Friday, December 26, 2008

Is Dark Matter Neutrinos?

Do non-relativistic neutrinos constitute the dark matter?
The observed dark matter distribution of a supercluster of galaxies is modelled by non-relativistic neutrinos. There is other evidence against this, however, some of which is mentioned in the paper.

Saturn Orbit Anomaly

On the recently determined anomalous perihelion precession of Saturn
The astronomer E.V. Pitjeva, by analyzing with the EPM2008 ephemerides a large number of planetary observations including also two years (2004-2006) of normal points from the Cassini spacecraft, phenomenologically estimated a statistically significant non-zero correction to the usual Newtonian/Einsteinian secular precession of the longitude of the perihelion of Saturn, i.e. \Delta\dot\varpi_Sat = -0.006 +/- 0.002 arcsec/cy; the formal, statistical error is 0.0007 arcsec/cy. It can be explained neither by any of the standard classical and general relativistic dynamical effects mismodelled/unmodelled in the force models of the EPM2008 ephemerides nor by several exotic modifications of gravity recently put forth to accommodate certain cosmological/astrophysical observations without resorting to dark energy/dark matter. Both independent analyses by other teams of astronomers and further processing of larger data sets from Cassini will be helpful in clarifying the nature and the true existence of the anomalous precession of the perihelion of Saturn.

Monday, December 22, 2008

Volcanic Eruption in HD

Guatemala's Mt. Santiaguito

More than one Time Dimension

Multiple Time Dimensions
The possibility of physics in multiple time dimensions is investigated. Drawing on recent work by Walter Craig and myself, I show that, contrary to conventional wisdom, there is a well-posed initial value problem--deterministic, stable evolution--for theories in multiple time dimensions. Though similar in many ways to ordinary, single-time theories, multi-time theories have some rather intriguing properties which suggest new directions for the understanding of fundamental physics.

Cosmic Microwave Background (CMB) Asymmetry

Title: Power Asymmetry in Cosmic Microwave Background Fluctuations from Full Sky to Sub-degree Scales: Is the Universe Isotropic?
Our results indicate that the reported common asymmetric axis extending over a large range in scales is highly unlikely to be a statistical fluke. Foregrounds and systematic effects do not seem to be probable explanations. The CMB does seem to have an uneven power distribution on the sky over a large range of angular scales. An important task for further research is to find a physical explanation for this asymmetry which can predict possible effects on CMB polarization to be tested in future experiments.

Sunday, December 21, 2008

Graphene Sheets

Graphene Recipe Yields Carbon Cornucopia in Science.
The hottest material in physics these days is graphene, sheets of carbon just a single atom thick. Graphene is flexible yet harder than diamond. It conducts electricity faster at room temperature than anything else. And it's nearly transparent, a handy property for devices such as solar cells and displays that need to let light through. The only trouble is that people have been able to make only small flakes of the stuff--until now.

Friday, December 19, 2008

"Axis of Evil"

Does the Universe Have a Handedness?
In this article I extend an earlier study of spiral galaxies in the Sloan Digital Sky Survey (SDSS) to investigate whether the universe has an overall handedness. A preference for spiral galaxies in one sector of the sky to be left-handed or right-handed spirals would indicate a parity-violating asymmetry in the overall universe and a preferred axis. The previous study used 2616 spiral galaxies with redshifts <0.04 and identified handedness. The new study uses 15872 with redshifts <0.085 and obtains very similar results to the first with a signal exceeding 5 sigma, corresponding to a probability of 2.5x10-7 for occurring by chance. The axis of the dipole asymmetry lies at approx. (l, b) =(32d,69d), roughly along that of our Galaxy and close to the so-called "Axis of Evil".

Tuesday, December 16, 2008

Strategic Pizza

How to eat 4/9 of a pizza
Given two players alternately picking pieces of a pizza sliced by radial cuts, in such a way that after the first piece is taken every subsequent chosen piece is adjacent to some previously taken piece, we provide a strategy for the starting player to get 4/9 of the pizza. This is best possible and settles a conjecture of Peter Winkler.

Red Rectangle Nebula

Red Rectangle Nebula

Monday, December 15, 2008

Human DNA weirdness

In PNAS: The human genome in the LINE of fire.
One of the most surprising revelations of the sequencing of the human genome was that nearly half of our DNA is derived from transposable element (TE) insertions, and this is likely to be an underestimate, because many TE-derived sequences have diverged beyond recognition (1). Remarkably, the vast majority of human TE sequences result from the activity of a single class of TEs known as LINE retrotransposons. Represented by the currently active LINE-1 or L1 elements, LINEs are autonomous TEs that propagate in the genome by making RNA copies of themselves that are subsequently reverse transcribed and integrated into the genome (2–4). As a result of their ongoing activity during the past 150 million years, L1 elements account for approximately one-third of the human genome ...

Eukaryotes are a kind of Archea?

Are there three great domains of life - the Archea, Eubacteria and Eukaryotes? Or are the Eukaryotes most closely related to the Eocytes, a particular group with the Archea. This paper in PNAS supports the latter: The archaebacterial origin of eukaryotes.

Friday, December 12, 2008

Missing Baryons

Evidence for the Missing Baryons in the Angular Correlation of the Diffuse X-ray Background
The amount of detected baryons in the local Universe is at least a factor of two smaller than measured at high redshift. It is believed that a significant fraction of the baryons in the current Universe is "hiding" in a hot filamentary structure filling the intergalactic space, the Warm-Hot Intergalactic Medium ($WHIM$). We found evidence of the missing baryons in the $WHIM$ by detecting their signature on the angular correlation of diffuse X-ray emission with the XMM-Newton satellite

Wednesday, December 10, 2008

The Center of the Milky Way

The warped young stellar disc in the Galactic Centre
Within the central parsec of the Galaxy, several tens of young stars orbiting a central supermassive black hole are observed. A subset of these stars forms a coherently rotating disc. Other observations reveal a massive molecular torus which lies at a radius ~1.5pc from the centre. In this paper we consider the gravitational influence of the molecular torus upon the stars of the stellar disc. We derive an analytical formula for the rate of precession of individual stellar orbits and we show that it is highly sensitive upon the orbital semi-major axis and inclination with respect to the plane of the torus as well as on the mass of the torus. Assuming that both the stellar disc and the molecular torus are stable on the time-scale >6Myr, we constrain the mass of the torus and its inclination with respect to the young stellar disc. We further suggest that all young stars observed in the Galactic Centre may have a common origin in a single coherently rotating structure with an opening angle <5deg, which was partially destroyed (warped) during its lifetime by the gravitational influence of the molecular torus.

Saturday, December 06, 2008

Blood Simple

I just watched Blood Simple a clever, macabre, suspenseful DVD by the Coen Brothers.

Wednesday, December 03, 2008

Werner Herzog

I'm currently watching Even Dwarfs Started Small a rather eccentric film directed by Werner Herzog. I've also seen two other films by him recently: Grizzly Man and My Best Fiend both documentaries, both fascinating. Aguirre, the Wrath of God is another interesting and unusual film by the same director starting Klaus Kinski, who was also the subject of My Best Fiend.
poster for Aguirre