R M Marinho

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.

Status Report of the Schenberg Gravitational Wave Antenna

Here we present a status report of the Schenberg antenna. In the past three years it has gone to a radical upgrading operation, in which we have been installing a 1K pot dilution refrigerator, cabling and amplifiers for nine transducer circuits, designing a new suspension and vibration isolation system for the microstrip antennas, and developing a full set of new transducers, microstrip antennas, and oscillators. We are also studying an innovative approach, which could transform Schenberg into a broadband gravitational wave detector.

The Brazilian spherical detector: progress and plans

We are building the Schenberg gravitational wave detector at the Physics Institute of the University of Sao Paulo as programmed by the Brazilian Graviton Project. The antenna and its vibration isolation system are already built, and we have made a first cryogenic run for an overall test, in which we measured the antenna mechanical Q (figure of merit). We also have built a 10.21 GHz oscillator with phase noise performance better than -120 dBc at 3.2 kHz to pump an initial CuA16% two-mode transducer. We plan to prepare this spherical antenna for a first operational run at 4.2 K with a single transducer and an initial target sensitivity of h ∼ 2 x 10 -21 Hz -1/2 in a 50 Hz bandwidth around 3.2 kHz soon. Here we present details of this plan and some recent results of the development of this project.

Polarization states of gravitational waves with a massive graviton

Using the Newman–Penrose formalism, we obtain explicit expressions for the polarization modes of weak, plane gravitational waves with a massive graviton. Our analysis is restricted to a specific bimetric theory whose term of mass for the graviton appears as an effective extra contribution to the stress–energy tensor. For this theory we find that the extra states of polarization have amplitudes several orders of magnitude smaller than purely general relativity (GR) polarizations, h+ and h×, in the VIRGO–LIGO frequency band. This result appears using the best limit to the graviton mass inferred from solar system observations and if we consider that all the components of the metric perturbation have the same amplitude h. However, if we consider low frequency gravitational waves (e.g., fGW ~ 10−7 Hz), the extra polarization states produce similar Newman–Penrose amplitudes to purely GR polarization states. This particular characteristic of the bimetric theory studied here could be used, for example, to directly impose limits on the mass of the graviton from future experiments that study the cosmic microwave background (CMB).

The Brazilian gravitational wave detector Mario Schenberg : status report

The Mario Schenberg gravitational wave detector has been constructed at its site in the Physics Institute of the University of Sao Paulo as programmed by the Brazilian Graviton Project, under the full support of FAPESP (the Sao Paulo State Foundation for Research Support). We are preparing it for a first commissioning run of the spherical antenna at 4.2 K with three parametric transducers and an initial target sensitivity of h ~ 2 × 10−21 Hz−1/2 in a 60 Hz bandwidth around 3.2 kHz. Here we present the status of this project.

Noether's theorem in classical mechanics revisited

A didatic approach to Noethers theorem in classical mechanics is derived and used to obtain the laws of conservation.

The Brazilian gravitational wave detector Mario Schenberg: progress and plans

The Schenberg gravitational wave detector is almost completed for operation at its site in the Physics Institute of the University of Sao Paulo, under the full support of FAPESP (the Sao Paulo State Foundation for Research Support). We have been working on the development of a transducer system, which will be installed after the arrival of all the microwave components and the completion of the transducer mechanical parts. The initial plan is to operate a CuAl6% two-mode parametric transducer in a first operational run at 4.2 K with nine transducers and an initial target sensitivity of h ~ 2 × 10−21 Hz−1/2 in a 50 Hz bandwidth around 3.2 kHz. Here we present details of this plan and some recent results of the development of this project.

The status of the Brazilian spherical detector

The first phase of the Brazilian Graviton Project is the construction and operation of the gravitational wave detector Mario Schenberg at the Physics Institute of the University of S?o Paulo. This gravitational wave spherical antenna is planned to feature a sensitivity better than h = 10?21 Hz?1/2 at the 3.0?3.4 kHz bandwidth, and to work not only as a detector, but also as a testbed for the development of new technologies. Here we present the status of this detector.

Mass-Radius diagram for compact stars

The compact stars represent the final stage in the evolution of ordinary stars, they are formed when a star ceases its nuclear fuel, in this point the process that sustain its stability will stop. After this, the internal pressure can no longer stand the gravitational force and the star colapses [2]. In this work we investigate the structure of these stars which are described by the equations of Tolman-Openheimer-Volkof (TOV) [1]. These equations show us how the pressure varies with the mass and radius of the star. We consider the TOV equations for both relativistic and non-relativistic cases. In the case of compact stars (white dwarfs and neutron stars) the internal pressure that balances the gravitational pressure is essentialy the pressure coming from the degeneracy of fermions. To have solved the TOV equations we need a equation of state that shows how this internal pressure is related to the energy density or mass density. Instead of using politropic equations of state we have solved the equations numericaly using the exact relativistic energy equation for the model of fermion gas at zero temperature. We obtain results for the mass-radius relation for white dwarfs and we compared with the results obtained using the politropic equations of state. In addition we discussed a good fit for the mass-radius relation.

INVESTIGATION OF THE EXISTENCE OF HYBRID STARS USING NAMBU–JONA–LASINIO MODELS

We investigate the hadron-quark phase transition inside neutron stars and obtain mass-radius relations for hybrid stars. The equation of state for the quark phase using the standard NJL model is too soft leading to an unstable star and suggesting a modification of the NJL model by introducing a momentum cutoff dependent on the chemical potential. However, even in this approach, the instability remains. In order to remedy the instability we suggest the introduction of a vector coupling in the NJL model, which makes the EoS stiffer, reducing the instability. We conclude that the possible existence of quark matter inside the stars require high densities, leading to very compact stars.