Poster N. 1
Schenberg noise spectral density noise floor using finite element modelling
Carlos Frajuca (IFSP)
Schenberg is gravitational waves spherical resonant mass detector, with a central frequency of operation of 3200 Hz. Transducers located on the surface of the resonating sphere, according to a distribution half-dodecahedron, are used to monitor a strain amplitude. The development of mechanical impedance matchers that act by increasing the coupling of the transducers with the sphere is a major challenge because of the high frequency and small in size. The objective of this work is to study the spectral density curve deformation noise obtained by finite element modeling (FEM), compared to the result of the simplified model for mass-spring type system modeling verifying if that is suitable for the determination of sensitivity detector, as the conclusion the both modelling give the same results.
Poster N. 2
Thermal connection and vibrational isolation: a single solution for two problems
Bortoli, Fabio da Silva (IFSP)
A spherical gravitational wave (GW) detector has a heavy ball shaped mass which vibrates when a GW passes through it. Such motion is monitored by transducers and the respective electronic signal is digitally analyzed. One of such detectors, SCHENBERG, will have resonant frequencies around 3.2 kHz with a bandwidth near 200 Hz. Mário Schenberg is a spherical ressonant-mass gravitational wave detector weighting 1.15ton, being built in the Departament of Materials at the University of São Paulo. The sphere with 65cm in diameter will be made of a copper-aluminum alloy with 6 per cent Al. As a ressonant mass detectors a signal appears after the GW to pass through the detector and to produce vibrations on the ressonant mass. The ressonantes frequencies this system are around 3.2kHz with a bandwidth near 200Hz. Six transducers linked on the surface of spherical ressonant mass according a truncated icosahedron distribution are used to monitor the amplitud of it displacement. The sphere, in a commissioning fase the detector was cooled to 4.2 Kelvin. In the future, using a dilution refrigerator, this temperature could reach as low as 50 mK. However this refrigerator produces noise because of the Helium evaporation and this noise is transported by the thermal connection to the sphere. In this work we study such vibration noise and how it could be minimized. The conventional method used in detectors with this kind of refrigerator is to connect the refrigerator to the sphere using thin copper wires, but it reduces the cooling capability by a great factor. In this work a new kind of connection is propose. The vibration attenuation should make the dilution refrigerator noise lower than the thermal vibration noise on the sphere surface, keeping the temperature as lower as possible and an attenuation higher than 10^10 is found.
Poster N. 3
Overcoming limitations in gravitational wave direction determination
Carlos Filipe da Silva Costa e Nadja Simão Magalhães (UNIFESP)
Determining the direction of a gravitational wave (GW) source is necessary for confrontations between a candidate GW signal and its electromagnetic counterpart. In the context of low latency pipelines it is assumed that analytic solutions (based on the GW matrix reconstruction) can provide efficiently the GW direction. However, we identified that such analytic solutions present theoretical and practical limitations (indeterminacies) which were not previously mentioned in the literature.
Under realistic conditions, we identified that for certain incoming directions such solutions are unable to recover them. Therefore, we provide here for the first time a full review of these indeterminacy cases and explain their origins. We then propose a mathematical procedure that reduces such indeterminacies.
Taking into account the constraining requirements of a low latency pipeline, we developed a method that requires the least computational power to retrieve GW directions. The mathematical considerations and method principle can be applied to any system of detectors able to reconstruct the GW matrix. We tested it on simulated data of the GW detector Schenberg. The results show that this method cancels out indeterminacies and the direction resolution is limited by a 1/SNR law for any incoming direction. Thus it retrieves a remarkable advantage of the spherical GW antenna: the possibility of an isotropic direction determination.
Poster N. 4
Testing the Duality Relation with Clusters and H(z)
Simony Costa & Rodrigo F. L. Holanda (ON)
The so-called reciprocity relation, proved long ago by Etherington, is of fundamental importance in cosmology. It states that if the source and the observer are in relative motion, solid angles, subtended between the source and the observer are related by geometrical invariants and a factor dependent of the source redshift. Its most useful version, in the astronomical context, is known as cosmic distance duality relation (CDDR), and relates the luminosity (DL) and angular diameter (DA) distances by the following expression: $DL(z)(1 + z)^{-2}/DA(z)=1$. This relation is completely general, valid for all cosmological models based on Riemannian geometry and is independent either upon Einstein field equations other nature of matter. It only requires that source and observer be connected by null geodesics in a Riemannian spacetime and that the number of photons be conserved. In this work we propose a cosmological model-independent test for the CDDR by using galaxy clusters and expansion rate of the universe measurements, H(z). In our analysis, we use 25 angular diameter distances sample, which were obtained by considering two different morphologies, jointly with H(z) measurements, in order to investigate the influence of the morphology used to describe the galaxy clusters in the validity of the CDDR. We consider the h parameter, as a function of the redshift, in two different ways: h(z)=1+h_0z$ and h(z)=1+h_0z/(1+z)$. The results showed no evidence of violation of duality relation by considering the elliptical sample, however a slight violation of RDDC was noted when considering the sample assuming a spherical geometry.
Poster N. 5
Gravitationally Induced Particle Creation and the Generalized Second Law of Thermodynamics
Leila Graef (IF-USP), J.A.S. Lima, D. Pavon e S. Basilakos
A new cosmic scenario with gravitationally induced particle creation is proposed. In this model the Universe evolves from an early to a late time de Sitter era, with the recent accelerating phase driven only by the negative creation pressure associated with the cold dark matter component. A detailed thermodynamic analysis is carried out. For a very wide range of the free parameters, it is found that the model presents the expected behavior of an ordinary macroscopic system in the sense that it approaches thermodynamic equilibrium in the long run (i.e., as it nears the second de Sitter phase).
Poster N. 6
Preliminary study on general relativity
Iara Ota & Cecilia Chirenti (UFABC)
The aim of this work is to make an introductory approach to the theory of general relativity. In pursuing this aim, we have begun studying special relativity via the resolution of some classical problems such as the relativity of simultaneity, the distribution of stars considered from two distinct inertial frames and the Compton scattering of a foton in the outer space. Subsequently, curved spacetime, the Einstein field equations, the Schwarzschild geometry and the necessary mathematical background will be studied.
Poster N. 7
Numerical study of the gravitacional n-body problem
Carla V. Pequini e Cecilia Chirenti (UFABC)
The present project has the intention to show how Newton's law of universal gravitation operates in Kepler problem, and in central forces problem, two bodys, three bodys and n bodys problems through use of the Java program Triana which acts solving motion equations by exploiting the dynamics and evolution of the different gravitational systems. In this first part of the project development there was a focus on Kepler's laws and the study of the gravitational law at the case of the central force, two and three body system.
Poster N. 8
First Measurement of sigma 8 with supernovae magnitudes only
Tiago Batalha de Castro (UFRJ)
Using the closest 732 supernovae of the recent JLA catalog and the method of moments we show that a simple treatment of intrinsic non-Gaussianities with a couple of nuisance parameters is enough for make the first measurement σ 8 of using only SN data.
Poster N. 9
Stars in modified Gravity: curvature fluid
Sergio Joras (IF/UFRJ)
According to general relativity (GR), about 95% of our universe — if assumed homogeneous and isotropic — is made of dark components. Therefore, it is natural to look for corrections from GR to avoid this huge blank. The simplest generalization of GR is the so-called f(R) theory. In the metric approach, it yields fourth-order equations for the metric and, as such, they point out a new degree of freedom. Most of the viable modified theories are equivalent to the standard ΛCDM model in the background when one requires it to pass local tests and fitting of the mass power spectrum. We study a simple generalization of the metric exponential f(R) gravity theory that is cosmologically viable and compatible with solar system tests of gravity. As compared to other viable f(R) theories, its steep dependence on the Ricci scalar R facilitates agreement with structure constraints, opening the possibility of f(R) models with equation-of-state parameter that could be differentiated from a cosmological constant (wde = −1) with future surveys at both background and perturbative levels.
In the present work, we investigate the effect of this particular modified theory in relativistic stars, namely the mass-radius diagram, the stable branch and the distribuition of the effective curvature fluid.
Poster N. 10
Constraining cosmic deceleration-acceleration transition with type Ia supernova, BAO/CMB and H(z) data
M. Vargas dos Santos , R. R. R. Reis and I. Waga (UFRJ)
We revisit the kink-like parametrization of the deceleration parameter (q) (Ishida et al., 2008). This parametrization assumes an unique transition between two values of the deceleration parameter (at early (qi) and future (qf) times), being the transition characterized by its redshift (zt) and duration (t). We obtain constraints on these parameters using recent data from type Ia supernovae (SN Ia), baryon acoustic oscillations (BAO), cosmic microwave background (CMB) and the Hubble parameter (H(z)). The use of H(z) data introduces an explicit dependence of the combined likelihood on the present value of the Hubble parameter (H0), allowing us to explore the influence of different priors when marginalizing over this parameter. We also study the importance of the CMB information in the results by considering data from WMAP7, WMAP9 (Wilkinson Microwave Anisotropy Probe - 7 and 9 years) and the Planck satellite. As expected, we show that Planck gives more stringent constraints. Assuming a flat space geometry, qi =1/2 and expressing the current value of q (q0) as a function of the other parameters, we obtain zt = 0.68 ± 0.12, t=0.25+0.18}_{-0.13}$ and $q0=-0.50+0.14_{-0.16}$, at 68% of confidence level, with flat prior on H0.
Poster N. 11
Influence of the Box Size and Overdensity in Cosmological Simulations
Guido Granda Muñoz (ON), Josef Stoeckl , Sabine Schindler
In this work, we study the influence of the box size and overdensity in cosmological simulations. The aim of this work is to study their influence in cosmological simulations on both the dark matter and baryonic matter components; to study their effect we compared different properties for both dark and baryonic matter in different simulation volumes. This work involves data from cosmological simulations where dark matter has been pre-calculated with a N-body code (GADGET2), and where baryonic matter were evolved with a grid-based hydrodynamical code (FLASH). We found that a small the box size and high overdensity in cosmological simulations yield a dynamical delay. This can be clearly seem on the various properties studied here; they affect their values and statistics, which can produce wrong results if their influence is not taken into account.
Poster N. 12
Cosmology with Strong Lensing in Dark Energy Survey simulated images
Clécio de Bom, Martin Makler, Gabriel B. Caminha (CBPF)
Strong gravitational lensing systems with sources in different redshifts have been used to determine cosmological distance ratios, and therefore to constrain cosmological parameters. In this contribution we evaluate the possibility of probing the background cosmology with images that simulates the Dark Energy Survey (DES) observational conditions. We use images from the Cluster Lensing and Supernova Survey with Hubble (CLASH) of the galaxy cluster RXJ2248 and use the lenstool software to perform the lens modelling for sources at multiple redshifts, from which we derive the distance ratios. The CLASH HST images are degraded to the mean DES seeing and noise is added to mimic the DES depth. We derive constraints on cosmological parameters from both the original CLASH images and using the "DES simulated" images. We explore the effects on statistical and systematic errors from going tom the CLASH to the DES image and explore, separately, the effect of the decreased number of identifiable multiple images, the seeing, the signal-to-noise, and the lack of source photometric redshifts.
Poster N. 13
Effects of Completeness and Purity on Cluster Dark Energy Constraints
Michel Aguena, Marcos Lima and DES-Brazil Cluster WG
The observed statistical properties of galaxy clusters can only be used for cosmological purposes if the main observational effects related to cluster detection are accurately characterised. For optical clusters, these effects include the selection function associated to cluster finder algorithms and the survey strategy. The importance of the selection becomes apparent when different cluster finders applied to the sample parent galaxy catalog produce cluster samples with distinct statistical properties. We consider parametrised functional forms for the observable-mass relation, its scatter and the completeness and purity of cluster samples and study how prior knowledge on these function parameters affects dark energy constraints derived from cluster abundance. Whereas arbitrary evolution in these selection functions degrades much of dark energy information, simple functional forms for the selection can be reasonably well self-calibrated in current and upcoming cluster surveys, producing competitive dark energy constraints.
Poster N. 14
A combined estimator to search for primordial non-Gaussianity in Planck CMB maps
Camila Novaes, Armando Bernui, Ivan S. Ferreira, Carlos Alexandre Wuensche
We present an upgraded combined estimator, based on Minkowski Functionals and Neural Network, with excellent performance in detecting primordial non-Gaussianity in simulated maps that also contain a weighted mixture of Galactic contaminations, besides real pixel's noise from Planck cosmic microwave background radiation data. With a validated estimator's performance in a variety of cases, we look for constraining the primordial non-Gaussianity in large angular scales analyses of the Planck maps. For the SMICA map we found that ${f}_{\rm \,NL} = 44 \pm 14$, at $2\sigma$ confidence level, which is in excellent agreement with the WMAP-9yr and Planck results. In addition, for the other three Planck maps we obtain larger constraints with mean values in the interval ${f}_{\rm \,NL} \in [59, 77]$, concomitant with the fact that these maps manifest distinct features in reported analyses, like having larger pixel's noise intensity. Moreover, our results confirm, as indicated by the Planck collaboration, that different amounts of foregrounds residuals are still present in each one of the foreground-cleaned Planck maps, and that the SMICA map appears as the cleanest one.
Poster N. 15
Magnetized Neutron Stars
Gibran H. Souza (UNICAMP), Ernerto Kemp (UNICAMP), Cecilia Chirenti
Here we present the magnetic field profile for a realistic neutron star with both poloidal and toroidal components.
Poster N. 16
Cosmological constraints from angular clustering of galaxies
Hugo Camacho & Marcos Lima (IF-USP)
The analysis of angular clustering of galaxies allows for a model independent measurement of severe importance for photometric galaxy surveys where a gain in area and depth is achieved, in exchange of a poorer determination of radial positions. Some results on constraining cosmological parameters by using the information of angular clustering of galaxies at large scales on simulated data for such kind of surveys in configuration and harmonic space are presented. We focus on the importance of modeling the covariance between different angular scales in configuration space analysis. For this propose we also present an implementation of a fast Hankel transform algorithm, the FFTLog method, which allows to speed up covariances evaluation.
Poster N. 17
Statistical comparison of variational formalisms for f(R) theories
B. Santos, M. Campista, N. Chandrachani Devi, J. S. Alcaniz (ON)
It is well known that one of the main properties of the universe is its current accelerated expansion. However, the origin of this acceleration is still the biggest challenge of cosmology today. f(R) theories can explain this accelerated expansion by replacing the Ricci scalar R in the Einstein-Hilbert Lagrangian of the General Relativity for a more general f(R) function, thereby avoiding the inclusion of the dark energy. An important issue of this scenario is that the field equations that governs the cosmic dynamics in these theories depends on the variational formalism adopted. Basically, we can choose between two options: the metric formalism, where the variation of the action is performed with respect to the metric only, and the Palatini formalism, in which the metric and the connections are independent and the variation must be performed with respect both fields. It is clear, therefore, that f(R) theories brings us at least two challenges, the choice of a f(R) functional form and also the choice of a variational formalism. Until now, these two problems still lacks definition and also there is no clear indication of the solution. In this work, we compare, from a observational point of view, the Palatini and metric formalisms using some f(R) functions. For this purpose, we perform a Bayesian model selection analysis using the Affine-Invariant Monte-Carlo method. In order to obtain the parametric space and the posterior distribution for the parameters of each model, being a model constituted by the variational formalism and a f(R) function, we use the more up-to-date type Ia supernova (SNe Ia) data, the JLA compilation, containing 740 events. We also make a joint analysis combining the SNe Ia data with baryon acoustic oscillations (BAO) and also the growth of cosmological perturbations. The model selection is then performed by obtaining the Bayesian evidence of each model and computing the Bayes factor between two models.
Poster N. 18
Gas mass fraction for decaying vacuum cosmological at low-z
Rodrigo S. Gonçalves (ON)
The recent observational evidence for the current cosmic acceleration have stimulated renewed interest in alternative cosmologies, such as scenarios with interaction in the dark sector (dark matter and dark energy). In general, such models contain an unknown negative-pressure dark component coupled with the pressureless dark matter and/or with the baryons that results in an evolution for the Universe rather different from the one predicted by the standard ΛCDM model. In this work we test the observational viability of such scenarios by using a new approach for the cosmological test called gas mass fraction (Allen et al. 2002, 2008, Ettori 2009). Instead of the standard use of the gas mass fraction, here we restrict our analyzes to the low redshift range (z < 0.4). This approach leads to a cosmological independent test for the gas mass fraction. The resulting are consistent with, and typically as constraining as, those derived from other cosmological data. Although a time-independent cosmological constant (ΛCDM model) is a good fit to these galaxy cluster data, an interacting dark energy component cannot yet be ruled out. We also explore the future surveys and their improvements on the parameters analyzed.
Poster N. 19
Measuring our peculiar velocity using aberration effects on the CMB anisotropies
Omar Roldan & Miguel Quartin (UFRJ)
It is generally accepted that the observed CMB dipole arises from the Earth's motion relative to the CMB frame. Under this assumption we can infer [1,2,3] our peculiar velocity to be $\beta =(1.231\pm 0.003)\times 10^{-3}$. However it’s also possible that this dipole is not necessarily a Doppler effect but it’s (at least partially) due to a primordial anisotropy in the Universe. In this work, we review a recent proposal [4,5] for an alternative method of measuring our peculiar velocity $\beta$ by using aberration effects. This is based on the fact that our motion induces not only a dipolar effect but also a correlation among all CMB multipoles $a_{lm}$ because the primordial anisotropies are distorted by the Doppler and aberration effects. This method can be used as a consistency check for measuring our peculiar velocity and the results were confirmed by Planck observations [6]. Finally, we also look for others possible contributions to the CMB dipole like the dipolar anisotropy due to large scale isocurvature perturbations [7].
Poster N. 20
Viscous cosmology
Julio C. Fabris (UFES)
A viscous model for the dark sector of the universe may cure some of the problems of the standard cosmological model, as the excess of power in the matter agglomeration at small scales. We consider a viscous fluid in the dark sector and study its non-linear perturbative behaviour and we show that, under certain quite natural conditions, there is a suppression of sub-structures at the galactic scales.
Poster N. 21
Excitação de ondas magnetohidrodinâmicas (MHD) através de ondas gravitacionais produzidas por binárias de estrelas de nêutrons
Adam S. Gontijo e Oswaldo D. Miranda
Instituto Nacional de Pesquisas Espaciais-INPE
Ondas gravitacionais (OGs) têm provado ser os sinais mais indescritíveis na astrofísica. Mesmo sendo que a maioria das frequências eletromagnéticas são observáveis, até mesmo os raios cósmicos e os neutrinos astronômicos; as OGs, entretanto, ainda não foram detectadas diretamente. A primeira evidência indireta das OGs foi obtida com a binária de pulsares PSR 1913+16, descoberta por Hulse & Taylor (1974), que exibiu uma diminuição do período orbital, como consequência da energia gravitacional irradiada. A quantidade de decréscimo está de acordo com as predições da Relatividade Geral em 1% [4]. Aliás, a coalescência de sistemas de binárias de nêutrons (EN-EN) são objetos astronômicos que produzem quantidade significativa de OGs, que são o principal alvo para os detectores em terra de segunda geração (exemplo, Advanced LIGO). ENs também possuem contrapartida observacional, no espectro eletromagnético, desde que elas estão relacionadas com os eventos de Gamma-Ray Bursts GRBs de curta duração ( t <~ 2 seg) [1]. A detecção de forma indireta pode partir de um mecanismo que as torna "visíveis" no domínio eletromagnético. Isto é, em um plasma fortemente magnetizado circundante a uma fonte de OGs, tem seus modos (Alfvén e magneto-acústico) de ondas magnetohidrodinâmicas (MHD) excitados pelo acoplamento das polarizações´ e + das OGs [3]. A quantidade de energia da OG dissipada para o plasma pode, em seguida, irradiar esta energia na forma de ondas eletromagnéticas observáveis, isto pode prover um mecanismo interessante de ignição para abastecer um Fireball de GRB. Nós investigamos se essas distorções extremas no espaço-tempo perturbam o ambiente de campo magnético de forma significativa para produzir uma contrapartida eletromagnética observável do burst do GRB. Também tal contribuição gravitacional seria um termo a mais para permitir atingir os altos fatores de Lorentz ( G ~ 100 – 1000) observados em GRBs, questão em aberto na sociedade científica [2].
Referências
[1] C. Kouveliotou, C. A. Meegan, G. J. Fishman, N. P. Bhat, M. S. Briggs, T. M. Koshut, W. S. Paciesas, and G. N. Pendleton. Identification of two classes of gamma-ray bursts. Astrophysical Journal, 413: L101-L104, Aug. 1993. doi: 10.1086/186969.
2] J. Lü, Y.-C. Zou, W.-H. Lei, B. Zhang, Q. Wu, D.-X. Wang, E.-W. Liang, and H.-J. Lü. Lorentz-factor-Isotropic-luminosity/Energy Correlations of Gamma-Ray Bursts and Their Interpretation. Astrophysical Journal, 751:49, May 2012. doi: 10.1088/0004-637X/751/1/49.
[3] J. B. Moortgat. General Relativistic Plasma Dynamics. PhD thesis, Radboud Universiteit Nijmegen, The Netherlands, May 2006.
[4] J. H. Taylor and J. M. Weisberg. Further experimental tests of relativistic gravity using the binary pulsar PSR 1913 + 16. Astrophysical Journal, 345:434{450, Oct. 1989. doi: 10.1086/167917.