On the possibility of a maximum fundamental density and the elimination of gravitational singularities

With this note we want to point out that already in the early days of cosmology it was understood that negative pressure could eliminate gravitational singularities in a natural way e.g. E.B. Gliner, Sov. Phys. JETP 22(1966)378 and M.A. Markov, Pis'ma Zh. Eksp. Teor. Fiz. 36, No 6, 214-216 (20 Sept. 1982). Today, with the discovery of dark energy and the strong evidence in favor of an inflationary start of the Big Bang, the existence of negative pressure is widely accepted. In fundamental physics, phase transitions are generally thought to be reversible (Cf. Ellis, New Astronomy Reviews Volume 46, Issue 11, October 2002, P. 645). It seems likely then that if inflation has occurred, the process should be reversible. I.e. when the increasing density in a collapsing universe or star reaches a certain limit it should go through a phase transition to a medium with an equation of state of the type $p=\omega \rho$, where $-1< \omega <-1/3$. If this phase transition is fundamental, i.e. occurs for all energy densities, a collapse will always reach a minimum radius and bounce. If the phase transition is symmetric, the result will lead to oscillating universes. If however the phase transition is associated with an hysteresis effect, a collapsing star may, succeeding the bounce inflate into a new universe with a subsequent phase transition becomes dominated by ordinary relativistic matter. The aim of this note is study the time development of a model which mimics this process.Comment: 5 pages, 2 figures. Replaced since the Abstract is updated and further references are included. There are also some minor changes in the tex

Detection of CO (J=1-0) in the dwarf elliptical galaxy NGC 185

The detection of CO (J = 1-0) emission in the dwarf elliptical galaxy NGC 185 is reported. The presence of massive molecular clouds in this early-type galaxy supports the idea of recent or ongoing stellar formation indicated by the population of blue stars in the center. The CO was detected in two positions in the galaxy, the center, and a prominent dustcloud. The emission profile has two peaks, roughly centered around the systemic velocity. It is found that NGC 185 is overluminous in blue light for its CO luminosity compared with Sc galaxies. This might indicate a higher star-formation efficiency for NGC 185 than for the late-type galaxies

Bounce inflation with a conserved frame of rest

Some form of approximately exponential inflation is generally assumed to be the origin of our present universe. The inflation is thought to be driven by a scalar field potential where the field first slowly slides along the potential and then comes to a steep slope where the field rapidly falls and then oscillates around zero transforming into particles. The slowly sliding scalar field inflation leads to an exponentially expanding de Sitter space. A scalar field as well as the deSitter space are both Lorentz invariant. Thus no global frame of rest can be established in this scenario, while particle creation requires a preferred frame of rest. Observations of the cosmic microwave background show, when the redshift is corrected for our local velocity, a very even temperature and redshift distribution requiring a global preferred frame of rest. We suggest here that a density dependent equilibrium relation between matter/radiation and a scalar energy density could maintain a preferred frame of rest throughout the bounce and inflation and thereby solve the problem.Comment: 5 pages, 4 figure

Gas and dust in the star-forming region ρ Oph A ∗, ∗∗, ∗∗∗: The dust opacity exponent β and the gas-to-dust mass ratio g2d

© ESO, 2015. Aims. We aim at determining the spatial distribution of the gas and dust in star-forming regions and address their relative abundances in quantitative terms. We also examine the dust opacity exponent β for spatial and/or temporal variations. Methods. Using mapping observations of the very dense ρ Oph A core, we examined standard 1D and non-standard 3D methods to analyse data of far-infrared and submillimetre (submm) continuum radiation. The resulting dust surface density distribution can be compared to that of the gas. The latter was derived from the analysis of accompanying molecular line emission, observed with Herschel from space and with APEX from the ground. As a gas tracer we used N<inf>2</inf>H⁺, which is believed to be much less sensitive to freeze-out than CO and its isotopologues. Radiative transfer modelling of the N<inf>2</inf>H⁺ (J = 3-2) and (J = 6-5) lines with their hyperfine structure explicitly taken into account provides solutions for the spatial distribution of the column density N(H<inf>2</inf>), hence the surface density distribution of the gas. Results. The gas-to-dust mass ratio is varying across the map, with very low values in the central regions around the core SM 1. The global average, = 88, is not far from the canonical value of 100, however. In ρ Oph A, the exponent β of the power-law description for the dust opacity exhibits a clear dependence on time, with high values of 2 for the envelope-dominated emission in starless Class -1 sources to low values close to 0 for the disk-dominated emission in Class III objects. β assumes intermediate values for evolutionary classes in between. Conclusions. Since β is primarily controlled by grain size, grain growth mostly occurs in circumstellar disks. The spatial segregation of gas and dust, seen in projection toward the core centre, probably implies that, like C¹⁸O, also N<inf>2</inf>H⁺ is frozen onto the grains

Gravitational Radiation Detection

This dissertation studies resonant gravitational wave detectors and related data analysis. Different forms (strain amplitude) of the equation of motion for a medium responding to a gravitational wave are discussed in relation to the detection of such waves. Utilizing "Bayesian techniques" an optimal method for data analysis is developed. Noise and filter theory is reviewed. It is seen that the “Bayesian techniques" integrates filter theory and data analysis, providing both filter properties and optimal methods for integrating the data.(In particular the method leads to a non threshold type of analysis, and "looks for" correlation between two detectors without the use of time delay). Expressions for optimal sensitivity (and filters) of detector systems are given, including the limit of perfect sensors and electronics. The signal to noise ratio in terms of the spectral power of the gravitational radiation is derived. Long baseline interferometry is discussed. A computer program simulating a pair of Weber type detectors is developed to study different approaches to data analysis

Molecular gas in the galaxy M 83 II . Kinematics of the molecular gas

We present the kinematics of the molecular gas in the barred spiral galaxy M83 (NGC5236). The study is based on ^{12}CO(J=1--0 and 2--1) observations with the Swedish-ESO Submillimetre Telescope (SEST). Iso-velocity maps of the entire optical disk, 10'x10' or 13x13 kpc, are produced. They show the pattern of an inclined, rotating disk, but also the effects of streaming motions along the spiral arms. A dynamical mass of about 6x10^10 M_sun is estimated by fitting the rotation curve of an exponential disk model to these data. The gas constitutes about 13% of the disk mass. The pattern speed is determined from the residual velocity pattern The locations of various resonances are discussed. The molecular gas velocity dispersion is determined, and a trend of decreasing dispersion with increasing galactocentric radius is found. A total gas (H_2+HI+He) mass surface density map is presented, and compared to the critical density for star formation of an isothermal gaseous disk. The critical density is exceeded in the spiral arms, but not in the interarm regions. The locations of Giant Molecular Associations (GMAs) and HII regions are consistent with this scenario of dynamically induced star formation.Comment: 19 pages, 14 figures, A&A submitted. A higher resolution version available at http://www.astro.su.se/~andreas/publications