Beyond Big Bang

Abhay Ashtekar (photo courtsey: Pennsylvania State Univ)

The universe started with a bang about 15 billion years back and went on expanding since then. Classical theories like Einstein's general theory of relativity can hope to explain the beginning upto a time very close to the actual 'bang' at which not only matter but space-time itself was born. The process of this understanding has been underway for many years now with the aid of careful observation of light and other kinds of electromagnetic radiation coming from deep sky and by devising clever theories to explain those observations.

But classical theories offer no clues about existence before that moment. Recently a research team at Penn State led by Prof. Abhay Ashtekar (Holder of the Eberly Family Chair in Physics and Director of the Institute for Gravitational Physics and Geometry at Penn State) has used quantum gravitational calculations to find threads that lead to an earlier time. The team showed that, prior to the Big Bang, there was a contracting universe with space-time geometry that otherwise is similar to that of our current expanding universe. Using quantum modifications of Einstein's cosmological equations, they have shown that as gravitational forces pulled this previous universe inward, it reached a point at which the quantum properties of space-time caused gravity to become repulsive, rather than attractive and instead of a sudden classical 'big bang', a 'quantum bounce' took place.

The idea of another universe existing prior to the Big Bang might have come naturally to many physicists or even non-physicists before this research, but this is the first systematic mathematical description that establishes its existence and also deduces properties of space-time geometry in that universe.

The research team used loop quantum gravity, a leading approach to the problem of the unification of general relativity with quantum physics -- an idea developed by Ashtekar in late 80s. The theory treats the space-time geometry itself as a discrete 'atomic' structure which in macroscopic scale looks like a continuum. This basic concept is not really unfamiliar to us -- We must remember that even our body and all solid things are actually made of 'void' at an atomic scale because most part of an atom is just empty space between orbiting electrons and a tiny nucleus (a nucleus is about 10000th times smaller than a typical atom in which it resides).

According to Ashtekar (but pardon our simplification), the fabric of space is literally woven by one-dimensional quantum threads. Near the Big-Bang, this fabric gets distorted by strong effects of gravitation and the quantum nature of geometry becomes important. It makes gravity strongly repulsive and gives rise to the Big 'Quantum' Bounce.

This research is reported in the current issue of Physical Review Letters. The paper is authored by Ashtekar and two of his post-doctoral researchers, Tomasz Pawlowski and Parmpreet Singh.

Superconductivity Theory Proven

Chandra Varma (Photo courtsey: UC-Riverside)

A French-German team of experimental scientists has announced that they could verify the central prediction of a high-temperature superconductivity theory proposed by a Prof Chandra Varma, currently a physics professor at the University of California-Riverside.

Superconductors are materials that conduct electricity with near-zero resistance below a specific temperature, known as the critical temperature. Superconductors typically find use in electric power transformers and magnetic resonance imaging machines. Conventional metallic superconductors must be cooled below -424 F to become superconducting.

The scientists say this verification might assist in the fabrication of materials that are superconducting at room temperature. And it will help settle a contentious, international debate on the fundamental physics of superconductivity and emergent states of matter.

Varma's initial theory, proposed in 1989 while he was working for IBM, stated the radical idea that high-temperature superconductivity and related phenomena occur in certain materials because quantum-mechanical fluctuations in those materials increase as temperature decreases. Usually such fluctuations -- determining the properties of all matter in the universe -- decrease as temperature decreases.

In 1996 Prof. Varma noted that in copper oxide materials superconductivity is associated with the formation of a new state of matter in which electric current loops form spontaneously, going from copper to oxygen atoms and back to copper. The French-Italian group directly observed the current loops in experiments involving the diffraction of polarized neutrons. In these experiments a beam of neutrons changes direction as well as the direction of its magnetization in a manner that is closely related to the geometrical arrangement of the current loops inside the material in which the beam is made to pass.

Results of this experimental verification is detailed in the May 19 issue of Physical Review Letters. Here's the abstract.

Hydrogen in Far Galaxy

A team of astronomers from European Southern Observatory (ESO) detected the presence of molecular hydrogen in the farthest system ever, an otherwise invisible galaxy that we observe when the Universe was less than 1.5 billion years old (The universe is estimated to be about 15 billion years old). The astronomers find that there is about one hydrogen molecule for 250 hydrogen atoms. This also implies that the gas in this galaxy must be rather cold, about -90 to -180 degrees Celsius. In addition, several lines from 'metals' are also seen, allowing the researchers to deduce the amount of various chemical elements.

The team arrived at this conclusion analyzing light from a quasar located 12.3 billion light-years away. A similar set of observations for two other quasars, together with the most precise laboratory measurements, allows scientists to infer that the ratio of the proton to electron masses may have changed with time (our last posting).

These exciting results will be available in a paper accepted for publication in the Astrophysical Journal Letters ("Molecular Hydrogen in a Damped Lyman-α system at zabs=4.224", by C. Ledoux, P. Petitjean, and R. Srianand).