the circular polarization ( mode) of the gravitational wave (if present) is amplified by propagating through such a medium
The Kaiser-Rocket effect: Three decades and counting
Full text linkThe peculiar motion of the observer, if not accurately accounted for, is bound to induce a well-defined clustering signal in the distribution of galaxies. This signal is related to the Kaiser rocket effect. Here we examine the amplitude and form of this effect, both analytically and numerically, and discuss possible implications for the analysis and interpretation of forthcoming cosmological surveys. For an idealistic cosmic variance dominated full-sky survey with a Gaussian selection function peaked at z ∼ 1.5 it is a > 5σ effect and it can in principle bias very significantly the inference of cosmological parameters, especially for primordial nonGaussianity. For forthcoming surveys, with realistic masks and selection functions, the Kaiser rocket is not a significant concern for cosmological parameter inference except perhaps for primordial non-Gaussianity studies. However, it is a systematic effect, whose origin, nature and imprint on galaxy maps are well known and thus should be subtracted or mitigated. We present several approaches to do so
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