49 research outputs found

### Analytical template for gravitational-wave echoes: signal characterization and prospects of detection with current and future interferometers

Gravitational-wave echoes in the post-merger ringdown phase are under intense
scrutiny as probes of near-horizon quantum structures and as signatures of
exotic states of matter in ultracompact stars. We present an analytical
template that describes the ringdown and the echo signal for nonspinning
objects in terms of two physical parameters: the reflectivity and the redshift
at the surface of the object. We characterize the properties of the template
and adopt it in a preliminary parameter estimation with current (aLIGO) and
future (Cosmic Explorer, Einstein Telescope, LISA) gravitational-wave
detectors. For fixed signal-to-noise ratio in the post-merger phase, the
constraints on the model parameters depend only mildly on the details of the
detector sensitivity curve, but depend strongly on the reflectivity. Our
analysis suggests that it might be possible to detect or rule out Planckian
corrections at the horizon scale for perfectly-reflecting ultracompact objects
at $5\sigma$ confidence level with Advanced LIGO/Virgo. On the other hand,
signal-to-noise ratios in the ringdown phase equal to $\approx 100$ (as
achievable with future interferometers) might allow us to probe near-horizon
quantum structures with reflectivity $\gtrsim30\%$ ($\gtrsim85\%$) at $2\sigma$
($3\sigma$) level.Comment: v3: 13+4 pages, 11 figures, 4 appendices; matches the PRD version
with a new plot and extended results. v2 (submitted version): 12 pages + 4
appendices; 9 figures. Further discussion and new appendix with template for
localized sources at generic position. Template and waveforms available at
https://www.darkgra.org/gw-echo-catalogue.htm

### Impact of transforming to conformal Fermi coordinates on quasisingle field non-Gaussianity

In general relativity predictions for observable quantities can be expressed in a coordinate independent way. Nonetheless it may be inconvenient to do so. Using a particular frame may be the easiest way to connect theoretical predictions to measurable quantities. For the cosmological curvature bispectrum such frame is described by the Conformal Fermi Coordinates. In single field inflation it was shown that going to this frame cancels the squeezed limit of the density perturbation bispectrum calculated in Global Coordinates. We explore this issue in quasi single field inflation when the curvaton mass and the curvaton-inflaton mixing are small. In this case, the contribution to the bispectrum from the coordinate transformation to Conformal Fermi Coordinates is of the same order as that from the inflaton-curvaton interaction term but does not cancel it

### Impact of transforming to Conformal Fermi Coordinates on Quasi-Single Field Non-Gaussianity

In general relativity predictions for observable quantities can be expressed
in a coordinate independent way. Nonetheless it may be inconvenient to do so.
Using a particular frame may be the easiest way to connect theoretical
predictions to measurable quantities. For the cosmological curvature bispectrum
such frame is described by the Conformal Fermi Coordinates. In single field
inflation it was shown that going to this frame cancels the squeezed limit of
the density perturbation bispectrum calculated in Global Coordinates. We
explore this issue in quasi single field inflation when the curvaton mass and
the curvaton-inflaton mixing are small. In this case, the contribution to the
bispectrum from the coordinate transformation to Conformal Fermi Coordinates is
of the same order as that from the inflaton-curvaton interaction term but does
not cancel it.Comment: 13 pages, 2 figure

### Regularization Scheme Dependence of the Counterterms in the Galaxy Bias Expansion

In this paper we explore how different regularization prescriptions affect
the counterterms in the renormalization of the galaxy bias expansion. We work
in the context of primordial local non-Gaussianity including non-linear
gravitational evolution. We carry out the one-loop renormalization of the field
$\delta_\rho^2$ (i.e. the square of the matter overdensity field) up to third
order in gravitational evolution. Three regularization schemes are considered
and their impact on the values of the counterterms is studied. We explicitly
verify that the coefficients of the non-boost invariant operators are
regularization scheme independent.Comment: 17 pages, 10 figures. Corrected few typos. The article is now updated
to match the journal versio

### Analytical model for gravitational-wave echoes from spinning remnants

Gravitational-wave echoes in the postmerger signal of a binary coalescence are predicted in various scenarios, including near-horizon quantum structures, exotic states of matter in ultracompact stars, and certain deviations from general relativity. The amplitude and frequency of each echo is modulated by the photon-sphere barrier of the remnant, which acts as a spin- and frequency-dependent high-pass filter, decreasing the frequency content of each subsequent echo. Furthermore, a major fraction of the energy of the echo signal is contained in low-frequency resonances corresponding to the quasinormal modes of the remnant. Motivated by these features, in this work we provide an analytical gravitational-wave template in the low-frequency approximation describing the postmerger ringdown and the echo signal of a spinning ultracompact object. Besides the standard ringdown parameters, the template is parametrized in terms of only two physical quantities: the reflectivity coefficient and the compactness of the remnant. We discuss novel effects related to the spin and to the complex reflectivity, such as a more involved modulation of subsequent echoes, the mixing of two polarizations, and the ergoregion instability in the case of perfectly reflecting spinning remnants. Finally, we compute the errors in the estimation of the template parameters with current and future gravitational-wave detectors using a Fisher matrix framework. Our analysis suggests that models with almost perfect reflectivity can be excluded/detected with current instruments, whereas probing values of the reflectivity smaller than 80% at the 3σ confidence level requires future detectors (Einstein Telescope, Cosmic Explorer, LISA). The template developed in this work can easily be implemented to perform a matched-filter based search for echoes and to constrain models of exotic compact objects

### Finite Naturalness and Quark-Lepton Unification

We study the implications of finite naturalness in Pati-Salam models where
SU(3)c is embedded in SU(4). For the minimal realization at low scale of
quark-lepton unification, which employs the inverse seesaw for neutrino masses,
we find that radiative corrections to the Higgs boson mass are at least $\delta
m_h^2/m_h^2 \sim {\cal O}(10^3)$. We find that the one-loop contributions to
the Higgs mass are suppressed by four powers of the hypercharge gauge coupling.
Naively, the two-loop contributions involving the heavy vector bosons are
large. We find that for the vector leptoquarks these two-loop corrections
cancel when the Dirac Yukawa couplings for neutrinos are equal to the up-type
quark Yukawa couplings as predicted in the minimal theory for quark-lepton
unification. We show that the two-loop corrections to the Higgs mass involving
the new heavy neutral gauge boson are suppressed. We mention a way to relax the
lower bound on the vector leptoquark mass and have $\delta m_h^2/m_h^2 \sim
{\cal O}(1)$.Comment: 8 page

### Analytical model for gravitational-wave echoes from spinning remnants

Gravitational-wave echoes in the postmerger signal of a binary coalescence are predicted in various scenarios, including near-horizon quantum structures, exotic states of matter in ultracompact stars, and certain deviations from general relativity. The amplitude and frequency of each echo is modulated by the photon-sphere barrier of the remnant, which acts as a spin- and frequency-dependent high-pass filter, decreasing the frequency content of each subsequent echo. Furthermore, a major fraction of the energy of the echo signal is contained in low-frequency resonances corresponding to the quasinormal modes of the remnant. Motivated by these features, in this work we provide an analytical gravitational-wave template in the low-frequency approximation describing the postmerger ringdown and the echo signal of a spinning ultracompact object. Besides the standard ringdown parameters, the template is parametrized in terms of only two physical quantities: the reflectivity coefficient and the compactness of the remnant. We discuss novel effects related to the spin and to the complex reflectivity, such as a more involved modulation of subsequent echoes, the mixing of two polarizations, and the ergoregion instability in the case of perfectly reflecting spinning remnants. Finally, we compute the errors in the estimation of the template parameters with current and future gravitational-wave detectors using a Fisher matrix framework. Our analysis suggests that models with almost perfect reflectivity can be excluded/detected with current instruments, whereas probing values of the reflectivity smaller than 80% at the 3σ confidence level requires future detectors (Einstein Telescope, Cosmic Explorer, LISA). The template developed in this work can easily be implemented to perform a matched-filter based search for echoes and to constrain models of exotic compact objects

### Ultra-deep Large Binocular Camera U-band Imaging of the GOODS-North Field: Depth vs. Resolution

We present a study of the trade-off between depth and resolution using a
large number of U-band imaging observations in the GOODS-North field
(Giavalisco et al. 2004) from the Large Binocular Camera (LBC) on the Large
Binocular Telescope (LBT). Having acquired over 30 hours of data (315 images
with 5-6 mins exposures), we generated multiple image mosaics, starting with
the best atmospheric seeing images (FWHM $\lesssim$0.8"), which constitute
$\sim$10% of the total data set. For subsequent mosaics, we added in data with
larger seeing values until the final, deepest mosaic included all images with
FWHM $\lesssim$1.8" ($\sim$94% of the total data set). From the mosaics, we
made object catalogs to compare the optimal-resolution, yet shallower image to
the lower-resolution but deeper image. We show that the number counts for both
images are $\sim$90% complete to $U_{AB}$ $\lesssim26$. Fainter than
$U_{AB}$$\sim$ 27, the object counts from the optimal-resolution image start to
drop-off dramatically (90% between $U_{AB}$ = 27 and 28 mag), while the deepest
image with better surface-brightness sensitivity ($\mu^{AB}_{U}$$\lesssim$ 32
mag arcsec$^{-2}$) show a more gradual drop (10% between $U_{AB}$ $\simeq$ 27
and 28 mag). For the brightest galaxies within the GOODS-N field, structure and
clumpy features within the galaxies are more prominent in the
optimal-resolution image compared to the deeper mosaics. Finally, we find - for
220 brighter galaxies with $U_{AB}$$\lesssim$ 24 mag - only marginal
differences in total flux between the optimal-resolution and lower-resolution
light-profiles to $\mu^{AB}_{U}$$\lesssim$ 32 mag arcsec$^{-2}$. In only 10% of
the cases are the total-flux differences larger than 0.5 mag. This helps
constrain how much flux can be missed from galaxy outskirts, which is important
for studies of the Extragalactic Background Light.Comment: 24 pages, 14 figures, submitted to PASP, comments welcom

### Escala de avaliação da qualidade de vida por meio da Teoria da Resposta ao Item

O objetivo deste estudo foi criar uma escala para medir a qualidade de vida (QV) por meio da Teoria da Resposta ao Item (TRI). Para isso, foram coletados dados de 940 profissionais de Educação Física (PEF) registrados no Conselho Regional de Educação Física de Santa Catarina (CREF3-SC) em 2012, por meio do questionário WHOQOL-Bref. Para o tratamento dos dados, foi utilizado os recursos da TRI, com base no modelo de resposta gradual (MRG). Os resultados possibilitaram a criação de uma escala com 26 itens, com quatro categorias ordinais, em cinco níveis da escala. Na amostra dos PEF, os itens mais comuns na QV foram aqueles associados à dor física, à necessidade de tratamento médico e à capacidade de locomoção. Os itens mais incomuns foram aqueles associados às questões do ambiente físico, acesso aos serviços de saúde e questão financeira. O WHOQOL-Bref e o MRG mostraram-se adequados e forneceram recursos necessários à construção da escala de qualidade de vida