118874471
Model-Independent Signatures of New Physics in non-Gaussianity
Instituut-Lorentz for Theoretical Physics, University of Leiden, Leiden 2333CA, The Netherlands(Dated: February 6, 2012)We compute the model-independent contributions to the primordial bispectrum and trispectrum inde Sitter space due to high-energy physics. We do this by coupling a light inaton to an auxiliaryheavy eld, and then evaluating correlation functions in the Schwinger-Keldysh \in-in" formalism.The high-energy physics produces corrections parametrized by H=Mwhere His the scale of ina-tion and M is the mass of the heavy eld. The bispectrum peaks near the elongated shape, butotherwise contains no features. On the other hand, the trispectrum contains oscillations which areof a magnitude possibly detectable using upcoming data. These oscillations are the cosmologicalanalogue of energy eigenstate mixing.
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.
13946666
A Quantum Mechanical Model of Spherical Supermembranes
We present a quantum mechanical model of spherical supermembranes. Using superfields to represent the cartesian coordinates of the membrane, we are able to exactly determine its supersymmetric vacua. We find there are two classical vacua, one corresponding to an extended membrane and one corresponding to a point-like membrane. For the = 2 case, instanton effects then lift these vacua to massive states. For the = 4 case, there is no instanton tunneling, and the vacua remain massless. Similarities to spherical supermembranes as giant gravitons and in Matrix theory on pp-waves is discussed.
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.
7559823
Interactions of cosmic superstrings
We develop methods by which cosmic superstring interactions can be studied in detail. These include the reconnection probability and emission of radiation such as gravitons or small string loops. Loop corrections to these are discussed, as well as relationships to (p; q)-strings. These tools should allow a phenomenological study of string models in anticipation of upcoming experiments sensitive to cosmic string radiation.
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.
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.
18221217
A REFINED EPHEMERIS AND PHASE-RESOLVED X-RAY SPECTROSCOPY OF THE GEMINGA PULSAR
We present a refined, phase-connected, postglitch ephemeris for the Geminga pulsar that is a good fit to all the postglitch data from EGRET, ASCA, and XMM-Newton. We also present the results of phase-resolved spectroscopy of two XMM-Newton X-ray observations of the Geminga pulsar obtained in 2002 and 2004. An investigation is made into a previously claimed existence of a small hot spot on the neutron star surface. We conclude that that interpretation was more likely an artifact of an overly restrictive assumption used to fit the phase-resolved spectra: namely, that the spectral index of the nonthermal component is constant. When we allow the spectral index to vary as a function of rotation phase, we find systematic variations in spectral index, and such fits do not require an additional hot blackbody component.
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 ...
23294225
A balloon-borne measurement of high latitude atmospheric neutrons using a licaf neutron detector
PoGOLino is a scintillator-based neutron detector. Its main purpose is to provide data on the neutron flux in the upper stratosphere at high latitudes at thermal and non-thermal energies for the PoGOLite instrument. PoGOLite is a balloon borne hard X-ray polarimeter for which the main source of background stems from high energy neutrons. No measurements of the neutron environment for the planned flight latitude and altitude exist. Furthermore this neutron environment changes with altitude, latitude and solar activity, three variables that will vary throughout the PoGOLite flight. PoGOLino was developed to study the neutron environment and the influences from these three variables upon it. PoGOLino consists of two Europium doped Lithium Calcium Aluminium Fluoride (Eu:LiCAF) scintillators, each of which is sandwiched between 2 Bismuth Germanium Oxide (BGO) scintillating crystals, which serve to veto signals produced by gamma-rays and charged particles. This allows the neutron flux to be measured even in high radiation environments. Measurements of neutrons in two separate energy bands are achieved by placing one LiCAF detector inside a moderating polyethylene shield while the second detector remains unshielded. The PoGOLino instrument was launched on March 20th 2013 from the Esrange Space Center in Northern Sweden to an altitude of 30.9 km. A description of the detector design and read-out system is presented. A detailed set of simulations of the atmospheric neutron environment performed using both PLANETOCOSMICS and Geant4 will also be described. The comparison of the neutron flux measured during flight to predictions based on these simulations will be presented and the consequences for the PoGOLite background will be discussed.