Guilherme Frederico Marranghello

The Schenberg spherical gravitational wave detector: the first commissioning runs

Here we present a status report of the first spherical antenna project equipped with a set of parametric transducers for gravitational detection. The Mario Schenberg, as it is called, started its commissioning phase at the Physics Institute of the University of Sao Paulo, in September 2006, under the full support of FAPESP. We have been testing the three preliminary parametric transducer systems in order to prepare the detector for the next cryogenic run, when it will be calibrated. We are also developing sapphire oscillators that will replace the current ones thereby providing better performance. We also plan to install eight transducers in the near future, six of which are of the two-mode type and arranged according to the truncated icosahedron configuration. The other two, which will be placed close to the sphere equator, will be mechanically non-resonant. In doing so, we want to verify that if the Schenberg antenna can become a wideband gravitational wave detector through the use of an ultra-high sensitivity non-resonant transducer constructed using the recent achievements of nanotechnology.

Determining the neutron star equation of state using the narrow-band gravitational wave detector Schenberg

We briefly review the properties of quasi-normal modes of neutron stars and black holes. We analyse the consequences of a possible detection of such modes via the gravitational waves associated with them, especially addressing our study to the Brazilian spherical antenna, on which a possible detection would occur at 3.0-3.4 kHz. A question related to any putative gravitational wave detection concerns the source that produces it. We argue that, since the characteristic damping times for the gravitational waves of neutron stars and black holes are different, a detection can distinguish between them, and also distinguish the neutron stars oscillating modes. Moreover, since the source can be identified by its characteristic damping time, we are able to extract information about the neutron star or black hole. This information would lead, for example, to a strong constraint in the nuclear matter equation of state, namely the compression modulus should be K=220 MeV.

CONSTRAINTS ON THE HYPERON-SIGMA MESON COUPLING BY GW OBSERVATIONS

The next generation of gravitational wave observatories are promissing candidates to make the first detections. Once the detection occurs the GW characteristics permit to extract some information about the gravitational wave source. In the present work we focus on waves produced by neutron stars which can give stringent constraints on the nuclear matter equation of state. The microscopic description is based on a nonlinear field-theoretical model in order to construct such an equation of state. The model has free parameters, which from actual knowledge may not be pinned down by direct nuclear matter experiments. An important example is the hyperon-sigma meson coupling constant, currently determined by the spin-isospin SU(6) scheme. The coupling constant is of significant relevance for the structure of the equation of state, controlling its rigidity and, consequently, the properties of neutron stars and gravitational wave signals. We show, in this work, how one can constrain the hyperon-sigma meson coupling constant assuming the detection of a gravitational wave.

Isospin constraints on the parametric coupling model for nuclear matter

We make use of isospin constraints to study the parametric coupling model and the properties of asymmetric nuclear matter. Besides the usual constraints for nuclear matter\char22{}the effective nucleon mass and the incompressibility at saturation density\char22{}and the neutron star constraints\char22{}maximum mass and radius\char22{}we study the properties related to the symmetry energy. These properties constrain the parameters of the model to a small range. We apply our results to study thermodynamic instabilities in the liquid-gas phase transition as well as neutron star configurations.

Hydrodynamical collapse of neutron stars due to hadron-quark phase transition

We present studies of the collapse of neutron stars that undergo a hadron-quark phase transition. A spherical Lagrangian hydrodynamic code has been written. As initial condition we take different neutron star configurations taking into account its density, energy density and pressure distribution. The phase transition is imposed at different evolution times. We have found that a significant amount of matter on the surface can be ejected while the remaining star rings in the fundamental and first pressure modes.

Medindo a aceleração de um elevador

We present the process of measuring the acceleration of an elevator developed with the use of electronic and computing resources available on a tablet and the use of an application called Physics Toolbox Accelerometer developed for the Android operating system. The data collected with the use of electronic sensors embedded in the tablet were conveniently treated by the computer program SciDAVis. The methodology has shown to be potentially promising for practices of teaching physics that seek innovation in the teaching laboratory through the use of emerging technologies with low costs.

Investigando o impulso em crash tests utilizando vídeo-análise

We use videos that are available on the web to investigate the crash tests of cars and the properties of the impulse of a force. Although it is rarely addressed in the classroom, for automobile collisions this topic has a possibility of application in real and important problems to the understanding of phenomena of our everyday lives. Also, according to the PCN+, the airbag device would be an excellent example to illustrate the properties of the impulse. To investigate this problem, we use the Tracker free software, through which we determine some physical properties as position, velocity and acceleration related to the movement of cars and dummies used in these tests.

O movimento aparente da Lua

We investigate the motion of the Moon in its orbit around the Earth and how it sets when we locate our reference system on earth, the apparent motion of the Moon. The orbit of the Moon around the Earth is also a problem more complex than it is generally assumed, so that its motion as seen from the Earth also becomes complex. We determine an equation that describes the point of closest approach of the Moon at the zenith, as a function of time and latitude of the place. This equation takes into account the rotation of the Moon around the Earth and the variation of the inclination axis of its orbit with respect to the plane of terrestrial orbit. We compare the results with the data extracted from the software Stellarium. Finally, we estimate the current tilt of the axis of the orbit of the Moon relative to the plane of the Earth.

HEAVY ION CONSTRAINTS IN THE PARAMETRIC COUPLING MODEL

The relativistic parametric coupling model is used here to describe global static properties of nuclear matter and neutron stars. Using recent observational data related to neutron star properties and experimental results of heavy-ion collisions, we review some properties of the effective model and we impose this way new constraints on its coupling constants. Then we analyze the consequences on already known parameters of nuclear matter, i.e., the compression modulus, the effective nucleon mass, and the maximum neutron star mass predicted by integrating the Tolman–Oppenheimer–Volkoff equations. To achieve this goal, we have explored the parametric coupling model in a wide range of parameters. We made use of recent data on flow analysis to constraint this parameter. Our results indicate values for the compression modulus of nuclear matter and for the maximum mass of neutron stars which are in good agreement with the observational data.

PARAMETRIC COUPLING MODEL: RECENT ADVANCES

We review the properties of the parametric coupling model and analyze its results when considering neutron star observations and heavy-ion collision experiments, specially those concerning the isospin characteristics of symmetric and asymmetric nuclear matter. By the end of the analysis, we are able to constrain the free parameters to a very small range of acceptable values.