* Astronomy

 In the standard model of cosmology, the early universe underwent a period of fantastic growth. This inflationary phase, after only a trillionth of a second, concluded with a violent conversion of energy into hot matter and radiation. This "reheating" process also resulted in a flood of gravitational waves. (Interestingly, some cosmologists would identify the "big bang" with this moment and not the earlier time=0 moment.)
Let's compare this gravitational wave background (GWB) with the more familiar cosmic microwave background (CMB). The GWB dates from the trillionth-of-a-second mark, while the CMB sets in around 380,000 years later when the first atoms formed. The CMB represents a single splash of photons which were (at that early time) in equilibrium with the surrounding atoms-in-the-making; the microwaves we now see in the sky were (before being redshifted to lower frequencies owing to the universe's expansion) ultraviolet waves and were suddenly freed to travel unimpeded through space. They are now observed to be mostly at a uniform temperature of about 3 degrees Kelvin, but the overall map of the microwave sky does bear the faint imprint of matter inhomogeneities (lumps) existing even then.
What, by contrast, does the GWB represent? It stems from three different production processes at work in the inflationary era: waves stemming from the inflationary expansion of space itself; waves from the collision of bubble-like clumps of new matter at reheating after inflation; and waves from the turbulent fluid mixing of the early pools of matter and radiation, before equilibrium among them (known as thermalisation) had been achieved. The gravity waves would never have been in equilibrium with the matter (since gravity is such a weak force there wouldn't be time to mingle adequately); consequently the GWB will not appear to a viewer now to be at a single overall temperature.

A new paper by Juan Garcia-Bellido and Daniel Figueroa (Universidad Autonoma de Madrid) explain how these separate processes could be detected and differentiated in modern detectors set up to see gravity waves, such as LIGO, LISA, or BBO (Big Bang Observer). First, the GWB would be redshifted, like the CMB. But because of the GWB's earlier provenance, the reshifting would be even more dramatic: the energy (and frequency) of the waves would be downshifted by 24 orders of magnitude. Second, the GWB waves would be distinct from gravity waves from point sources (such as the collision of two black holes) since such an encounter would release waves with a sharper spectral signal. By contrast the GWB from reheating after inflation would have a much broader spectrum, centred around 1 hertz to 1 gigahertz depending on the scale of inflation.

Source

Title: Probing trans-Planckian physics and the curvature effect from primordial power spectrum with WMAP 3 observations
Authors: Jie Ren, Hong-Guang Zhang, Xin-He Meng
(revised v2)

In this work the vacuum inflation with a boundary condition specified at a short-distance scale in a generally primeval non-flat Universe, and implications of the correspondingly modified primordial power spectrum via the WMAP three year data are investigated. We obtain a general form of the modified primordial power spectrum including the effects of both possibly new physics and the curvature term. The modulation of the primordial power spectrum due to new physics is of the order H/\Lambda, where H is the Hubble parameter during inflation and \Lambda is the new physics scale that is key to inflation, while the modulation from the curvature term is of the order K/k², where K is the space curvature before inflation and k is the comoving wave number. We add two more parameters, which describe the effects from new physics scale and the curvature term respectively, into the six-parameter standard model of cosmology and make a fitting analysis with the WMAP data sets. The result shows that new physics would appear around the GUT scale and a closed Universe before inflation is slightly favoured by the data fittings.

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Controversy abounds over how to explain the highest-energy cosmic rays, subatomic particles that tear through space at near light speed while packing the punch of rifle bullets. Now a cosmic ray detector in Utah has further deepened the controversy with evidence that the particles may not be so powerful after all.
A new analysis of results from the High Resolution Fly's Eye (HiRes) experiment in Salt Lake City has detected a sharp cut-off in the energy spectrum of cosmic rays. This stands in stark contrast to a Japanese experiment that has previously reported particles with bafflingly higher energies.
According to standard physics, cosmic rays with energies larger than about 5 × 10^19 electronvolts will collide with photons left over from the big bang and so lose energy as they cross large distances. This puts a theoretical limit on the energy they can have when they reach Earth

Source

Two US scientists, John C Mather and George F Smoot, have won the 2006 Nobel Physics Prize.

They have been honoured "for their discovery of the blackbody form and anisotropy of the cosmic microwave background radiation (CMB)".

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