Thursday, July 31, 2008

NASA Confirms Water on Mars

NASA scientists said on Thursday they had definitive proof that water exists on Mars after tests on ice found on the planet in June by the Phoenix Mars Lander.

Until now, the evidence for ice has been circumstantial. That was based on photos Phoenix took of a hard splotchy area near its landing site and changes it saw in a trench.

The robot heated up ice in one of its instruments earlier this week. Scientists say the chemical test confirms the presence of ice near the Martian north pole.



Monday, July 28, 2008

Tree Quantum Field Theory

Gurau et. al. posted a new paper today on arxiv ( [hep-th]), proposing a new approach to quantum field theory: marked trees.
We propose a new formalism for quantum field theory which is neither based on functional integrals, nor on Feynman graphs, but on marked trees. This formalism is constructive, i.e. it computes correlation functions through convergent rather than divergent expansions. It applies both to Fermionic and Bosonic theories. It is compatible with the renormalization group, and it allows to define non-perturbatively {\it differential} renormalization group equations. It accommodates any general stable polynomial Lagrangian. It can equally well treat noncommutative models or matrix models such as the Grosse-Wulkenhaar model. Perhaps most importantly it removes the space-time background from its central place in QFT, paving the way for a nonperturbative definition of field theory in noninteger dimension.

SU(5) Grand Unified Model from Non-perturbative String Theory

Mirjam Cvetic and Timo Weigand posted a new paper today (arXiv:0807.3953v2 [hep-th]) on symmetry breaking and SU(5) GUT model building from supergravity/non-perturbative string theory. The abstract is as follows:

We propose a robust supergravity model of dynamical supersymmetry breaking and gauge mediation, and a natural embedding in non-perturbative string theory with D-branes. A chiral field (and its mirror) charged under "anomalous" U(1)'s acts as a Polonyi field whose hierarchical Polonyi-term can be generated by string instantons. Further quartic superpotential terms arise naturally as a tree-level decoupling effect of massive string states. A robust supersymmetry breaking minimum allows for gauge mediation with soft masses at the TeV scale, which we realise for a globally consistent SU(5) GUT model of Type I string theory, with a D1-instanton inducing the Polonyi term.

Former Google Engineers Launch Cuil Search Engine

A former Google employee and her husband launched a new search engine Monday called Cuil (pronounced "cool",, aiming to topple Google by indexing more Web pages than the search giant.

Cuil, of Menlo Park, California, is led by Anna Patterson , a former leader of Google's search index and her husband, Tom Costello, who researched and developed search engines at Stanford University and IBM. The two, president and CEO, respectively, met at Stanford.

Russell Power, the third cofounder of the group, also worked at Google on search indexing, Web rankings, and spam detection. He works as vice president of engineering at Cuil.

The company, which shaved an 'L' off its name to become Cuil, said it has indexed 120 billion Web pages and can provide results organized by ideas with complete privacy for users.

Google on Friday said it had discovered 1 trillion unique Web pages on the Internet, but did not give an updated number on how many of those pages it has indexed.

Cuil said its search engine goes beyond traditional approaches by analyzing the context of each page and the concepts behind each query so it can provide better rankings by content rather than popularity. Cuil then organizes similar results into groups and sorts them by category. It also offers tabs to clarify subjects, as well as suggestions on how to refine searches.

Cuil isn't the first Google rival to launch this year. Wikia Search, a highly anticipated search engine from Wikipedia founder Jimmy Wales, made its official debut in January . Wikia Search hopes to provide better search results by allowing a community of users to index pages by using their Web page rankings and other suggestions, as well as its own indexing of the Web.


Saturday, July 26, 2008

The Dark Knight's Suit

In "The Dark Knight," Batman complains that he needs a better suit - and that's a concern for the real-life knights in the U.S. military as well. The Pentagon would love to have Wayne Enterprises' secret for lighter, more flexible body armor. Nanocomp Technologies based in New Hampshire, is among several companies working on carbon-nanotube composites for military applications.

"We're really focused on trying to create layers of protection that would improve things for our troops," Peter Antoinette, Nanocomp's president and chief executive officer, told me. "It would take a number of years before you could order up a suit, and then a billionaire would have to pay seven figures for a suit that would work the way they do in the movies."

As an initial step, Nanocomp is working on nanotubes for next-generation wiring in satellites and aircraft. Carbon nanotubes are highly conductive and could replace copper wire in settings where reducing weight is crucial. "We're less than one-tenth the weight of copper, so if you can take 1,000 pounds off these satellites or aircraft, you'd be saving a huge amount of money," Antoinette said.

Commercialization of nanotube wiring could begin as early as next year, Antoinette said. He added that Nanocomp's materials are already undergoing military testing, and body-armor applications could start emerging in 2010 or so.

Kakalios agreed that nanotubes are a technology to watch: "Compared to steel cables, it's about 100 times stronger. Whether you can make this in large enough quantities, in long enough length scales ... that work is still in progress."


Northern Lights Explained

NASA released findings Thursday that indicate magnetic explosions about one-third of the way to the moon cause the northern lights, or aurora borealis, to dance across the sky in spectacular shapes and colors.

A fleet of five small satellites, called Themis, observed the beginning of a geomagnetic storm in February, while ground observatories recorded the brightening of the northern lights.

A team led by UCLA scientist Vassilis Angelopoulos confirmed that the observed storm about 80,000 miles from Earth was triggered by a phenomenon known as magnetic reconnection. Every so often, the Earth's magnetic field lines are stretched like rubber bands by solar energy, snap, are thrown back to Earth and reconnect, in effect creating a short circuit.

This stored-up energy powers the northern and southern lights, Angelopoulos said.

LA Times

Friday, July 04, 2008

Xian-Jin Li and an attempted Proof of the Riemann Hypothesis

A new paper by Xian-Jin Li was uploaded on arxiv this week, with a claimed "proof" of the Riemann Hypothesis. Well, a "proof" is actually given for E. Bombieri's refinement of A. Weil's positivity condition, which implies the Riemann Hypothesis. The "proof" is said to be in the spirit of Alain Connes' approach to the Riemann Hypothesis.

Fortunately, (or unfortunately) it didn't take too long for Fields medalists to punch holes in the purported proof. Alain Connes himself, as well as Terence Tao pointed out certain problems on pages 20 and 29.

Alain Connes politely states in his blog:

I dont like to be too negative in my comments. Li's paper is an attempt to prove a variant of the global trace formula of my paper in Selecta. The "proof" is that of Theorem 7.3 page 29 in Li's paper, but I stopped reading it when I saw that he is extending the test function h from ideles to adeles by 0 outside ideles and then using Fourier transform (see page 31). This cannot work and ideles form a set of measure 0 inside adeles (unlike what happens when one only deals with finitely many places).

While Terence Tao, adds:

It unfortunately seems that the decomposition claimed in equation (6.9) on page 20 of that paper is, in fact, impossible; it would endow the function h (which is holding the arithmetical information about the primes) with an extremely strong dilation symmetry which it does not actually obey. It seems that the author was relying on this symmetry to make the adelic Fourier transform far more powerful than it really ought to be for this problem.

Xian-Jin Li has since posted revisions of his paper, specifically making changes on page 20 and 29, where Connes and Tao pointed out difficulties. However, it is doubtful Connes and Tao will take another look at the new version of the paper.