16544780
XMM-Newton, Chandra, and CGPS observations of the Supernova Remnants G85.4+0.7 and G85.9–0.6
We present an XMM-Newton detection of two low radio surface brightness supernova remnants (SNRs), G85.4+0.7 and G85.9–0.6, discovered with the Canadian Galactic Plane Survey (CGPS). High-resolution XMM-Newton images revealing the morphology of the diffuse emission, as well as discrete point sources, are presented and correlated with radio and Chandra images. The new data also permit a spectroscopic analysis of the diffuse emission regions, and a spectroscopic and timing analysis of the point sources. Distances have been determined from H I and CO data to be 3.5 ± 1.0 kpc for SNR G85.4+0.7 and 4.8 ± 1.6 kpc for SNR G85.9–0.6. The SNR G85.4+0.7 is found to have a temperature of ~12-13 MK and a 0.5-2.5 keV luminosity of ~(1–4) × 1033D23.5 erg s−1 (where D3.5 is the distance in units of 3.5 kpc), with an electron density ne of ~(0.07–0.16) (fD3.5)−1/2 cm−3 (where f is the volume filling factor) and a shock age of ~(9–49) (fD3.5)1/2 kyr. The SNR G85.9–0.6 is found to have a temperature of ~15-19 MK and a 0.5-2.5 keV luminosity of ~(1–4) × 1034D24.8 erg s−1 (where D4.8 is the distance in units of 4.8 kpc), with an electron density ne of ~(0.04–0.10) (fD4.8)−1/2 cm−3 and a shock age of ~(12–42) (fD4.8)1/2 kyr. Based on the data presented here, none of the point sources appears to be the neutron star associated with either SNR.
119245531
Observational evidence of dissipative photospheres in gamma-ray bursts
The emission from a gamma-ray burst (GRB) photosphere can give rise to a variety of spectral shapes. The spectrum can retain the shape of a Planck function or it can be broadened and have the shape ...
14372942
A NEW SPIN ON QUANTUM GRAVITY
We suggest that the (small but nonvanishing) cosmological constant, and the holographic properties of gravitational entropy, may both reflect unconventional quantum spin statistics at a fundamental level. This conjecture is motivated by the nonlocality of quantum gravity and the fact that spin is an inherent property of space–time. As an illustration we consider the "quon" model, which interpolates between Fermi and Bose statistics, and show that this can naturally lead to an arbitrarily small cosmological constant. In addition to laboratory tests, we briefly discuss the possible observable imprint on cosmological fluctuations from inflation.
3247660
Spin-statistics violations in superstring theory
I describe how superstring theory may violate spin statistics in an experimentally observable manner. Reviewing the basics of superstring interactions and how to utilize these to produce a statistical phase, I then apply these ideas to two specific examples. The first is the case of heterotic world sheet linkings, whereby one small closed string momentarily enlarges sufficiently to pass over another, producing such a statistical phase. The second is the braneworld model with noncommutative geometry, whereby matter composed of open strings may couple to a background in which spacetime coordinates do not commute, modifying the field (anti)commutator algebra. I conclude with ways to sharpen and experimentally test these exciting avenues to possibly verify superstring theory.
276424
Gravitational Wave Bursts from Cosmic Superstring Reconnections
We compute the gravitational waveform produced by cosmic superstring reconnections. This is done by first constructing the superstring reconnection trajectory, which closely resembles that of classical, instantaneous reconnection but with the singularities smoothed out due to the string path integral. We then evaluate the graviton vertex operator in this background to obtain the burst amplitude. The result is compared to the detection threshold for current and future gravitational wave detectors, finding that neither bursts nor the stochastic background would be detectable by Advanced LIGO. This disappointing but anticipated conclusion holds even for the most optimistic values of the reconnection probability and loop sizes.
15602764
Two black hole holography, lensing, and intensity
We numerically verify the analysis of the 'expanding horizon' theory of Susskind in relation to the 't Hooft holographic conjecture. By using a numerical simulation to work out the holographic image formed by two black holes upon a screen very far away, it is seen that it is impossible for a horizon to hide behind another. We also compute the holographic intensity distribution of such an arrangement.