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alg-geom/9301001
Lines on Calabi Yau complete intersections, mirror symmetry, and Picard Fuchs equations
A relation between the number of rational curves of fixed degree on Calabi Yau threefolds and the Picard Fuchs equations, which was suggested as part of the study of mirror symmetry, is verified in the case of complete intersection of two cubics and lines.
1993-01-04
2008-02-03
[ "alg-geom", "math.AG" ]
A.Libgober and J.Teitelbaum
astro-ph/9312065
Inhomogeneous Primordial Nucleosynthesis: Coupled Nuclear Reactions and Hydrodynamic Dissipation Processes
We present a detailed study of inhomogeneous Big Bang nucleosynthesis where, for the first time, nuclear reactions are coupled to all significant fluctuation dissipation processes. Theses processes include neutrino heat transport, baryon diffusion, photon diffusive heat transport, and hydrodynamic expansion with photon...
1993-12-30
2009-10-22
[ "astro-ph" ]
K. Jedamzik, G.M. Fuller, and G.J. Mathews
astro-ph/9312066
Enhanced Heavy-Element Formation in Baryon-Inhomogeneous Big-Bang Models
We show that primordial nucleosynthesis in baryon inhomogeneous big-bang models can lead to significant heavy-element production while still satisfying all the light-element abundance constraints including the low lithium abundance observed in population II stars. The parameters which admit this solution arise naturall...
1993-12-30
2009-10-22
[ "astro-ph" ]
K. Jedamzik, G.M. Fuller, G.J. Mathews, and T. Kajino
astro-ph/9312064
Can Conformal Weyl Gravity be Considered a Viable Cosmological Theory?
We present exact analytical solutions to the Conformal Weyl Gravity cosmological equations that are valid for both the matter and radiation dominated eras. The Primordial Nucleosynthesis process is also exhaustively studied. The main conclusion of our work is that cosmological models derived from this theory are not li...
1993-12-29
2009-10-22
[ "astro-ph" ]
D. Elizondo and G. Yepes
astro-ph/9312063
The Evolution of Non-Linear Sub-Horizon Scale Entropy Fluctuations in the Earlu Universe
We examine the damping of non-linear sub-horizon scale entropy fluctuations in early epochs of the universe ($T\approx 100$ GeV to $T\approx 1$keV) by neutrino, baryon, and photon induced dissipative processes. Results of numerical evolution calculations are presented for broad ranges of initial fluctuation amplitudes ...
1993-12-28
2009-10-22
[ "astro-ph" ]
K. Jedamzik and G.M. Fuller
astro-ph/9312062
Primordial Nucleosynthesis with a Decaying Tau Neutrino
A comprehensive study of the effect of an unstable tau neutrino on primordial nucleosynthesis is presented. The standard code for nucleosynthesis is modified to allow for a massive decaying tau neutrino whose daughter products include neutrinos, photons, $e^\pm$ pairs, and/or noninteracting (sterile) daughter products....
1993-12-28
2008-11-26
[ "astro-ph", "hep-ph" ]
S. Dodelson, G. Gyuk, and M.S. Turner
astro-ph/9312061
Glitches in the X-Ray Pulsar 1e 2259+586
Starquakes are considered for fast-rotating magnetic white dwarfs. The X-ray pulsar 1E 2259 + 586 may be such a white dwarf. It is shown that in this case starquakes may be responsible for the decrease of the mean spin-down rate which was observed for 1E 2259 + 586 between 1987 and 1990. The required mass of the white ...
1993-12-27
2009-10-22
[ "astro-ph" ]
Vladimir V. Usov
astro-ph/9312059
Gravitational Microlensing by the MACHOs of the LMC
The expected microlensing events of the LMC by the MACHOs of the LMC itself are calculated and compared with analogue events by objects in the Galactic halo. The LMC matter distribution is modelled by a spherical halo and an exponential disk while a face-on exponential disk is used for the stellar distribution of the L...
1993-12-24
2009-10-22
[ "astro-ph" ]
Xiang-Ping Wu
astro-ph/9312060
Galaxy-cluster associations from gravitational lensing
We investigate the associations between background galaxies and foreground clusters of galaxies due to the effect of gravitational lensing by clusters of galaxies. Similar to the well-known quasar-galaxy ones, these associations depend sensitively on the shape of galaxy number-magnitude or number-flux relation, and bot...
1993-12-24
2011-05-23
[ "astro-ph" ]
Xiang-Ping Wu and Francois Hammer
astro-ph/9312058
A further discussion on quasar-galaxy associations from gravitational lensing
Quasar-galaxy associations, if they result from the effect of gravitational lensing by foreground galaxies, depend sensitively on the shape of the quasar number counts. Two kinds of quasar number-magnitude relations are predicted to produce quite different properties in quasar-galaxy associations: the counts of Boyle, ...
1993-12-24
2011-05-23
[ "astro-ph" ]
Xiang-Ping Wu
astro-ph/9312057
Anisotropies of Cosmic Background Radiation from a Local Collapse
We present an exact solution of the anisotropies of cosmic background radiation (CBR) from a local collapse described by a spherical over-dense region embedded in a flat universe, with the emphasis on the relationship between the dipole $(\Delta {\sf T}/{\sf T})_d$ and the quadrupole $(\Delta {\sf T}/{\sf T})_q$ anisot...
1993-12-24
2009-10-22
[ "astro-ph" ]
Xiang-Ping Wu and Li-Zhi Fang
astro-ph/9312056
Dipole Anisotropy in the COBE DMR First-Year Sky Maps
We present a determination of the cosmic microwave background dipole amplitude and direction from the COBE Differential Microwave Radiometers (DMR) first year of data. Data from the six DMR channels are consistent with a Doppler-shifted Planck function of dipole amplitude Delta T = 3.365 +/-0.027 mK toward direction (l...
1993-12-23
2009-10-22
[ "astro-ph" ]
A. Kogut, C. Lineweaver, G.F. Smoot, C. L. Bennett, A. Banday, et al
astro-ph/9312054
The Role of Chaos in the Circularization of Tidal Capture Binaries. II. Long-Term Evolution
A self-consistent, adiabatic model for the {\it long-time} behaviour of tidal capture binaries is presented. It is shown that most capture orbits behave chaotically, with the eccentricity following a quasi-random walk between the values of $\appless 1$ and some lower limit associated with the periastron separation at c...
1993-12-22
2007-05-23
[ "astro-ph" ]
Rosemary A. Mardling, (Monash, Australia)
astro-ph/9312055
The Variance of QSO Counts in Cells
{}From three quasar samples with a total of 1038 objects in the redshift range $1.0 \div 2.2$ we measure the variance $\sigma^2$ of counts in cells of volume $V_u$. By a maximum likelihood analysis applied separately on these samples we obtain estimates of $\sigma^2(\ell)$, with $\ell \equiv V_u^{1/3}$. The analysis fr...
1993-12-22
2009-10-22
[ "astro-ph" ]
P. Andreani, S. Cristiani, F. Lucchin, S. Matarrese and L. Moscardini
astro-ph/9312053
The Role of Chaos in the Circularization of Tidal Capture Binaries. I. the Chaos Boundary
A self-consistent model for binary evolution devised by Gingold \& Monaghan (1980) is used to show that two distinctly different types of behaviour are possible for close eccentric binaries. The model is based on a linear adiabatic normal mode analysis of the problem, which allows detailed examination of the transfer o...
1993-12-22
2007-05-23
[ "astro-ph" ]
Rosemary A. Mardling, (Monash, Australia)
astro-ph/9312049
Detection of Signature Consistent with Cosmological Time Dilation in Gamma-Ray Bursts
If gamma-ray bursters are at cosmological distances - as suggested by their isotropic distribution on the sky and by their number-intensity relation - then the burst profiles will be stretched in time, by an amount proportional to the redshift, 1 + $z$. We have tested data from the {\it Compton} Gamma Ray Observatory's...
1993-12-21
2009-10-22
[ "astro-ph" ]
J. P. Norris (NASA/GSFC), R. J. Nemiroff (NASA/GMU), J. D. Scargle (NASA/AMES), C. Kouveliotou (NASA/USRA), G. J. Fishman (NASA/MSFC), C. A. Meegan (NASA/MSFC), W. S. Paciesas (NASA/UAH), J. T. Bonnell (NASA/CSC)
astro-ph/9312051
Synthetic metal line indices for elliptical galaxies from super metal rich alpha-enhanced stellar models
There are strong indications from recent papers (e.g. Worthey et al. 1992) that the abundance ratio of Mg/Fe, and consequently also O/Fe in giant elliptical galaxies is not solar. The line strengths of two Fe lines at 5270 and 5335 A are weaker than one expects from the strength of the Mg b line if [Mg/Fe] = 0. We have...
1993-12-21
2007-05-23
[ "astro-ph" ]
A. Weiss, R.F. Peletier and F. Matteucci
astro-ph/9312050
On the Mass of the Dark Compact Halo Objects
Recently the French EROS collaboration and the American-Australian MACHO collaboration have reported the observation of altogether three possible microlensing events by monitoring over several years the brightness of millions of stars in the Large Magellanic Cloud. For each of these events, assuming they are due to mic...
1993-12-21
2009-10-22
[ "astro-ph" ]
Philippe Jetzer and Eduard Masso (Zurich Univ.)
astro-ph/9312052
On the Location of the Acceleration and Emission Sites in Gamma-Ray Blazars
Compton scattering of external radiation by nonthermal particles in outflowing blazar jets is dominated by accretion-disk photons rather than scattered radiation to distances $\sim 0.01-0.1$ pc from the central engine for standard parameters, thus clarifying the limits of validity of the model by the present authors an...
1993-12-21
2007-05-23
[ "astro-ph" ]
Charles D. Dermer and Reinhard Schlickeiser
astro-ph/9312048
Radiation from Vela-Like Pulsars Near the Death Line
Radiation of both the outer gaps and the neutron star surface is considered for a Vela-like pulsar near the death line. It is shown that if such a pulsar is close enough to the death line, its optical, UV and X-ray emission has to increase. Using results of this consideration, it is argued that Geminga is not a close r...
1993-12-20
2009-10-22
[ "astro-ph" ]
Vladimir V. Usov
astro-ph/9312047
Can EROS/MACHO be detecting the galactic spheroid instead of the galactic halo?
Models of our galaxy based on dynamical observations predict a spheroid component much heavier than accounted for by direct measurements of star counts and high velocity stars. If, as first suggested by Caldwell and Ostriker, this discrepancy is due to a large population of faint low-mass stars or dark objects in the s...
1993-12-19
2010-11-30
[ "astro-ph", "hep-ph" ]
G.F. Giudice, S. Mollerach, and E. Roulet
astro-ph/9312046
The Very-Soft X-Ray Emission of X-Ray Faint Early-Type Galaxies
A recent re-analysis of Einstein data, and new ROSAT observations, have revealed the presence of at least two components in the X-ray spectra of X-ray faint early-type galaxies: a relatively hard component (kT>1.5 keV), and a very soft component (kT\sim 0.2-0.3 keV). We address the problem of the nature of the very sof...
1993-12-19
2010-12-13
[ "astro-ph" ]
S.Pellegrini and G. Fabbiano
astro-ph/9312045
Very High Energy Gamma-Rays from AGN: Cascading on the Cosmic Background Radiation Fields and the Formation of Pair Halos
Recent high energy gamma-ray observations (E>100 MeV) of blazar AGN show emission spectra with no clear upper energy cutoff. AGN, considered to be possible sources for the highest energy cosmic rays, may have emission extending well into the VHE (very high energy, E>100 GeV) domain. Because VHE gamma-rays are absorbed ...
1993-12-18
2019-08-17
[ "astro-ph" ]
F.A. Aharonian, P.S. Coppi, H.J. Voelk
astro-ph/9312044
Optimizing the Zel'dovich Approximation
We have recently learned that the Zeldovich approximation can be successfully used for a far wider range of gravitational instability scenarios than formerly proposed; we study here how to extend this range. In previous work we studied the accuracy of several analytic approximations to gravitational clustering in the m...
1993-12-18
2015-06-24
[ "astro-ph" ]
A.L. Melott, T.F. Pellman, and S.F. Shandarin
astro-ph/9312042
Spectroscopy of Dwarf Elliptical Galaxies in the Fornax Cluster
We present the results of spectroscopic observations of 10 nucleated dwarf elliptical galaxies (dE's) in the Fornax cluster. The blue spectra of Fornax dE galaxies indicate a wide range of metallicities at a given luminosity, similar to those of intermediate to \it metal-rich globular clusters. Metal abundances derived...
1993-12-17
2009-10-22
[ "astro-ph" ]
Enrico V. Held and Jeremy R. Mould
astro-ph/9312041
CO Observations of Edge-on Galaxies, V. NGC 5907: Central Deficiency of Gas in an Sc Galaxy - Merger in the Bulge
The edge-on Sc galaxy NGC 5907 has been observed in the 12CO(1-0)-line emission using the Nobeyama 45-m telescope. The radial density distribution between 2 and 13 kpc is well represented by a superposition of an exponential-law disk of scale radius 3.5 kpc and a ring of 7 kpc radius. However, no concentration of gas h...
1993-12-17
2007-05-23
[ "astro-ph" ]
Yoshiaki SOFUE
astro-ph/9312040
Anisotropy in the Angular Broadening of Sgr A$^*$ at the Galactic Center
We present the results of a $\lambda$20 cm VLA observation of the compact Galactic center radio source Sgr A$^*$. The scatter-broadened image is elongated in the East-West direction, with an axial ratio of 0.6$\pm$0.05 and a position angle of 87$^0\pm$3$^0$. A similar shape and orientation has been found previously at ...
1993-12-17
2007-05-23
[ "astro-ph" ]
F. Yusef-Zadeh W. Cotton M. Wardle F. Melia and D. Roberts
astro-ph/9312043
Can MACHOs Probe the Shape of the Galaxy Halo?
We study the prospects for the current microlensing searches, which have recently discovered several candidates, to yield useful information about the flattening of the Galaxy dark matter halo. Models of HI warps and N-body simulations of galaxy formation suggest that disks commonly form in oblate halos with a tilt bet...
1993-12-17
2009-10-22
[ "astro-ph" ]
Joshua A. Frieman and Rom\'an Scoccimarro
astro-ph/9312038
Theoretical Expectations for Bulk Flows in Large Scale Surveys
We calculate the theoretical expectation for the bulk motion of a large scale survey of the type recently carried out by Lauer and Postman. Included are the effects of survey geometry, errors in the distance measurements, clustering properties of the sample, and different assumed power spectra. We consider the power sp...
1993-12-16
2009-10-22
[ "astro-ph" ]
Hume A. Feldman and Richard Watkins
astro-ph/9312035
On Identifying the Present-Day Vacuum Energy with the Potential Driving Inflation
There exists a growing body of observational evidence supporting a non-vanishing cosmological constant at the present epoch. We examine the possibility that such a term may arise directly from the potential energy which drove an inflationary expansion of the very early universe. To avoid arbitrary alterations in the sh...
1993-12-16
2014-10-13
[ "astro-ph" ]
Richard A. Frewin and James E. Lidsey
astro-ph/9312036
Groups and Clusters in the Near-Infrared
Massive multicolor digital surveys in the near infrared provide new opportunities for statistical analyses of the properties of groups and clusters. These galaxy systems provide a natural laboratory for studying dynamical processes and galaxy evolution, and serve as powerful cosmological diagnostics. The immediate scie...
1993-12-16
2009-10-22
[ "astro-ph" ]
Gary A. Mamon (DAEC, Obs. de Meudon & IAP)
astro-ph/9312037
Tilting the Primordial Power Spectrum with Bulk Viscosity
Within the context of the cold dark matter model, current observations suggest that inflationary models which generate a tilted primordial power spectrum with negligible gravitational waves provide the most promising mechanism for explaining large scale clustering. The general form of the inflationary potential which p...
1993-12-16
2015-06-24
[ "astro-ph" ]
James E. Lidsey
astro-ph/9312039
Fluctuations of the Gravitational Constant in the Inflationary Brans-Dicke Cosmology
According to the Brans--Dicke theory, the value of the gravitational constant G which we measure at present is determined by the value of the Brans--Dicke scalar field \phi at the end of inflation. However, due to quantum fluctuations of the scalar fields produced during inflation, the gravitational constant G(\phi) ma...
1993-12-16
2009-09-29
[ "astro-ph", "gr-qc", "hep-th" ]
Juan Garcia-Bellido, Andrei Linde and Dmitri Linde
astro-ph/9312032
Orbital Variability in the Eclipsing Pulsar Binary PSR B1957+20
We have conducted timing observations of the eclipsing millisecond binary pulsar PSR~B1957+20, extending the span of data on this pulsar to more than five years. During this time the orbital period of the system has varied by roughly $\Delta P_b/P_b = 1.6 \times 10^{-7}$, changing quadratically with time and displaying...
1993-12-15
2009-10-22
[ "astro-ph" ]
Z. Arzoumanian (Princeton), A. S. Fruchter (STScI), J. H. Taylor (Princeton)
astro-ph/9312033
The Three--Point Correlation Function of the Cosmic Microwave Background in Inflationary Models
We analyze the temperature three--point correlation function and the skewness of the Cosmic Microwave Background (CMB), providing general relations in terms of multipole coefficients. We then focus on applications to large angular scale anisotropies, such as those measured by the {\em COBE} DMR, calculating the contrib...
1993-12-15
2009-10-22
[ "astro-ph" ]
A.Gangui, F.Lucchin, S.Matarrese and S.Mollerach
astro-ph/9312034
Low Frequency Spectra of Gamma-Ray Bursts
Particles with energies below the mean energy $E_0$ in relativistic shocked plasmas should assume an equilibrium energy distribution. This leads to a synchrotron spectrum $F_\nu \propto \nu^{1/3}$ up to approximately the critical frequency $\nu_0$ of an electron with the energy $E_0$. Application to GRBs implies that a...
1993-12-15
2011-03-17
[ "astro-ph" ]
J. I. Katz
astro-ph/9312030
Stellar Content and Star Formation Histories
The evolution of irregular galaxies is examined from two points of view: on the one hand, models of galactic chemical evolution have been computed and their predictions compared with the corresponding observational data on the element abundances, and on the other hand, the results of a new method to derive the star for...
1993-12-14
2007-05-23
[ "astro-ph" ]
M.Tosi
astro-ph/9312029
Preliminary Results from the ESO Slice Project (ESP)
We present the first results of a galaxy redshift survey, ESO Slice Project (ESP), we are accomplishing as an ESO Key--Project over about 40 square degrees in a region near the South Galactic Pole. The limiting magnitude is $b_J = 19.4$. Up to now $\sim 85\%$ of the observations has been completed and $\sim 65\%$ of th...
1993-12-14
2007-05-23
[ "astro-ph" ]
G.Vettolani, E.Zucca, A.Cappi, R.Merighi, M.Mignoli, G.Stirpe, G.Zamorani, C.Collins, H.MacGillivray, C.Balkowski, J.Alimi, A.Blanchard, V.Cayatte, P.Felenbok, S.Maurogordato, D.Proust, G.Chincarini, L.Guzzo, D.Maccagni, R.Scaramella, M.Ramella
astro-ph/9312031
Statistics and Topology of the COBE DMR First Year Maps
We use statistical and topological quantities to test the COBE-DMR first year sky maps against the hypothesis that the observed temperature fluctuations reflect Gaussian initial density perturbations with random phases. Recent papers discuss specific quantities as discriminators between Gaussian and non-Gaussian behavi...
1993-12-14
2011-02-11
[ "astro-ph" ]
G.F. Smoot, L. Tenorio, A.J. Banday, A. Kogut, E.L. Wright, G. Hinshaw, and C. Bennett
astro-ph/9312028
Robust Morphological Measures for Large-Scale Structure in the Universe
We propose a novel method for the description of spatial patterns formed by a coverage of point sets representing galaxy samples. This method is based on a complete family of morphological measures known as Minkowski functionals, which includes the topological Euler characteristic and geometric descriptors to specify t...
1993-12-14
2007-05-23
[ "astro-ph" ]
K.R. Mecke, T. Buchert, H. Wagner
astro-ph/9312026
Skewness and Kurtosis in Large-Scale Cosmic Fields
In this paper, I present the calculation of the third and fourth moments of both the distribution function of the large--scale density and the large--scale divergence of the velocity field, $\theta$. These calculations are made by the mean of perturbative calculations assuming Gaussian initial conditions and are expect...
1993-12-13
2009-10-22
[ "astro-ph" ]
F. Bernardeau
astro-ph/9312025
Shock Excited Maser Emission from the Supernova Remnant W28
We present VLA observations in the hydroxyl line OH(1720 MHz) towards the supernova remnant W28. These high resolution images show a more extensive distribution of 1720 MHz emission than had previously been suspected from earlier single-dish observations. A total of 26 distinct maser spots were detected which lie on th...
1993-12-13
2009-10-22
[ "astro-ph" ]
D. A. Frail, W. M. Goss and V. I. Slysh
astro-ph/9312027
The Effect of Repeating Gamma Ray Bursts on V/Vmax
I consider the effect of repeating gamma ray burst sources on the <V/Vmax> statistic. I find that the treatment of repeating events, if applied consistently, will not affect the effectiveness of <V/Vmax> as a test of burst homogeneity. The calculation of <V/Vmax> for apparent repeating and nonrepeating source populatio...
1993-12-13
2009-10-22
[ "astro-ph" ]
David Band
astro-ph/9312024
On the Nature of Nonthermal Radiation from Cosmological Gamma-Ray Bursters
Relativistic electron-positron winds with strong magnetic fields are considered as a source of radiation for cosmological $\gamma$-ray bursters. Such a wind is generated by a millisecond pulsar with a very strong magnetic field. An electron-positron plasma near the pulsar is optically thick and in quasi-thermodynamic e...
1993-12-13
2015-06-24
[ "astro-ph" ]
Vladimir V. Usov
astro-ph/9312023
A Possible Local Counterpart to the Excess Population of Faint Blue Galaxies
OBSERVATIONS of galaxies to very faint magnitudes have revealed a population of blue galaxies at intermediate redshift$^{1-5}$. These galaxies represent a significant excess over the expectation of standard cosmological models for reasonable amounts of evolution of the locally observed galaxy population. However, the s...
1993-12-12
2009-10-22
[ "astro-ph" ]
Stacy McGaugh
astro-ph/9312022
Introduction to Cosmology
These notes form an introduction to cosmology with special emphasis on large scale structure, the cmb anisotropy and inflation. In some places a basic familiarity with particle physics is assumed, but otherwise no special knowledge is needed. Most of the material in the first two sections can be found in several texts,...
1993-12-12
2007-05-23
[ "astro-ph", "gr-qc", "hep-ph" ]
David H Lyth (School of Physics and Materials, Lancaster University, 52 LA1 4YB. U. K.)
astro-ph/9312021
Mass and radius of cosmic balloons
This revised version uses Gauss-Codazzi equations to derive the exact mass and radius relations. The results remain qualitatively the same.
1993-12-11
2009-10-22
[ "astro-ph", "hep-ph" ]
Yun Wang
astro-ph/9312018
Gravothermal Oscillations
Gravothermal oscillations occur in several models for the post-collapse evolution of rich star clusters. This paper reviews the main literature, and presents some new N-body results which appear to exhibit this phenomenon.
1993-12-10
2007-05-23
[ "astro-ph" ]
Douglas C. Heggie (University of Edinburgh, Department of Mathematics and Statistics,King's Buildings,Edinburgh EH10 5NL,U.K.)
astro-ph/9312019
A Self-Consistent Approach to Neutral-Current Processes in Supernova Cores
The problem of neutral-current processes (neutrino scattering, pair emission, pair absorption, axion emission, \etc) in a nuclear medium can be separated into an expression representing the phase space of the weakly interacting probe, and a set of dynamic structure functions of the medium. For a non-relativistic medium...
1993-12-10
2011-05-12
[ "astro-ph", "hep-ph" ]
Georg Raffelt and David Seckel
astro-ph/9312020
Mixed Dark Matter from Neutrino Lasing
We investigate the production of dark matter with non-standard momentum distributions arising from the decay of a relativistic massive neutrino into a lighter fermion and boson H$\rightarrow$F$+$B. We develop the Boltzmann equations for this process, paying particular attention to spin polarisation effects. Such decays...
1993-12-10
2009-10-22
[ "astro-ph", "hep-ph" ]
G.D. Starkman, N. Kaiser, R.A. Malaney
astro-ph/9312016
The Baryonic Fraction in Groups of Galaxies from X-Ray Measurements
The recent {\sl ROSAT \/} X-ray detections of hot intergalactic gas in three groups of galaxies are reviewed and the resulting baryonic fraction in these groups is reevaluated. We show that the baryonic fraction obtained, assuming hydrostatic equilibrium, should depend, perhaps sensitively, on the radius out to which t...
1993-12-08
2009-10-22
[ "astro-ph" ]
Mark J. Henriksen (U. of Alabama) and Gary A. Mamon (DAEC, Obs. de Meudon)
astro-ph/9312017
Large-Angle Cosmic Microwave Background Anisotropies in an Open Universe
If the Universe is open, scales larger than the curvature scale may be probed by large-angle fluctuations in the cosmic microwave background (CMB). We consider primordial adiabatic perturbations and discuss power spectra that are power laws in volume, wavelength, and eigenvalue of the Laplace operator. The resulting la...
1993-12-08
2008-11-26
[ "astro-ph", "hep-ph" ]
Marc Kamionkowski and David N. Spergel
astro-ph/9312015
Using FU Orionis Outbursts to Constrain Self-Regulated Protostellar Disk Models
One dimensional, convective, vertical structure models and one dimensional, time dependent, radial diffusion models are combined to create a self-consistent picture in which FU~Orionis outbursts occur in young stellar objects (YSOs) as the result of a large scale, self-regulated, thermal ionization instability in the s...
1993-12-08
2009-10-22
[ "astro-ph" ]
K. R. Bell and D. N. C. Lin
astro-ph/9312014
Decaying Neutrinos in Galaxy Clusters
Davidsen et al. (1991) have argued that the failure to detect uv photons from the dark matter DM) in cluster A665 excludes the decaying neutrino hypothesis. Sciama et al. (1993) argued that because of high central concentration the DM in that cluster must be baryonic. We study the DM profile in clusters of galaxies sim...
1993-12-07
2010-11-30
[ "astro-ph" ]
Adrian L. Melott, Randall J. Splinter, Massimo Persic and Paolo Salucci
astro-ph/9312013
Position Angles and Alignments of Galaxy Clusters
The position angles of a large number of Abell and Shectman clusters (in total 637 clusters), identified in the Lick map as surface density enhancements, are estimated. Using published redshifts for 277 of these I have detected strong nearest neighbour alignments (2.5 - 3 sigma level), up to about 15 Mpc (Ho = 100). We...
1993-12-07
2007-05-23
[ "astro-ph" ]
Manolis Plionis (SISSA, via Beirut 2-4, Trieste 34013, Italy)
astro-ph/9312012
Quantum Noise in Gravitation and Cosmology
We begin by enumerating the many processes in gravitation and cosmology where quantum noise and fluctuations play an active role such as particle creation, galaxy formation and entropy generation. Using the influence functional we first explain the origin and nature of noise in quantum systems interacting with an envir...
1993-12-07
2007-05-23
[ "astro-ph", "gr-qc" ]
Bei-lok Hu and Andrew Matacz
astro-ph/9312011
Dark Matter Annihilations in the Large Magellanic Cloud
The flat rotation curve obtained for the outer star clusters of the Large Magellanic Cloud is suggestive of an LMC dark matter halo. From the composite HI and star cluster rotation curve, I estimate the parameters of an isothermal dark matter halo added to a `maximum disk.' I then examine the possibility of detecting h...
1993-12-06
2009-10-22
[ "astro-ph" ]
P Gondolo
astro-ph/9312010
The formation of disk galaxies in a cosmological context: Populations, metallicities and metallicity gradients
We present first results concerning the metallicities and stellar populations of galaxies formed in a cosmologically motivated simulation. The calculations include dark matter, gas dynamics, radiation processes, star formation, supernovae feedback, and metal enrichment. A rotating, overdense sphere with a mass of $8\,1...
1993-12-05
2007-05-23
[ "astro-ph" ]
Matthias Steinmetz & Ewald Mueller
astro-ph/9312009
Microlensing of Unresolved Stars as a Brown Dwarf Detection Method
We describe a project of brown dwarf detection in the dark halo of a galaxy using the microlensing effect. We argue that monitoring pixels instead of stars could provide an enhancement in the number of detectable events. We estimate the detection efficiency with a Monte-Carlo simulation. We expect a ten-fold increase w...
1993-12-05
2009-09-25
[ "astro-ph" ]
Alain Bouquet, Jean Kaplan, Anne-Laure Melchior, Yannick Giraud-H\'eraud, Paul Baillon
astro-ph/9312008
Halo Cold Dark Matter and Microlensing
There is good evidence that most of the baryons in the Universe are dark and some evidence that most of the matter in the Universe is nonbaryonic with cold dark matter (cdm) being a promising possibility. We discuss expectations for the abundance of baryons and cdm in the halo of our galaxy and locally. We show that in...
1993-12-04
2009-10-22
[ "astro-ph", "hep-ph" ]
Evalyn Gates and Michael S. Turner
astro-ph/9312004
The Angular Bispectrum of The Cosmic Microwave Background
COBE has provided us with a whole-sky map of the CBR anisotropies. However, even if the noise level is negligible when the four year COBE data are available, the cosmic variance will prevent us from obtaining information about the Gaussian nature of the primordial fluctuations. This important issue is addressed here by...
1993-12-03
2016-08-30
[ "astro-ph" ]
Xiaochun Luo
astro-ph/9312005
Cluster Correlations in the Zel'dovich Approximation
We show how to simulate the clustering of rich clusters of galaxies using a technique based on the Zel'dovich approximation. This method well reproduces the spatial distribution of clusters obtainable from full N-body simulations at a fraction of the computational cost. We use an ensemble of large--scale simulations to...
1993-12-03
2015-06-24
[ "astro-ph" ]
S. Borgani, P. Coles, L. Moscardini
astro-ph/9312007
Perturbation Theory Confronts Observations~: Implications for the ``Initial'' Conditions and Omega
This paper covers the material of our two talks. We describe a series of projects based upon perturbative expansions to follow the gravitational evolution of the one point probability distribution functions (PDFs) for the density contrast field and for the divergence of the corresponding velocity field. The Edgeworth e...
1993-12-03
2007-05-23
[ "astro-ph" ]
F. R. Bouchet and R. Juszkiewicz
astro-ph/9312006
The Time Development of a Resonance Line in the Expanding Universe
The time-dependent spectral profile of a resonance line in a homogeneous expanding medium is studied by numerically solving an improved Fokker-Planck diffusion equation. The solutions are used to determine the time required to reach a quasi-static solution near the line center. A simple scaling law for this relaxation ...
1993-12-03
2009-10-22
[ "astro-ph" ]
George B. Rybicki, and Ian P. Dell'Antonio
astro-ph/9312002
Solar Neutrinos: What We Have Learned
The four operating solar neutrino experiments confirm the hypothesis that the energy source for solar luminosity is hydrogen fusion. However, the measured rate for each of the four solar neutrino experiments differs significantly (by factors of 2.0 to 3.5) from the corresponding theoretical prediction that is based upo...
1993-12-02
2015-06-24
[ "astro-ph" ]
John N. Bahcall
astro-ph/9312003
Visual Distortions Near a Neutron Star and Black Hole
The visual distortion effects visible to an observer traveling around and descending to the surface of an extremely compact star are described. Specifically, trips to a ``normal" neutron star, a black hole, and an ultracompact neutron star with extremely high surface gravity, are described. Concepts such as multiple im...
1993-12-02
2008-11-26
[ "astro-ph", "gr-qc" ]
Robert J. Nemiroff (NASA/GSFC and George Mason University)
astro-ph/9312001
Galaxy Groups in Cold + Hot and CDM Universes: Comparison with CfA
This letter presents results of new high resolution $\Omega=1$ Cold + Hot Dark Matter (CHDM) and Cold Dark Matter (CDM) simulations. Properties of groups in these simulations reflect the lower small-scale velocities and the greater tendency to form distinct filaments on both small and large scales in CHDM as compared t...
1993-12-01
2009-10-22
[ "astro-ph" ]
Richard Nolthenius, Anatoly Klypin, and Joel R. Primack
astro-ph/9311076
Quantitative Analysis of Voids in Percolating Structures in Two-Dimensional N-Body Simulations
We present in this paper a quantitative method for defining void size in large-scale structure based on percolation threshold density. Beginning with two-dimensional gravitational clustering simulations smoothed to the threshold of nonlinearity, we perform percolation analysis to determine the large scale structure. Th...
1993-11-30
2008-02-03
[ "astro-ph" ]
P.M. Harrington, A.L. Melott, and S.F. Shandarin
astro-ph/9311074
Arc Statistics with Realistic Cluster Potentials. I. Method and First Results
{}From the lensing properties of a numerically simulated cluster, from the statistical properties of the giant arcs produced by the cluster, and from comparing the cluster properties derived both from lensing and from the X-ray properties of the intracluster gas, we conclude (1) that clusters may be significantly more ...
1993-11-30
2007-05-23
[ "astro-ph" ]
M. Bartelmann and A.Weiss
astro-ph/9311077
The Gravitational Lens System B1422$+$231: Dark Matter, Superluminal Expansion and the Hubble Constant
A gravitational lens model of the radio quasar B1422+231 is presented which can account for the image arrangement and approximately for the relative magnifications. The locations of the principal lensing mass and a more distant secondary mass concentration were predicted and subsequently luminous galaxies were found at...
1993-11-30
2015-06-24
[ "astro-ph" ]
David W. Hogg & R. D. Blandford
astro-ph/9311075
A Test of the Adhesion Approximation for Gravitational Clustering
We quantitatively compare a particle implementation of the adhesion approximation to fully non--linear, numerical nbody simulations. Our primary tool, cross--correlation of nbody simulations with the adhesion approximation, indicates good agreement, better than that found by the same test performed with the Zel'dovich ...
1993-11-30
2009-10-22
[ "astro-ph" ]
A.L. Melott, S.F. Shandarin, and D.H. Weinberg
astro-ph/9311073
Geometrical Evidence for Dark Matter: X-ray Constraints on the Mass of the Elliptical Galaxy NGC 720
(shortened for babbage) We describe (1) a new test for dark matter and alternate theories of gravitation based on the relative geometries of the X-ray and optical surface brightness distributions and an assumed form for the potential of the optical light, (2) a technique to measure the shapes of the total gravitating m...
1993-11-29
2008-11-26
[ "astro-ph" ]
D. A. Buote & C. R. Canizares
astro-ph/9311071
Spectral Properties of Blast Wave Models of Gamma-Ray Burst Sources
We calculate the spectrum of blast wave models of gamma-ray burst sources, for various assumptions about the magnetic field density and the relativistic particle acceleration efficiency. For a range of physically plausible models we find that the radiation efficiency is high, and leads to nonthermal spectra with breaks...
1993-11-29
2011-09-30
[ "astro-ph" ]
P. Meszaros, M.J.Rees and H.Papathanassiou
astro-ph/9311070
Second Order Power Spectrum and Nonlinear Evolution at High Redshift
The Eulerian cosmological fluid equations are used to study the nonlinear mode coupling of density fluctuations. We evaluate the second-order power spectrum including all four-point contributions. In the weakly nonlinear regime we find that the dominant nonlinear contribution for realistic cosmological spectra is made ...
1993-11-29
2009-10-22
[ "astro-ph" ]
Bhuvnesh Jain and Edmund Bertschinger
astro-ph/9311072
Amplitude of Primeval Fluctuations from Cosmological Mass Density Reconstructions
We use the POTENT reconstruction of the mass density field in the nearby universe to estimate the amplitude of the density fluctuation power spectrum for various cosmological models. We find sigma_8\Omega_m^{0.6}= 1.3^{+0.4}_{-0.3}, almost independently of the power spectrum. This value agrees well with the COBE normal...
1993-11-29
2009-10-22
[ "astro-ph" ]
Uros Seljak and Edmund Bertschinger
astro-ph/9311069
Cosmic Structure Formation
This article reviews the prevailing paradigm for how galaxies and larger structures formed in the universe: gravitational instability. Basic observational facts are summarized to motivate the standard cosmological framework underlying most detailed investigations of structure formation. The observed universe approaches...
1993-11-29
2009-10-22
[ "astro-ph", "chao-dyn", "nlin.CD" ]
Edmund Bertschinger
astro-ph/9311068
The power spectrum implied by COBE and the matter correlation function
A phenomenological power spectrum of primordial density perturbations has been constructed by using both COBE data to probe the large wavelength region, and a double power law, locally deduced from galaxy catalogs, which describes the matter correlation function up to tens of Megaparsec. The shape of the spectrum P(k) ...
1993-11-28
2008-02-03
[ "astro-ph" ]
S. Torres, R. Fabbri, R. Ruffini
astro-ph/9311067
Topological Analysis of COBE-DMR CMB Maps
Geometric characteristics of random fields are exploited to test the consistency of density perturbation model spectra with COBE data. These CMB maps are analyzed using the number of anisotropy hot spots and their boundary curvature. CMB maps which account for instrumental effects and sky coverage are Monte Carlo gener...
1993-11-28
2008-02-03
[ "astro-ph" ]
Sergio Torres
astro-ph/9311063
An Analysis of IRAS Identified Hii Regions and their Radio Properties
To try and confirm the types of object in the list of 2298 potential HII regions identified by Hughes \& MacLeod from the IRAS Point Source Catalog, we selected a sample of 82 for observing at the VLA. We selected half with values of Y = log(F$_{25}$/F$_{12}$) $\geq$ 0.8, and for control purposes, half with values of 0...
1993-11-26
2009-10-22
[ "astro-ph" ]
V.A.Hughes, and G.C.MacLeod
astro-ph/9311064
Oxygen Abundances in Low Surface Brightness Disk Galaxies
The oxygen abundances in the \HII regions of a sample of low surface brightness (LSB) disk galaxies are presented. In general, LSB galaxies are found to be metal poor ($Z < {1 \over 3} Z\solar$). Indeed, some LSB galaxies rival the lowest abundance extragalactic objects known. These low metallicities indicate that LSB ...
1993-11-25
2009-10-22
[ "astro-ph" ]
Stacy McGaugh
astro-ph/9311062
Gravitational Lenses and Unconventional Gravity Theories
We study gravitational lensing by clusters of galaxies in the context of the generic class of unconventional gravity theories of the scalar--tensor type. For positive energy scalar fields with any dynamics, the bending of light by a weakly gravitating system (galaxy or cluster) is always smaller than the bending predic...
1993-11-25
2010-11-01
[ "astro-ph", "gr-qc" ]
Jacob D. Bekenstein and Robert H. Sanders
astro-ph/9311065
Lyman Alpha Absorption and Tidal Debris
It is suggested that a significant fraction of the low column-density absorption features seen in the spectra of quasars are produced in pressure-confined tidal debris, that was built up in small groups and clusters of galaxies over a Hubble time. We show that the space-density and cross-section of tidal tails in group...
1993-11-25
2009-10-22
[ "astro-ph" ]
Simon L. Morris and Sidney van den Bergh
astro-ph/9311066
The Nonlinear Evolution of Rare Events
In this paper I consider the nonlinear evolution of a rare density fluctuation in a random density field with Gaussian fluctuations, and I rigorously show that it follows the spherical collapse dynamics applied to its mean initial profile. This result is valid for any cosmological model and is independent of the shape ...
1993-11-25
2009-10-22
[ "astro-ph" ]
F. Bernardeau
astro-ph/9311061
Resolving the Beta-Discrepancy for Clusters of Galaxies
Previous comparisons of optical and X-ray observations of clusters of galaxies have lead to the so-called ``$\beta$ - discrepancy'' that has persisted for the last decade. The standard hydrostatic-isothermal model for clusters predicts that the parameter $\beta_{spec} = \sigma_{r}^{2}/(kT/\mu m_{p})$, which describes t...
1993-11-24
2009-10-22
[ "astro-ph" ]
Neta A. Bahcall and Lori M. Lubin
astro-ph/9311056
Non-Linear Approximations to Gravitational Instability: A Comparison in Second-Order Perturbation Theory
Nonlinear approximation methods such as the Zeldovich approximation, and more recently the frozen flow and linear potential approximations, are sometimes used to simulate nonlinear gravitational instability in the expanding Universe. We investigate the relative accuracy of these approximations by comparing them with th...
1993-11-23
2009-10-22
[ "astro-ph" ]
D. Munshi and A. A. Starobinsky
astro-ph/9311057
Reconstructing the linear power spectrum of cosmological mass fluctuations
We describe an attempt to reconstruct the initial conditions for the formation of cosmological large-scale structure. The power spectrum of the primordial fluctuations is affected by bias, nonlinear evolution and redshift-space distortions, but we show how these effects can be corrected for analytically. Using eight in...
1993-11-23
2015-06-24
[ "astro-ph" ]
J.A. Peacock & S.J. Dodds
astro-ph/9311060
The Brightest Stars in Galaxies Are Not Good Distance Indicators -
Use of the brightest stars in galaxies as a distance indicator and claims that the method supports the `short' distance scale are examined. Data from several different observational programmes are brought together for the first time with a procedure for the careful accounting of errors. The true uncertainties of the me...
1993-11-23
2007-05-23
[ "astro-ph" ]
Richard Rozanski, Michael Rowan-Robinson (Queen Mary and Westfield College, London, UK)
astro-ph/9311058
Neutrino Pair Bremsstrahlung in Neutron Star Crusts: a Reappraisal
We demonstrate that band-structure effects suppress bremsstrahlung of neutrino pairs by electrons in the crusts of neutron stars at temperatures of the order of $5\times 10^9 \,{\rm K}$ and below. Taking this into account, together with the fact that recent work indicates that the masses of neutron star crusts are cons...
1993-11-23
2009-10-22
[ "astro-ph" ]
C. J. Pethick and Vesteinn Thorsson
astro-ph/9311059
Wiener Reconstruction of Galaxy Surveys in Spherical Harmonics
The analysis of whole-sky galaxy surveys commonly suffers from the problems of shot-noise and incomplete sky coverage (e.g. at the Zone of Avoidance). The orthogonal set of spherical harmonics is utilized here to expand the observed galaxy distribution. We show that in the framework of Bayesian statistics and Gaussian ...
1993-11-23
2009-10-22
[ "astro-ph" ]
O. Lahav, K.B. Fisher, Y. Hoffman, C. A. Scharf, and S. Zaroubi
astro-ph/9311055
The Quasi-Linear Evolution of the Density Field in Models of Gravitational Instability
Two quasi-linear approximations, the frozen flow approximation (FFA) and the frozen potential approximation (FPA), have been proposed recently for studying the evolution of a collisionless self-gravitating fluid. In the FFA it is assumed that the velocity field remains unchanged from its value obtained from the linear ...
1993-11-22
2015-06-24
[ "astro-ph", "hep-ph" ]
F. Bernardeau, T. P. Singh, B. Banerjee, S. M. Chitre
astro-ph/9311052
Testing the Gravitational Instability Hypothesis?
We challenge a widely accepted assumption of observational cosmology: that successful reconstruction of observed galaxy density fields from measured galaxy velocity fields (or vice versa), using the methods of gravitational instability theory, implies that the observed large-scale structures and large-scale flows were ...
1993-11-19
2009-10-22
[ "astro-ph" ]
A. Babul, D. Weinberg, A. Dekel & J. Ostriker
astro-ph/9311054
Cosmology/COBE
Abbreviated abstract of an invited talk at the International Cosmic Ray Conference in Calgary, July 1993: The results from the COBE satellite are in close agreement with the predictions of the standard hot Big Bang model, suggesting that the Universe was once hot, dense and isothermal, giving a background radiation spe...
1993-11-19
2007-05-23
[ "astro-ph" ]
Edward L. Wright
astro-ph/9311053
Power Spectrum Independent Constraints on Cosmological Models
A formalism is presented that allows cosmological experiments to be tested for consistency, and allows a simple frequentist interpretation of the resulting significance levels. As an example of an application, this formalism is used to place constraints on bulk flows of galaxies using the results of the microwave backg...
1993-11-19
2009-10-07
[ "astro-ph" ]
Max Tegmark, Emory Bunn and Wayne Hu
astro-ph/9311046
Gravitational microlensing: a method for detecting halo dark matter
It has been shown by Paczy\'nski that gravitational microlensing is potentially a useful method for detecting the dark constituents of the halo of our galaxy, if their mass lies in the approximate domain $10^{-6} < M/M_{\odot} < 10^{-1}$. Microlensing observations now under way monito several millions of stars in the L...
1993-11-18
2008-02-03
[ "astro-ph" ]
Philippe Jetzer
astro-ph/9311051
Microwave backgropund anisotropies, large-scale structure and cosmological parameters
We review how the various large-scale data constrain cosmological parameters and, consequently, theories for the origin of large-scale structure in the Universe. We discuss the form of the power spectrum implied by the correlation data of galaxies and argue by comparing the velocity field implied by the distribution of...
1993-11-18
2007-05-23
[ "astro-ph" ]
A. Kashlinsky
astro-ph/9311045
Gravitational microlensing by the dark halo of M31
It has been shown by Paczy\'nski that gravitational microlensing is potentially a useful method for detecting the dark constituents of the halo of our galaxy, if their mass lies in the approximate domain $10^{-6}<M/M_\odot<10^{-1}$. Microlensing observations now im progress monitor several millions of stars in the Larg...
1993-11-18
2008-02-03
[ "astro-ph" ]
Philippe Jetzer
astro-ph/9311050
Gamma-Ray Bursts are Time-Asymmetric
A simple test for time-asymmetry is devised and carried out on the brightest gamma-ray bursts detected by the Burst and Transient Source Experiment (BATSE) on board the {\it Compton} Gamma Ray Observatory. We show evidence that individual bursts are time-asymmetric on all time scales tested, from a time scale shorter t...
1993-11-18
2009-10-22
[ "astro-ph" ]
R. J. Nemiroff (USRA/GMU/NASA), J. P. Norris (NASA/GSFC), C. Kouveliotou (USRA/NASA), G. J. Fishman (NASA/MSFC), C. A. Meegan (NASA/MSFC), and W. S. Paciesas (UAH/NASA)
astro-ph/9311044
Is Dark Matter in Spiral Galaxies Cold Gas? II. Fractal Models and Star Non-Formation
Gas cloud models taking into account the recently disclosed fractal structure of cold gas are set up, showing that large errors in the classical gas mass determination based on smooth cloud models can easily follow if the gas is in reality fractal. Fractal clouds must present both optically thin and optically thick clu...
1993-11-18
2011-05-23
[ "astro-ph" ]
D. Pfenniger & F. Combes
astro-ph/9311047
Gravitational microlensing by the halo of the Andromeda galaxy
It has been shown by Paczy\'nski that gravitational microlensing is a useful method to detect brown dwarfs in the dark halo of our galaxy. At present several experiments are carried out to monitor several million stars in the Large Magellanic Cloud with the aim to find such microlensing events. Here I discuss the possi...
1993-11-18
2008-02-03
[ "astro-ph" ]
Philippe Jetzer
astro-ph/9311043
Is Dark Matter in Spiral Galaxies Cold Gas? I. Observational Constraints and Dynamical Clues About Galaxy Evolution
Based on dynamical constraints about the Hubble sequence evolution, observational data and a number of "conspiracies", we propose that the dark matter around spiral galaxies is in the form of cold gas, essentially in molecular form and rotationally supported. (full A&A paper (in press) available by anonymous ftp at obs...
1993-11-18
2011-05-23
[ "astro-ph" ]
D. Pfenniger, F. Combes & L. Martinet