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Articles 1 - 9 of 9
Full-Text Articles in Physical Sciences and Mathematics
Non-Vacuum Ads Cosmologies And The Approach To Equilibrium Of Entanglement Entropy, Sebastian Fischetti, David Kastor, Jennie Traschen
Non-Vacuum Ads Cosmologies And The Approach To Equilibrium Of Entanglement Entropy, Sebastian Fischetti, David Kastor, Jennie Traschen
David Kastor
We extend standard results for vacuum asymptotically locally AdS (AlAdS) spacetimes, showing that such spacetimes can be constructed as foliations where the induced metric on each hypersurface satisfies Einstein's equation with stress-energy. By an appropriate choice of stress-energy on the hypersurfaces, the resulting AlAdS spacetime satisfies Einstein's equation with a negative cosmological constant and physical stress tensor. We use this construction to obtain AlAdS solutions whose boundaries are FRW cosmologies sourced by a massless scalar field or by a perfect fluid obeying the strong energy condition. We focus on FRW universes that approach Minkowski spacetime at late times, yielding AlAdS …
Cosmic Sound In The Lyman Alpha Forest, Spencer Everett, Matt Kwiecien, Cordell Newmiller
Cosmic Sound In The Lyman Alpha Forest, Spencer Everett, Matt Kwiecien, Cordell Newmiller
DePaul Discoveries
Using the Baryon Oscillation Spectroscopic Survey (BOSS) from the Sloan Digital Sky Survey (SDSS), the authors attempt to detect the baryonic acoustic oscillations (BAOs) using the discrete wavelet transform. The wavelet transform is used to construct the power spectrum of intergalactic clouds of matter at large (Mpc) distance scales. It was found that the wavelet transform used here does not have high enough resolution to detect the BAOs. However, the techniques used in this study allow for future improvements in the transform that could potentially resolve the expected peak in the power spectrum and indicate the existence of BAOs.
String Fluid Cosmological Model With Magnetic Field In Bimetric Theory Of Gravitation, M. S. Borkar, N. P. Gaikwad
String Fluid Cosmological Model With Magnetic Field In Bimetric Theory Of Gravitation, M. S. Borkar, N. P. Gaikwad
Applications and Applied Mathematics: An International Journal (AAM)
In this paper, LRS Bianchi type I string fluid cosmological model with magnetic field in bimetric theory of gravitation is investigated by assuming barotropic equation of state for pressure and density and assuming the bulk viscosity to be inversely proportional to the scalar expansion. The source of energy momentum tensor is a bulk viscous fluid containing one dimensional string with electromagnetic field. The physical and geometrical properties of the model are discussed. The bulk viscosity affected the whole properties of the model.
Gemini Long-Slit Observations Of Luminous Obscured Quasars: Further Evidence For An Upper Limit On The Size Of The Narrow-Line Region, Kevin N. Hainline, Ryan C. Hickox, Jenny E. Greene, Adam D. Myers
Gemini Long-Slit Observations Of Luminous Obscured Quasars: Further Evidence For An Upper Limit On The Size Of The Narrow-Line Region, Kevin N. Hainline, Ryan C. Hickox, Jenny E. Greene, Adam D. Myers
Dartmouth Scholarship
We examine the spatial extent of the narrow-line regions (NLRs) of a sample of 30 luminous obscured quasars at 0.4 < z < 0.7 observed with spatially resolved Gemini-N GMOS long-slit spectroscopy. Using the [O III] λ5007 emission feature, we estimate the size of the NLR using a cosmology-independent measurement: the radius where the surface brightness falls to 10–15 erg s–1 cm–2 arcsec–2. We then explore the effects of atmospheric seeing on NLR size measurements and conclude that direct measurements of the NLR size from observed profiles are too large by 0.1-0.2 dex on average, as compared to measurements made to best-fit Sérsic or Voigt profiles convolved with the seeing. These data, which span a full order of magnitude in IR luminosity (log (L 8 μm/erg s–1) = 44.4-45.4), …
Supernovae Wavelet Spectral Index Method: A Step Toward Precision Cosmology, Andrew J. Wagers, Lifan Wang, Steve Asztalos
Supernovae Wavelet Spectral Index Method: A Step Toward Precision Cosmology, Andrew J. Wagers, Lifan Wang, Steve Asztalos
The Research and Scholarship Symposium (2013-2019)
As cosmological probes, Type Ia Supernovae are some of the most useful. These exploding stars are used to measure cosmic distances and are useful to test and refine cosmological models. While SNe Ia are extremely uniform, the need for more precise measurements of the peak magnitude has led to the development of methods to correct current measurements for statistical errors. The work presented here has developed a new method for measuring the strength of spectral lines with a goal of using them as a basis for correcting the measured peak magnitudes. Wavelets were used to decompose the spectra so that …
Lensed Type Ia Supernovae As Probes Of Cluster Mass Models, J Nordin, David Rubin, J Richard, E Rykoff, Greg Aldering, R Amanullah, H Atek, K Barbary, S Deustua, H K. Fakhouri, A S. Fruchter, A Goobar, I Hook, E Y. Hsiao, Xiaosheng Huang, J P. Kneib, C Lidman, J Meyers, S Perlmutter, C Saunders, A L. Spadafora, N Suzuki
Lensed Type Ia Supernovae As Probes Of Cluster Mass Models, J Nordin, David Rubin, J Richard, E Rykoff, Greg Aldering, R Amanullah, H Atek, K Barbary, S Deustua, H K. Fakhouri, A S. Fruchter, A Goobar, I Hook, E Y. Hsiao, Xiaosheng Huang, J P. Kneib, C Lidman, J Meyers, S Perlmutter, C Saunders, A L. Spadafora, N Suzuki
Physics and Astronomy
Using three magnified Type Ia supernovae (SNe Ia) detected behind CLASH (Cluster Lensing and Supernovae with Hubble) clusters, we perform a first pilot study to see whether standardizable candles can be used to calibrate cluster mass maps created from strong lensing observations. Such calibrations will be crucial when next-generation Hubble Space Telescope cluster surveys (e.g. Frontier) provide magnification maps that will, in turn, form the basis for the exploration of the high-redshift Universe. We classify SNe using combined photometric and spectroscopic observations, finding two of the three to be clearly of Type Ia and the third probable. The SNe exhibit …
It's About Time: Dynamics Of Inflationary Cosmology As The Source Of The Asymmetry Of Time, Emre Keskin
It's About Time: Dynamics Of Inflationary Cosmology As The Source Of The Asymmetry Of Time, Emre Keskin
USF Tampa Graduate Theses and Dissertations
This project is about the asymmetry of time. The main source of discontent for physicists and philosophers alike is that even though in every physical theory we developed and/or discovered for explaining how the universe functions, the laws are time reversal invariant; there seems to be a very genuine asymmetry between the past and the future. The aim of this project is to examine several attempts to solve this friction between the laws of physics and the asymmetry and provide a new proposal that makes use of modern cosmology. In the recent history of physics and in contemporary philosophy of …
Constraints On Cosmic Strings From The Ligo-Virgo Gravitational-Wave Detectors, J. Aasi, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.
Constraints On Cosmic Strings From The Ligo-Virgo Gravitational-Wave Detectors, J. Aasi, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.
Physics Faculty Research & Creative Works
Cosmic strings can give rise to a large variety of interesting astrophysical phenomena. Among them, powerful bursts of gravitational waves (GWs) produced by cusps are a promising observational signature. In this Letter we present a search for GWs from cosmic string cusps in data collected by the LIGO and Virgo gravitational wave detectors between 2005 and 2010, with over 625 days of live time. We find no evidence of GW signals from cosmic strings. From this result, we derive new constraints on cosmic string parameters, which complement and improve existing limits from previous searches for a stochastic background of GWs …
Cosmological And Astrophysical Tests Of Modified Gravity, Caixia Gao
Cosmological And Astrophysical Tests Of Modified Gravity, Caixia Gao
Electronic Theses and Dissertations
Three alternative theories to general relativity will be studied. The aim is to test these theories by applying them to astronomical objects or the cosmological background. The first one is unimodular relativity. The cosmological perturbation theory of this model is studied and the predictions on temperature fluctuations of the cmb are found. The second one is drgt massive gravity. In this theory a charged black hole solution is found and compared to those in gr, folloby constraints on the parameter space. The third one is a general massive gravity theory which shares the same background equation with the massless case …