A Bit Far-Fetched But Interesting

The key point is that spacecraft can accurately know the distance to Earth with radio ranging but they don't know their position well perpendicular to the Earth-spacecraft line, so by using x-ray pulsars they could do better.   Some other possibly more realistic ideas:  how about using brighter radio pulsars or other spacecraft.   Spacecraft often use other spacecraft to relay data back to Earth, the timing of the response should be sufficient to determine range if the other systematics could be ironed out.

arXiv:1011.5095 [pdf, ps, other]
Title: Timing X-ray Pulsars with Application to Spacecraft Navigation
Authors: Mike Georg Bernhardt, Tobias Prinz, Werner Becker, Ulrich Walter

Kozai and Compact Objects

This paper dovetails nicely with Yanquin Wu's talk here last week.  Quite a fun idea.

arXiv:1011.4322 [pdf, ps, other]

Title: Accelerating Compact Object Mergers in Triple Systems with the Kozai Resonance: A Mechanism for "Prompt'' Type Ia Supernovae, Gamma-Ray Bursts, and Other Exotica

Authors: Todd A. Thompson

What if you could watch the universe change?

The authors propose an experiment where you actually measure the redshifts of objects changing with time (almost achievable now) and how the CMD changes with time (more fantastical).

 arXiv:1011.2646 [pdf, ps, other] Real-time Cosmology

Claudia Quercellini, Luca Amendola, Amedeo Balbi, Paolo Cabella, Miguel Quartin

Three Generations

The actual argument for three generations is a bit weak; however, this paper is definitely an interesting read with a quick history of the need for three generations to explain the experiments in the sixties and to account for baryogenesis.   As for why not more than three, is it just too unlikely.

 arXiv:1011.2761 (cross-list from hep-ph) [pdf, ps, other]

Anthropic Argument for Three Generations

Andrew Gould

Is the universe isotropic?

I reckoned that it is a good idea to check this out.  Ralston outlines how to quantify the anisotropy of various observations and of course finds it.   The quantification and potential observations are useful, the finding it is a lot harder to believe.

arXiv:1011.2240 [pdf, ps, other] Question Isotropy John P. Ralston

The Chameleon and the Giant

A Chameleon scalar field in scalar-tensor gravity is a field that modifies the strength of gravity at low densities and large length scales.  It disappears below a thin layer of high density material, so it would affect the structure of most stars.   However, the outer layers of giant stars especially supergiants like Betelgeuse are essentially hot vacuums, so the chameleon would not be fully shielded here and would change the structure of these stars.

arXiv:1011.4107 [pdf, ps, other]

Stellar Structure and Tests of Modified Gravity

Philip Chang, Lam Hui

Neutron-Star Optics

Researchers have generally assumed that the spacetime surrounding a neutron star is well approximated by Schwarschild or Kerr to calculate ray tracing because of the high degree of symmetry of these spacetimes.  Psaltis and Jonahannsen present a new algorithm that goes beyond these toy models and use a metric with an arbitrary quadrupole moment.  This requires integrating 2nd-order ODES (rather than the 1st-order in the case of Kerr).  They outline some systems where this technique provides potentially important diagnostics.

 arXiv:1011.4078 [pdf, ps, other]

A Ray-Tracing Algorithm for Spinning Compact Object Spacetimes with Arbitrary Quadrupole Moments. I. Quasi-Kerr Black Holes

Dimitrios Psaltis, Tim Johannsen (Arizona)