A Tighter Test of Local Lorentz Invariance using PSR J2317+1439

Gravity being a long-range force, one might {\it a priori} expect the Universe's global matter distribution to select a preferred rest frame for local gravitational physics. The phenomenology of preferred-frame effects, in the strong-gravitational field context of binary pulsars, is described by two parameters $\hat{\alpha}_1$ and $\hat{\alpha}_2$. These parameters vanish identically in general relativity, and reduce, in the weak-field limit, to the two parametrized post-Newtonian (PPN) parameters ${\alpha}_1$ and ${\alpha}_2$. We derive a limit of $|\hat{\alpha}_1| < 1.7\times 10^{-4}$ (90\%~C.L.) using the very low eccentricity binary pulsar PSR J2317+1439, improving by a factor of 3 on previous limits.Comment: 4 pages, LaTeX, requires aaspp4.sty and flushrt.sty, submitted to Ap

A new test of conservation laws and Lorentz invariance in relativistic gravity

General relativity predicts that energy and momentum conservation laws hold and that preferred frames do not exist. The parametrised post-Newtonian formalism (PPN) phenomenologically quantifies possible deviations from general relativity. The PPN parameter alpha_3 (which identically vanishes in general relativity) plays a dual role in that it is associated both with a violation of the momentum conservation law, and with the existence of a preferred frame. By considering the effects of alpha_3 neq 0 in certain binary pulsar systems, it is shown that alpha_3 < 2.2 x 10^-20 (90% CL). This limit improves on previous results by several orders of magnitude, and shows that pulsar tests of alpha_3 rank (together with Hughes-Drever-type tests of local Lorentz invariance) among the most precise null experiments of physics.Comment: Submitted to Classical Quantum Gravity, LaTeX, requires ioplppt.sty, no figure

Phenomenology of a lepton triplet

The most general phenomenological model involving a lepton triplet with hypercharge $\pm 1$ is constructed. A distinctive feature of this model is the prediction of a doubly charged lepton, and a new heavy Dirac neutrino. We study the phenomenology of these exotic leptons in both low-energy experiments and at the LHC. The model predicts FCNC processes such as rare muon decays, which are studied in detail in order to constrain the model parameters. All the decay channels of the exotic leptons are described for a wide range of parameters. It is found that, if the mixing parameters between the exotic and light leptons are not too small ($>10^{-6}$), then they can be observable to a $3-5\sigma$ statistical significance at the 7 TeV LHC with 10-50 fb$^{-1}$ luminosity for a 400 GeV mass, and 14 TeV with 100-300 fb$^{-1}$ luminosity for a 800 GeV mass.Comment: 28 pages, 17 figures. Version to appear in PR

Constraining Radio Emission from Magnetars

We report on radio observations of five magnetars and two magnetar candidates carried out at 1950 MHz with the Green Bank Telescope in 2006-2007. The data from these observations were searched for periodic emission and bright single pulses. Also, monitoring observations of magnetar 4U0142+61 following its 2006 X-ray bursts were obtained. No radio emission was detected was detected for any of our targets. The non-detections allow us to place luminosity upper limits (at 1950 MHz) of approximately L < 1.60 mJy kpc^2 for periodic emission and L < 7.6 Jy kpc^2 for single pulse emission. These are the most stringent limits yet for the magnetars observed. The resulting luminosity upper limits together with previous results are discussed, as is the importance of further radio observations of radio-loud and radio-quiet magnetars.Comment: 11 pages, 4 figure

Twenty-One Millisecond Pulsars in Terzan 5 Using the Green Bank Telescope

We have discovered 21 millisecond pulsars (MSPs) in the globular cluster Terzan 5 using the Green Bank Telescope, bringing the total of known MSPs in Terzan 5 to 24. These discoveries confirm fundamental predictions of globular cluster and binary system evolution. Thirteen of the new MSPs are in binaries, of which two show eclipses and two have highly eccentric orbits. The relativistic periastron advance for the two eccentric systems indicates that at least one of these pulsars has a mass >1.68 Msun at 95% confidence. Such large neutron star masses constrain the equation of state of matter at or beyond the nuclear equilibrium density.Comment: 12 pages, 2 figures. Accepted by Science. Published electronically via Science Express 13 Jan 200

La Vida Cotidiana de la Niñez en el Campamento "Felipe Camiroaga"

Tesis (Trabajo Social)En la presente investigación, se expondrán los antecedentes de las denominadas “Tomas” en la Quinta región y el país, enfatizando la gran cantidad de campamentos, y como se evidencia en Chile desde la historia Socio-Política, desde la “Cuestión social” y cómo se construye la problematización del fenómeno investigado, a partir de las políticas de vivienda y sus distintas falencias en el sistema económico hegemónico. Esta investigación fue realizada en el territorio denominado “Campamento Felipe Camiroaga” por la observación constante del equipo de investigación, debido a la práctica profesional realizada en el mismo lugar. En el marco teórico se trabaja desde la visión Crítico-Marxista basada en Kosik y sus distintos documentos entorno a la dialéctica. Luego, se revisan las distintas visiones de “Vida Cotidiana” principalmente por Henri Lefebvre, Michel De Certau, entre otros autores basados en el paradigma mencionado anteriormente esto llegando a la urbanización Capitalista desde el análisis de Christian Topalov y el Derecho a la ciudad. Posteriormente se detalla el enfoque metodológico cualitativo, y la etnografía como método siendo lo que más se ajusta a la investigación. El Campamento Felipe Camiroaga, en relación a otros campamentos de la región, aún no cuenta con la antigüedad suficiente para estar dentro del “Registro Nacional de Campamentos” del MINVU, a pesar de ser uno de los más grandes a nivel Nacional. Mediante un acercamiento con las y los pobladores se expone de manera innovadora al grupo de investigación la riqueza e importancia de reconstruir a través de sus miembros la historia y sobre todo visibilizar cómo se plantea la convivencia a diario en el campamento con el objetivo de recabar en las diferentes variables que se presentan como obstaculizadores y facilitadores en su diario vivir, este interés se presenta para el equipo de investigación ya que, la práctica profesional que se está realizando ha permitido observar los distintos discursos planteados por parte de las y los pobladores quienes en la situación que se encuentran, en situación de precariedad, por las diferentes experiencias personales y por una falencia esencial del Estado en las Políticas de Vivienda y urbanismo, han tomado la decisión de tomarse un terreno y vivir de manera permanente, asumiendo todos los riesgos a los que se exponen, sobre todo la falta de servicios básicos y la irregularidad a la que se enfrentan, en los discursos planteados, se visualiza un enojo con la autoridad actual tanto Local como Nacional

Discovery of 10 pulsars in an Arecibo drift-scan survey

We present the results of a 430-MHz survey for pulsars conducted during the upgrade to the 305-m Arecibo radio telescope. Our survey covered a total of 1147 square degrees of sky using a drift-scan technique. We detected 33 pulsars, 10 of which were not known prior to the survey observations. The highlight of the new discoveries is PSR J0407+1607, which has a spin period of 25.7 ms, a characteristic age of 1.5 Gyr and is in a 1.8-yr orbit about a low-mass (>0.2 Msun) companion. The long orbital period and small eccentricity (e = 0.0009) make the binary system an important new addition to the ensemble of binary pulsars suitable to test for violations of the strong equivalence principle. We also report on our initially unsuccessful attempts to detect optically the companion to J0407+1607 which imply that its absolute visual magnitude is > 12.1. If, as expected on evolutionary grounds, the companion is an He white dwarf, our non-detection imples a cooling age of least 1 Gyr.Comment: 8 pages, 3 figures, accepted for publication in MNRA