Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 8 of 8
Full-Text Articles in Physics
Constraints On Vector Unparticle Physics From Cosmic Censorship, Jonas R. Mureika
Constraints On Vector Unparticle Physics From Cosmic Censorship, Jonas R. Mureika
Physics Faculty Works
Vector unparticle couplings to standard model fields produce repulsive corrections to gravity. From a general relativistic perspective, this leads to an effective Reissner-Nordstrom-like metric whose "charge" is a function of the unparticle coupling constant λ, and therefore can admit naked singularities. Requiring the system to respect cosmic censorship provides a new method of constraining the value of λ. These limits are extremely loose for stellar-mass black holes, but commensurate with existing bounds for primordial black holes. In the case of theoretical low-mass black holes, the bounds on λ are much stricter than those derived from astrophysical and accelerator …
The Initial Mass Function And Disk Frequency Of The Ρ Ophiuchi Cloud: An Extinction-Limited Sample, Kristen Erickson, Bruce Wilking, Michael Meyer, John Robinson, Lauren Stephenson
The Initial Mass Function And Disk Frequency Of The Ρ Ophiuchi Cloud: An Extinction-Limited Sample, Kristen Erickson, Bruce Wilking, Michael Meyer, John Robinson, Lauren Stephenson
Physics Faculty Works
We have completed an optical spectroscopic survey of an unbiased, extinction-limited sample of candidate young stars covering 1.3 deg2 of the ρ Ophiuchi star-forming region. While infrared, X-ray, and optical surveys of the cloud have identified many young stellar objects (YSOs), these surveys are biased toward particular stages of stellar evolution and are not optimal for studies of the disk frequency and initial mass function. We have obtained over 300 optical spectra to help identify 135 association members based on the presence of Hα in emission, lithium absorption, X-ray emission, a mid-infrared excess, a common proper motion, reflection nebulosity, and/or …
(1+1)-Dimensional Entropic Gravity, R. B. Mann, Jonas R. Mureika
(1+1)-Dimensional Entropic Gravity, R. B. Mann, Jonas R. Mureika
Physics Faculty Works
We consider the formulation of entropic gravity in two spacetime dimensions. The usual gravitational force law is derived even in the absence of area, as normally required by the holographic principle. A special feature of this perspective concerns the nature of temperature and entropy defined at a point. We argue that the constancy of the gravitational force in one spatial dimension implies the information contained at each point in space is an internal degree of freedom on the manifold, and furthermore is a universal constant, contrary to previous assertions that entropic gravity in one spatial dimension is ill-defined. We give …
Aspects Of Noncommutative (1+1)-Dimensional Black Holes, Jonas R. Mureika, Piero Nicolini
Aspects Of Noncommutative (1+1)-Dimensional Black Holes, Jonas R. Mureika, Piero Nicolini
Physics Faculty Works
We present a comprehensive analysis of the spacetime structure and thermodynamics of ( 1 + 1 )-dimensional black holes in a noncommutative framework. It is shown that a wider variety of solutions are possible than the commutative case considered previously in the literature. As expected, the introduction of a minimal length √ θ cures singularity pathologies that plague the standard two-dimensional general relativistic case, where the latter solution is recovered at large length scales. Depending on the choice of input parameters (black hole mass M, cosmological constant Λ , etc.), black hole solutions with zero, up to six, horizons …
Temporal And Spatial Aspects Of Gas Release During The 2010 Apparition Of Comet 103p/Hartley 2, M. Mumma, B. Bonev, G. Villanueva, L. Paganini, M. Disanti, E. Gibb, J. Keane, K. Meech, G. Blake, R. Ellis, M. Lippi, H. Boehnhardt, K. Magee-Sauer
Temporal And Spatial Aspects Of Gas Release During The 2010 Apparition Of Comet 103p/Hartley 2, M. Mumma, B. Bonev, G. Villanueva, L. Paganini, M. Disanti, E. Gibb, J. Keane, K. Meech, G. Blake, R. Ellis, M. Lippi, H. Boehnhardt, K. Magee-Sauer
Physics Faculty Works
We report measurements of eight primary volatiles (H2O, HCN, CH4, C2H6, CH3OH, C2H2, H2CO, and NH3) and two product species (OH and NH2) in comet 103P/Hartley 2 using high-dispersion infrared spectroscopy. We quantified the long- and short-term behavior of volatile release over a three-month interval that encompassed the comet's close approach to Earth, its perihelion passage, and flyby of the comet by the Deep Impact spacecraft during the EPOXI mission. We present production rates for individual species, their mixing ratios relative to water, and their spatial distributions in the coma on multiple dates. The production rates for water, ethane, HCN, …
Detecting Vanishing Dimensions Via Primordial Gravitational Wave Astronomy, Jonas R. Mureika, Dejan Stojkovic
Detecting Vanishing Dimensions Via Primordial Gravitational Wave Astronomy, Jonas R. Mureika, Dejan Stojkovic
Physics Faculty Works
Lower dimensionality at higher energies has manifold theoretical advantages as recently pointed out by Anchordoqui et al. [arXiv:1003.5914]. Moreover, it appears that experimental evidence may already exist for it: A statistically significant planar alignment of events with energies higher than TeV has been observed in some earlier cosmic ray experiments. We propose a robust and independent test for this new paradigm. Since ( 2 + 1 )-dimensional spacetimes have no gravitational degrees of freedom, gravity waves cannot be produced in that epoch. This places a universal maximum frequency at which primordial waves can propagate, marked by the transition between dimensions. …
Epoxi: Comet 103p/Hartley 2 Observations From A Worldwide Campaign ; Astrophysical Journal Letters, K. Meech, M. A'Hearn, J. Adams, P. Bacci, J. Bai, L. Barrera, M. Battelino, J. Bauer, E. Becklin, B. Bhatt, N. Biver, D. Bockelee-Morvan, D. Bodewits, H. Bohnhardt, J. Boissier, B. Bonev, W. Borghini, J. Brucato, E. Bryssinck, M. Buie, H. Canovas, D. Castellano, S. Charnley, W. Chen, P. Chiang, Y. Choi, D. Christian, Y. Chuang, Anita Cochran, P. Colom, M. Combi, I. Coulson, J. Crovisier, N. Russo, K. Dennerl, K. Dewahl, M. Disanti, M. Facchini, T. Farnham, Y. Fernandez, H. Floren, U. Frisk, T. Fujiyoshi, R. Furusho, T. Fuse, G. Galli, D. Garcia-Hernandez, A. Gersch, Z. Getu
Epoxi: Comet 103p/Hartley 2 Observations From A Worldwide Campaign ; Astrophysical Journal Letters, K. Meech, M. A'Hearn, J. Adams, P. Bacci, J. Bai, L. Barrera, M. Battelino, J. Bauer, E. Becklin, B. Bhatt, N. Biver, D. Bockelee-Morvan, D. Bodewits, H. Bohnhardt, J. Boissier, B. Bonev, W. Borghini, J. Brucato, E. Bryssinck, M. Buie, H. Canovas, D. Castellano, S. Charnley, W. Chen, P. Chiang, Y. Choi, D. Christian, Y. Chuang, Anita Cochran, P. Colom, M. Combi, I. Coulson, J. Crovisier, N. Russo, K. Dennerl, K. Dewahl, M. Disanti, M. Facchini, T. Farnham, Y. Fernandez, H. Floren, U. Frisk, T. Fujiyoshi, R. Furusho, T. Fuse, G. Galli, D. Garcia-Hernandez, A. Gersch, Z. Getu
Physics Faculty Works
Earth- and space-based observations provide synergistic information for space mission encounters by providing data over longer timescales, at different wavelengths and using techniques that are impossible with an in situ flyby. We report here such observations in support of the EPOXI spacecraft flyby of comet 103P/Hartley 2. The nucleus is small and dark, and exhibited a very rapidly changing rotation period. Prior to the onset of activity, the period was ~16.4 hr. Starting in 2010 August the period changed from 16.6 hr to near 19 hr in December. With respect to dust composition, most volatiles and carbon and nitrogen isotope …
Kinematical Conformal Cosmology: Fundamental Parameters From Astrophysical Observations, Gabriele U. Varieschi
Kinematical Conformal Cosmology: Fundamental Parameters From Astrophysical Observations, Gabriele U. Varieschi
Physics Faculty Works
No abstract provided.