Search

The LIGO gravitational wave detectors have achieved their designed sensitivity, and are currently in operation. We describe the technology of the detectors, as well as results from the analysis of some of the data collected so far. [ABSTRACT FROM AUTHOR]

Gamma-rays were first found as photons with energies in the range of tens of keV to several MeV produced by unstable nuclei. High energy photons can be produced by other types of processes, like inverse Compton scattering, expanding the γ-ray spectrum to arbitrarily high energies. [ABSTRACT FROM AUTHOR]

Our aim in this review is to briefly describe the main results in the topic of scalar field dark matter, in which a scalar field is the dark matter particle. We will start with a revision of the concept of scalar fields at the classical and quantum levels. We will then continue with some of the relevant solutions for self-gravitating scalar fields in a cosmological setting. At the end, we will discuss the constraints cosmological observations impose upon the free parameters of a scalar field dark matter model. [ABSTRACT FROM AUTHOR]

We study interacting dark energy (DE) and cold dark matter (DM) in the context of an inhomogeneous and anisotropic spacetime. DM and DE are modeled as an interactive mixture of inhomogeneous dust (DM) and a generic homogeneous dark energy (DE) fluid. By choosing an "equation of state" linking the energy density (μ) and pressure (p) of the DE fluid, as well as a free function governing the radial dependence, the models become fully determinate and can be applied to known specific DE sources, such as quintessense scalar fields or tachyonic fluids. [ABSTRACT FROM AUTHOR]

We show for the first time the evolution of non-spherically symmetric balls of a self-gravitating scalar field in the Newtonian regime. In order to do so, we use a finite differencing approximation of the Shcrödinger-Poisson (SP) system of equations with axial symmetry in cylindrical coordinates. Our results indicate that spherically symmetric equilibrium configurations of the SP system are late-time attractors for non-spherically symmetric initial profiles of the scalar field, which is a generalization of such behavior for spherically symmetric initial profiles. Our system and the boundary conditions used, work as a model of scalar field dark matter collapse after the turnaround point. In such case, we have found that spherically symmetric halos are late time attractor solutions of possible axisymmetric initial scalar field overdensities. [ABSTRACT FROM AUTHOR]

Basic aspects of strange quark matter (cold quark matter composed of roughly equal numbers of up, down and strange quarks) and the possible capture by the Earth's magnetosphere of the population of strangelets (hypothetical stable lumps of strange matter) are discussed to gauge the prospects for their detection. [ABSTRACT FROM AUTHOR]

We present results from a search for GRBs in the energy range from tens of GeVs to one TeV with an array of 6 water Cherenkov detectors located at 4500 m a.s.l. as part of the high mountain observatory of Sierra Negra (N18°59.1, W97° 18.76) near Puebla city in México. The detectors consist of light-tight cylindrical containers of 1 m2 cross section filled with 750 l of purified water; they are spaced 25 m and have a 5" photomultiplier (EMI model 9030A) facing down along the cylindrical axis. We describe preliminary experimental results obtained by using a single-particle counting technique for a data taking period of 58 days. [ABSTRACT FROM AUTHOR]

We describe the design of an extensive air shower detector array built in the Campus of the University of Puebla (located at 19°N, 90°W, 800 gcm-2) to measure the energy and arrival direction of primary cosmic rays with energies around 1015 eV. The array consists of 18 liquid scintillator detectors (12 in the first stage) and 6 water Cherenkov detectors (one of 10 m2 cross section and five smaller ones of 1.86 m2 cross section), distributed in a square grid with a detector spacing of 20 m over an area of 4000 m2. In this paper we discuss the calibration and stability of the array, and discuss the capability of hybrid arrays, such as this one consisting of water Cherenkov and liquid scintillator detectors, to allow a separation of the electromagnetic and muon components of extensive air showers. This separation plays an important role in the determination of the mass and identity of the primary cosmic ray. This facility is also used to train students interested in the field of cosmic rays. [ABSTRACT FROM AUTHOR]

Radio astronomy was the second electromagnetic window used to study the Universe and its development opened the door to the multiwavelength astronomy that characterizes much of the present day research. I briefly review the early story and achievements of radio astronomy. I also present recent astronomical discoveries obtained at radio wavelengths, as well as the characteristics and key science drivers of the next generation of radio telescopes, now under construction or design in various countries. I will also discuss the situation of this area of astronomical research in Mexico and the possibilities for the future. [ABSTRACT FROM AUTHOR]

Cosmic ray (CR) particles arrive at the top of the Earth's atmosphere at a rate of around 103 per square meter per second. They are mostly ionized nuclei - about 90% protons, 9% alpha particles traces of heavier nuclei and approximately 1% electrons. CRs are characterized by their high energies: most cosmic rays are relativistic, having kinetic energies comparable to or somewhat greater than their rest masses. A very few of them have ultrarelativistic energies extending beyond 1020 eV (tens of joules). [ABSTRACT FROM AUTHOR]

The old dream of integrating into one the study of micro and macrocosmos is now a reality. Cosmology, astrophysics and particle physics converge within a scenario (but still not a theory) of cosmic structure formation and evolution called Λ Cold Dark Matter (ΛCDM). [ABSTRACT FROM AUTHOR]

In the sections which follow, we shall be concerned predominantly with the theory of γ-ray burst sources. If the concepts there proposed are indeed relevant to an understanding of the nature of these sources, then their existence becomes inextricably linked to the metabolic pathways through which gravity, spin, and energy can combine to form collimated, ultrarelativistic outflows. These threads are few and fragile, as we are still wrestling with trying to understand non-relativistic processes, most notably those associated with the electromagnetic field and gas dynamics. If we are to improve our picture-making we must make more and stronger ties of physical theory. But in reconstructing the creature, we must be guided by our eyes and their extensions. In this introductory section we have therefore attempted to summarise the observed properties of these ultra-energetic phenomena. [ABSTRACT FROM AUTHOR]

Pulsars are rotating neutron stars (NSs) that provide unique information about their interiors, about the relativistic plasma physics of their magnetospheres, and about the intervening media through which pulses emitted by these objects must propagate. NS spins represent the clock mechanism that underlies usage of pulsars as precise timekeepers for their motions. This last topic is the final aim of this chapter, namely using pulsars to probe gravity in binary stellar systems - particularly those involving a pulsar and another compact star (white dwarf [WD], NS, or black hole [BH])- and also to probe gravitational wave backgrounds that affect the location of both the pulsar and the Earth. Pulsars also provide exquisite opportunities for probing neutron stars and their magnetospheres through a variety of techniques. [ABSTRACT FROM AUTHOR]

Nuclear astrophysics has developed in the last twenty years into one of the most important subfields of ‘applied' nuclear physics. It is a truly interdisciplinary field, concentrating on primordial and stellar nucleosynthesis, stellar evolution, and the interpretation of cataclysmic stellar events like novae and supernovae. [ABSTRACT FROM AUTHOR]

The understanding of the high energy γ-ray sky requires a coordinated multi-wavelength strategy. The Large Millimeter Telescope will be the largest and most sensitive single dish antenna operating between 0.8 mm and 3 mm in the foreseeable future. Its first light instrumentation and capabilities are well suited for studies of dust, dense molecular gas and the synchrotron emission from relativistic electrons. The Large Millimeter Telescope, due to enter commissioning and first light science phase in 2007, will be able to complement GLAST observations and help disentangling the nature of the new and old unidentified gamma-ray sources. [ABSTRACT FROM AUTHOR]

The Cygnus region of the Milky Way is prolific in star formation and presents extended diffuse γ-ray emission with a few γ-ray point sources. Among them is 3EG J2020+4017, the brightest of the unidentified EGRET sources, positionally coincident with the supernova remnant G78.2+2.1. Even though the EGRET and multi-wavelength data have not provided a conclusive identification for this γ-ray loud, but otherwise faint object, the evidence favors a pulsar like source. The EGRET photon data lack the signal-to-noise ratio required for a period search, but will serve as a valuable timing baseline extension in the case that GLAST confirms the pulsar nature of the γ-Cygni source. [ABSTRACT FROM AUTHOR]

Most approaches to camera motion estimation from image sequences require matching the projections of at least 4 non-coplanar points in the scene. The case of points lying on a plane has only recently been addressed, using mainly projective cameras. We here study what can be recovered from two uncalibrated views of a planar contour under affine viewing conditions. We prove that the affine epipolar direction can be recovered provided camera motion is free of cyclorotation. The proposed method consists of two steps: 1) computing the affinity between two views by tracking a planar contour, and 2) recovering the epipolar direction by solving a second-order equation on the affinity parameters. Two sets of experiments were performed to evaluate the accuracy of the method. First, synthetic image streams were used to assess the sensitivity of the method to controlled changes in viewing conditions and to image noise. Then, the method was tested under more realistic conditions by using a robot arm to obtain calibrated image streams, which permit comparing our results to ground truth. [ABSTRACT FROM AUTHOR]