Davis, R. (2010). Fundamental constants: Big G revisited Nature, 468 (7321), 181-183 DOI: 10.1038/468181b

From the abstract:

Measuring Newton’s constant of gravitation is a difficult task, because gravity is the weakest of all the fundamental forces. An experiment involving two simple pendulums provides a seemingly accurate but surprising value.

For more, see Fundamental constants: Big G revisted.

Galaxy Zoo (2010). Galaxy Zoo Supernovae arXiv arXiv: 1011.2199v2

This paper presents the first results from a new citizen science project: Galaxy Zoo Supernovae which, with 2500 volunteers, has categorized almost 14,000 supernovae candidates.

For more, see Galaxy Zoo paper goes supernova.

From the Press Release:

This composite image shows a supernova within the galaxy M100 that may contain the youngest known black hole in our cosmic neighborhood. In this image, Chandra’s X-rays are colored gold, while optical data from ESO’s Very Large Telescope are shown in red, green, and blue, and infrared data from Spitzer are red. The location of the supernova, known as SN 1979C, is labeled… This approximately 30-year age, plus its relatively close distance, makes SN 1979C the nearest example where the birth of a black hole has been observed, if the interpretation by the scientists is correct.

Sure, black holes can have finite age, that seems perfectly reasonable… well no, not really. The “age” of a black hole is an exceptionally complicated, verging on philosophical, matter that I’ll have to write about.

For more, see Black Hole Baby Spotted Being Born, Youngest nearby black hole found, Youngest Nearby Black Hole.

Andresen, G., & et al. (2010). Trapped antihydrogen Nature DOI: 10.1038/nature09610

From the abstract:

Antihydrogen, the bound state of an antiproton and a positron, has been produced

^{2, 3}at low energies at CERN (the European Organization for Nuclear Research) since 2002. Antihydrogen is of interest for use in a precision test of nature’s fundamental symmetries. … Here we demonstrate trapping of antihydrogen atoms. …This result opens the door to precision measurements on anti-atoms, which can soon be subjected to the same techniques as developed for hydrogen.

For more, see Antiatoms Bottled for First Time, Antimatter atoms held captive by physicists.

V. G. Gurzadyan, & R. Penrose (2010). Concentric circles in WMAP data may provide evidence of violent pre-Big-Bang activity arXiv arXiv: 1011.3706v1

From the abstract:

Conformal cyclic cosmology (CCC) posits the existence of an aeon preceding our Big Bang ‘B’, whose conformal infinity ‘I’ is identified, conformally, with ‘B’, now regarded as a spacelike 3-surface. Black-hole encounters, within bound galactic clusters in that previous aeon, would have the observable effect, in our CMB sky, of families of concentric circles over which the temperature variance is anomalously low, the centre of each such family representing the point of ‘I’ at which the cluster converges… These observational predictions of CCC would not be easily explained within standard inflationary cosmology.

A very interesting, and easily misinterpreted paper, co-authored by the great Roger Penrose is the major buzz of this week. It doesn’t imply anything about “before the universe” knowledge, which would be unphysical, but it does say that if we lived in a certain type of cyclic universe, with multiple contractions and expansions (initiated by “Big Bangs”) throughout its history, we might be able to see evidence of those contraction/expansion cycles in the CMB. Do we see that evidence? Maybe. Pattern matching in the CMB is able to show a lot of people a lot of different results that don’t fit in to the standard inflationary scheme, but none with a very high level of confidence. Basically, inflation isn’t quite right, we might live in a cyclic universe, but we also might not.

For more, see Penrose claims to have glimpsed universe before Big Bang, Have we found the universe that existed *before* the Big Bang? (I’ll answer that one: No).

Belgiorno, F., Cacciatori, S., Clerici, M., Gorini, V., Ortenzi, G., Rizzi, L., Rubino, E., Sala, V., & Faccio, D. (2010). Hawking Radiation from Ultrashort Laser Pulse Filaments Physical Review Letters, 105 (20) DOI: 10.1103/PhysRevLett.105.203901

Abstract:

Event horizons of astrophysical black holes and gravitational analogues have been predicted to excite the quantum vacuum and give rise to the emission of quanta, known as Hawking radiation. We experimentally create such a gravitational analogue using ultrashort laser pulse filaments and our measurements demonstrate a spontaneous emission of photons that confirms theoretical predictions.

For more, see Physicists Create Black Hole ‘Light’ in Lab, New horizons for Hawking radiation.

Alberto S. Cattaneo, & Florian Schaetz (2010). Introduction to supergeometry arXiv arXiv: 1011.3401v1

The abstract:

These notes are based on a series of lectures given by the first author at the school of `Poisson 2010′, held at IMPA, Rio de Janeiro. They contain an exposition of the theory of super- and graded manifolds, cohomological vector fields, graded symplectic structures, reduction and the AKSZ-formalism.

Benjamin Bahr, Bianca Dittrich, & Song He (2010). Coarse graining theories with gauge symmetries arXiv arXiv: 1011.3667v1

The abstract:

Discretizations of continuum theories often do not preserve the gauge symmetry content. This occurs in particular for diffeomorphism symmetry in general relativity, which leads to severe difficulties both in canonical and covariant quantization approaches. We discuss here the method of perfect actions, which attempts to restore gauge symmetries by mirroring exactly continuum physics on a lattice via a coarse graining process. Analytical results can only be obtained via a perturbative approach, for which we consider the first steps, namely the coarse graining of the linearized theory. The linearized gauge symmetries are exact also in the discretized theory, hence we develop a formalism to deal with gauge systems. Finally we provide a discretization of linearized gravity as well as a coarse graining map and show that with this choice the 3D linearized gravity action is invariant under coarse graining.

Veronika E. Hubeny (2010). The Fluid/Gravity Correspondence: a new perspective on the Membrane Paradigm arXiv arXiv: 1011.4948v1

From the abstract:

This talk gives an overview of the recently-formulated Fluid/Gravity correspondence, which was developed in the context of gauge/gravity duality. Mathematically, it posits that Einstein’s equations (with negative cosmological constant) in d+1 dimensions capture the (generalized) Navier-Stokes equations in d dimensions. Given an arbitrary fluid dynamical solution, we can systematically construct a corresponding asymptotically AdS black hole spacetime with a regular horizon whose properties mimic that of the fluid flow. Apart from an overview of this construction, we describe some of its applications. The presentation is intended for a broad audience of relativists, and does not assume prior knowledge of string theory or gauge/gravity duality.

This is just beautiful.

]]>Dan Hooper, & Lisa Goodenough (2010). Dark Matter Annihilation in The Galactic Center As Seen by the Fermi Gamma Ray Space Telescope arXiv arXiv: 1010.2752v1

Analyzing old data from the Fermi Gamma Ray Space Telescope, the authors have noticed gamma ray emissions consistent with predictions for a certain type of dark matter. Unfortunately, these things are never nice, clear problems where they’ve definitely seen dark matter or have definitely not seen it, but it’s an exciting collection of data points for astrophysicists who are on the dark matter hunt. It could turn out to be the evidence that people have been looking for, but it’s too early to say anything definitively.

For more, see Signs of Destroyed Dark Matter Found in Milky Way’s Core, Fermilab theorist sees dark matter evidence in public data.

Champion, D., et al. (2010). MEASURING THE MASS OF SOLAR SYSTEM PLANETS USING PULSAR TIMING The Astrophysical Journal, 720 (2) DOI: 10.1088/2041-8205/720/2/L201

What can’t pulsars do? The team, using an array of pulsars (PSRs J0437–4715, J1744–1134, J1857+0943, J1909–3744), have identified the masses of the planetary system from Mercury to Saturn, in agreement with the best-known masses determined by spacecraft and other observations. This new method relies on the incredibly predictable nature of pulsars and solar system ephemeris (the past and future positions of the Sun, Moon, and nine planets in three-dimensional space).

From the authors:

While spacecraft are likely to produce the most accurate measurements for individual solar system bodies, the pulsar technique is sensitive to planetary system masses and has the potential to provide the most accurate values of these masses for some planets.

Practical!

For more, see A New Way to Weigh Planets.

Poznanski, D., Nugent, P., & Filippenko, A. (2010). TYPE II-P SUPERNOVAE AS STANDARD CANDLES: THE SDSS-II SAMPLE REVISITED The Astrophysical Journal, 721 (2), 956-959 DOI: 10.1088/0004-637X/721/2/956

For years, Type Ia supernovae have been used as standard candles to measure cosmic distances; they were especially important for the measurements that determined that the expansion of the universe ws accelerating. Now, some astrophysicists are suggesting that for even higher accuracy, we use Type II supernovae as well. Initially, Type II supernovae weren’t used as standard candles because we weren’t as sure about their properties and actual brightness as we were for Type Ia supernovae. Using additional markers to gauge cosmic distances could help confirm and strengthen current observations, as well as discover inconsistencies.

Adam Burrows, astrophysicist at Princeton University:

It is unlikely that this technique will be able to compete with Ia, but it can contribute complementary cosmic information. It is coming into its own.

For more, see Alternative yardstick to measure the universe.

Lopes, I., & Silk, J. (2010). Neutrino Spectroscopy Can Probe the Dark Matter Content in the Sun Science, 330 (6003), 462-462 DOI: 10.1126/science.1196564

The abstract:

After being gravitationally captured, low-mass cold dark-matter

^{ }particles (mass range from 5 to ~50 x 10^{9}electron volts) are^{ }thought to drift to the center of the Sun and affect its internal^{ }structure. Solar neutrinos provide a way to probe the physical^{ }processes occurring in the Sun’s core. Solar neutrino^{ }spectroscopy, in particular, is expected to measure the neutrino^{ }fluxes produced in nuclear reactions in the Sun. Here, we show^{ }how the presence of dark-matter particles inside the Sun will^{ }produce unique neutrino flux distributions in^{7}Be- and^{8}B-,^{ }as well as^{13}N-,^{15}O-, and^{17}F-.

Finally, a credible sounding experiment to test this dark-matter-in-the-sun-hypothesis, discover that there is no cold dark matter in the sun, and convince people to stop taking things seriously just because they technically “could” be possible. We’re not 100% sure of the consistency of the moon either, therefore I propose it’s full of anaerobic unicorns.

For more, see Neutrino Spectroscopy Can Probe the Dark Matter Content in the Sun.

Lehnert, M., Nesvadba, N., Cuby, J., Swinbank, A., Morris, S., Clément, B., Evans, C., Bremer, M., & Basa, S. (2010). Spectroscopic confirmation of a galaxy at redshift z = 8.6 Nature, 467 (7318), 940-942 DOI: 10.1038/nature09462

Spectroscopic techniques have confirmed the sighting of a galaxy at redshift *z* = 8.6! Light from UDFy-38135539 is coming to us from 600 million years after the Big Bang, ie. z=8.6 means a light travel time of 13.1 billion years (comoving distance of around 30.5 billion light years) making it the oldest/farthest away object ever recorded. This is really exciting because we probably can not see older/farther objects with the current generation of telescopes so it could be a very long time before UDFy-38135539’s record is beaten.

*Not counting the CMB.

For more, see Oldest Object in Universe Found, Astronomy: Galaxy sets distance mark, Most distant galaxy ever found sheds light on infant cosmos.

Raphael Bousso, Ben Freivogel, Stefan Leichenauer, & Vladimir Rosenhaus (2010). Eternal inflation predicts that time will end arXiv arXiv: 1009.4698v1

Yeah, I put this story after astronomy…

Abstract:

Present treatments of eternal inflation regulate infinities by imposing a geometric cutoff. We point out that some matter systems reach the cutoff in finite time. This implies a nonzero probability for a novel type of catastrophe. According to the most successful measure proposals, our galaxy is likely to encounter the cutoff within the next 5 billion years.

Ie. if we make a series of fairly wild assumptions, we end up with a high statistical likelihood that some type of major astronomical catastrophe will occur. Unfortunately, like any incredibly complex system, small errors in initial assumptions make any sort of numerical prediction meaningless here… so, no reason to be concerned at all. The universe could end in 1 year, 5 billion years, never, etc. We have no consistent or meaningful way to predict this yet.

For more, see The universe might have to end in 3.7 billion years so that the laws of physics make sense.

The site for the $167m Indian Neutrino Observatory (INO) was approved this week by the Indian Ministry of Environment and Forests. This project will mean major things for the state of physics in India, and it will likely be the country’s largest scientific endeavour.

For more, see Green light for Indian neutrino observatory.

Sabine Hossenfelder (2010). Experimental Search for Quantum Gravity arXiv arXiv: 1010.3420v1

Physicist/blogger Sabine Hossenfelder has an interesting review piece on the phenomenological models that are used in quantum gravity as well as the experimental areas that they might be testable in. It’s a summary for those that are interested in what is being done right now in the experimental quantum gravity world.

For more, see If you’re interested in the phenomenology of quantum gravity….

Major, S. (2010). Shape in an atom of space: exploring quantum geometry phenomenology Classical and Quantum Gravity, 27 (22) DOI: 10.1088/0264-9381/27/22/225012

If the title of this paper doesn’t sound exciting to you, I don’t know what does.

The abstract:

A phenomenology for the deep spatial geometry of loop quantum gravity is introduced. In the context of a simple model of an atom of space, it is shown how purely combinatorial structures can affect observations. The angle operator is used to develop a model of angular corrections to local, continuum flat-space 3-geometries. The physical effects involve neither breaking of local Lorentz invariance nor Planck-scale suppression, but rather only rely on the combinatorics of

SU(2) recoupling. Bhabha scattering is discussed as an example of how the effects might be observationally accessible.

If you like symmetry breaking, quantization of the gravitational field, and geometry (and frankly, who doesn’t), you’ll probably enjoy this paper. It’s a fascinating study on the geometry, under some loopy assumptions, of the quantum world, and the mathematical peculiarities that effect our ability to observe it. Bonus: Seth Major also knows how to write accessibly too, for those who are field adjacent.

For more, see Shape in an atom of space: exploring quantum geometry phenomenology.

Sachdev, S. (2010). Holographic Metals and the Fractionalized Fermi Liquid Physical Review Letters, 105 (15) DOI: 10.1103/PhysRevLett.105.151602

Everyone’s favourite correspondence, the AdS/CFT correspondence, is at it again, this time, making sense of strange metals.

The abstract:

We show that there is a close correspondence between the physical properties of holographic metals near charged black holes in anti–de Sitter (AdS) space, and the fractionalized Fermi liquid phase of the lattice Anderson model. The latter phase has a “small” Fermi surface of conduction electrons, along with a spin liquid of local moments. This correspondence implies that certain mean-field gapless spin liquids are states of matter at nonzero density realizing the near-horizon, AdS

_{2}×R^{2}physics of Reissner-Nordström black holes.

This amazing correspondence could lead to a unified model for understanding strange metals (thanks to string theory) that could result in numerous calculations, that were previously too hard to tackle, being solved by techniques already known in the black hole community

For more, see String theory tackles strange metals, In pursuit of a nameless metal.

Henrique Gomes, Sean Gryb, & Tim Koslowski (2010). Einstein gravity as a 3D conformally invariant theory arXiv arXiv: 1010.2481v1

The authors have described an alternative description for the physical content/observable character of general relativity without the Lorentz invariant spacetime! Now most of you are probably thinking, “Well that sounds insane!”, and, I’d be inclined to agree, but it’s an interesting proposal. Basically, they’ve taken some ideas from Horava-Lifshitz gravity, such that the symmetries of their theory are identical to Horava-Lifshitz gravity in the high energy limit, but they’ve tried to smooth out all of the errors in the low energy limit (where Horava-Lifshitz looks nothing like general relativity). Have they made a Horava-Lifshitz-esque theory that is consistent with the physical nature of general relativity? That still remains to be seen, but it’s not obviously wrong. They’ve also provided a geometric picture, that could actually turn out to be more equivalent to the one from general relativity than expected, but it will take further study.

For more, see Einstein gravity as a 3D conformally invariant theory.

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