So I woke up this morning to several emails about a strange “Higgs sighting” at ATLAS. On a Woit’s blog, a commenter named Higgs? shared an abstract purporting observations of some 115 GeV resonance at CERN. It claims to be from an “internal note” from the ATLAS Collaboration.

Higgs? says:Internal Note

Report number ATL-COM-PHYS-2011-415

Title Observation of a γγ resonance at a mass in the vicinity of 115 GeV/c2 at ATLAS and its Higgs interpretation

Author(s)Fang, Y (-) ; Flores Castillo, L R (-) ; Wang, H (-) ; Wu, S L (University of Wisconsin-Madison)

Imprint 21 Apr 2011. – mult. p.

Subject category Detectors and Experimental Techniques

Accelerator/Facility, Experiment CERN LHC ; ATLAS

Free keywords Diphoton ; Resonance ; EWEAK ; HIGGS ; SUSY ; EXOTICS ; EGAMMA

AbstractMotivated by the result of the Higgs boson candidates at LEP with a mass of about 115~GeV/c2, the observation given in ATLAS note ATL-COM-PHYS-2010-935 (November 18, 2010) and the publication “Production of isolated Higgs particle at the Large Hadron Collider Physics” (Letters B 683 2010 354-357), we studied the γγ invariant mass distribution over the range of 80 to 150 GeV/c2. With 37.5~pb−1 data from 2010 and 26.0~pb−1 from 2011, we observe a γγ resonance around 115~GeV/c2 with a significance of 4σ. The event rate for this resonance is about thirty times larger than the expectation from Higgs to γγ in the standard model. This channel H→γγ is of great importance because the presence of new heavy particles can enhance strongly both the Higgs production cross section and the decay branching ratio. This large enhancement over the standard model rate implies that the present result is the first definitive observation of physics beyond the standard model. Exciting new physics, including new particles, may be expected to be found in the very near future.

Is this a Higgs sighting? Well, the abstract says, “the event rate…is about thirty times larger than the expectation from Higgs to γγ in the standard model” making it certainly not evidence for a Standard Model Higgs. Is it a real observation? That’s a better question at this point. Better still, is this a real note?

I don’t work with CERN, so my login doesn’t give me permission to access internal memos (in fact, I can only read the partial title “Observation of a γγ resonance at a mass”?) although others have told me that the *paper* is actually there and does claim what the abstract is presenting (although perhaps not convincingly).

One of my favourite ATLAS postdocs, Mark Tibbetts, said,

The line from the management is “This is not an official result of the ATLAS experiment.”

“Not an official result”. Hmm…

Now, the authors are a little interesting because they include Sau Lau Wu. Wu is often associated with her excitement, near the end of the LEP days, when her team thought they had observed a Higgs candidate around 114GeV/c^{2} (it was basically ruled out later). The energies being so similar here make this curious.

Another important thing to point out is that the CDF has also been focused on the H→γγ search and has seen no 115 GeV bump in their data [see Search for a Standard Model Higgs Boson Decaying Into Photons at CDF Using 7.0 fb^{-1} of Data [pdf] from April 18th, 2011]. If this sizable 115 GeV bump was being found in ATLAS data, the CDF should also have seen a hint of it, not, nothing.

At this point, I see no reason in speculating on what this [result] means. It’s a rumour. The analysis may be very limited. The data may be non-existent. And it’s not impossible that someone uploaded it to the CERN servers as a joke. If the ATLAS Collaboration were to release it themselves, then we could be excited (and if people want to start throwing around “fourth generation”, “non-Standard Higgs”, “SUSY confirmed/ruled out”, *then *it *might *be reasonable). Until there is an official statement from the collaboration, or even one of the co-authors, this is just gossip. Don’t get excited. Seriously.

For more remarks, analysis, and speculation:

- Not Even Wrong: This Week’s Rumor
- The Reference Frame: ATLAS memo: 4-sigma diphoton bump at LEP’s 115 GeV
- A Quantum Diaries Survivor: Did ATLAS Just See the Higgs
- Résonaances: Higgs in ATLAS, maybe

**Update**: April 25th, 2011: “Spokeswoman quashes Higgs particle rumor” in Nature.

]]>ATLAS’ spokeswoman Fabiola Gianotti stops short of disowning the leaked document, but tells

Naturesignals of the kind reported in the memo show up quite frequently in the course of data analysis and are later falsified after more detailed scrutiny. “Only official ATLAS results, i.e. results that have undergone all the necessary scientific checks by the Collaboration, should be taken seriously,” she says.

The *romantic* doubly-special Valentine:

The platonic BF theory Valentine:

And finally, the awkward and sexual cosmic censorship Valentine:

Happy Valentine’s Day

]]>Geneva, 31 January 2011. CERN today announced that the LHC will run through to the end of 2012 with a short technical stop at the end of 2011. The beam energy for 2011 will be 3.5 TeV. This decision, taken by CERN management following the annual planning workshop held in Chamonix last week and a report delivered today by the laboratory’s machine advisory committee, gives the LHC’s experiments a good chance of finding new physics in the next two years, before the LHC goes into a long shutdown to prepare for higher energy running starting 2014.

The LHC was previously scheduled to run to the end 2011 before going into a long technical stop necessary to prepare it for running at its full design energy of 7 TeV per beam. However, the machine’s excellent performance in its first full year of operation forced a rethink. Expected performance improvements in 2011 should increase the rate that the experiments can collect data by at least a factor of three compared to 2010. That would lead to enough data being collected this year to bring tantalising hints of new physics, if there is new physics currently within reach of the LHC operating at its current energy. However, to turn those hints into a discovery would require more data than can be delivered in one year, hence the decision to postpone the long shutdown. If there is no new physics in the energy range currently being explored by the LHC, running through 2012 will give the LHC experiments the data needed to fully explore this energy range before moving up to higher energy.

See the interview with Rolf Heuer and Steve Myers on the decision. In related news, the the LHC’s winter shutdown is almost over.

Update: For a detailed discussion on the decision, see Tommaso Dorigo‘s piece, “The LHC Will Run At 7 TeV In 2011 And 2012“.

]]>So this isn’t physics*, but if you squint hard enough, you can probably make a connection. The hot topic today is Ken Ono‘s latest work on the partition function:

Ken Ono, Amanda Folsom, & Zach Kent (2011). l-adic properties of the partition function American Institute of Mathematics.

Ken Ono & *Jan Bruinier* (2011). AN ALGEBRAIC FORMULA FOR THE PARTITION FUNCTION American Institute of Mathematics.

*A **EurekAlert *press release appeared today, entitled: New math theories reveal the nature of numbers and people are already whispering *“Fields Medal”.* Now, I haven’t thoroughly read the paper yet, but, since I’m not a number theorist, my commentary probably won’t change very much anyway. Obviously, like most press releases, this one is full of hyperbole and ridiculous sentences like, “the team was determined go beyond mere theories”, but the actual work being discussed is fascinating.

Now, when we talk about a partition function in the context of Ono’s work, we don’t mean the partition function that is familiar to most physicists, we mean what number theorists call a partition function.

In this setting, a *partition *is a way of representing a natural number [latex]n[/latex] as the sum of natural numbers (ie. for [latex]n = 3[/latex], we have three partitions, [latex]3[/latex], [latex]2 + 1[/latex], and [latex]1 + 1 + 1[/latex], independent of order). Thus, the *partition function*, [latex]p(n)[/latex], represents the number of possible partitions of [latex]n[/latex]. So, [latex]p(3) = 3[/latex], [latex]p(4) = 5[/latex] (for [latex]n = 4[/latex], we have: [latex]4[/latex], [latex]3 + 1[/latex], [latex]2 + 2[/latex], [latex]2 + 1 + 1[/latex], [latex]1 + 1 + 1 + 1[/latex]) , etc..

To be slightly more technical, from Ken Ono and Kathrin Bringman [1],

A partition of a non-negative integer n is a non-increasing sequence of positive integers whose sum is [latex]n[/latex].

The concept is straight forward, but how to obtain these partition numbers, in general, is actually no trivial matter.

The master of series, Leonhard Euler, worked on solving this problem, to less than fully satisfying results. Using the reciprocal of what is now called Euler’s function, we get the generator for [latex]p(n)[/latex] by this infinite product,

[latex]\sum_{n=0}^{\infty} p(n)q^n= \prod_{n=1}^{\infty}\frac{1}{1-q^n}[/latex].

Here, [latex]q^n[/latex] counts the number of ways to write, [latex]n = a_1 + 2a_2 + 3a_3 +\ldots[/latex], for [latex]a_i \in \mathbb{N}[/latex], where each number [latex]i[/latex] appears [latex]a_i[/latex] times.

Obviously, for large [latex]n[/latex], this can be unwieldy, and it doesn’t lead to an explicit formula, but as long as you didn’t need more than 200~ partition numbers, it was *okay*.

Mathematics had to wait until the early 1900s before anyone was to expand on Euler’s partition number generator, when Srinivasa Ramanujan made contact with G.H. Hardy. Ken Ono actually has a beautiful historical, and mathematical, account of the Ramanujan and Hardy story, called “The Last Words of a Genius” [pdf].

Ramanujan famously proved an unusual and surprising result that [2],

[latex]p(5n + 4) = 0 (mod 5)[/latex],

[latex]p(7n + 5) = 0 (mod 7)[/latex],

[latex]p(11n + 6) = 0 (mod 11)[/latex].

He was also responsible for the first attempt at an explicit, although not exact, formula for [latex]p(n)[/latex] with Hardy,

[latex]p(n)\sim\frac{exp(\pi\sqrt{2n/3})}{4n\sqrt{3}}[/latex] as [latex]n \rightarrow \infty[/latex].

A decade later, Hans Rademacher came up with an exact formula, involving a convergent series, Dedekind eta functions, and Farey sequences; it was computationally unpleasant, to say the least (and not worth TeXing in here, but see Wikipedia if interested). It was also not *substantially *more useful than Euler’s initial work (although more direct).

In 2007, Ono was an author of a paper [1] that provided an arithmetic reformulation of Rademacher’s formula, using a Maass–Poincaré series. Based on some discussion, it wasn’t a giant improvement over Rademacher work.

It seems that since Euler initially came up with his generating function, there haven’t been major leaps in our understanding of partition numbers.

Apparently that all changes tomorrow. Ken Ono and colleagues, Jan Bruinier, Amanda Folsom and Zach Kent, will be announcing results that include a finite, algebraic formula for partition numbers thanks to the discovering that partitions are *fractal. *Well, so what does this mean, for partition numbers to be fractal?

Ken Ono, in the press release:

The sequences are all eventually periodic, and they repeat themselves over and over at precise intervals.

Alright, so obviously without going deeply into paper we can’t go further here (check out the pdf), but one can see how this insight could make the generation of partitions simple and explicit. This also, apparently, explains, and is linked to, Ramanujan’s *congruences* above. How? Well, they’re part of this *pattern*.

Ken Ono, in the press release:

I can take any number, plug it into P, and instantly calculate the partitions of that number. P does not return gruesome numbers with infinitely many decimal places. It’s the finite, algebraic formula that we have all been looking for.

Cool.

There is already an extension on the Ono-Folsom-Kent fractal issue by John Webb called, “An improved “zoom rate” for the Folsom-Kent-Ono l-adic fractal behavior of partition values” [pdf here].

*The physics tie in? Alright, so this is reaching, but here we go. Partitions are visualized using Young tableaus, and anyone in particle physics (see pdf for relevant introduction) has probably come across this, as well as other forms of group representation theory. Could an ability to always explicitly write down partition numbers translate to physics? I couldn’t ever imagine using groups so large that this could at all come into play… but, one could possibly draw some *conclusions* about the *fractal* nature of… ah, I give up.

Update: Comments on connections to actual physics can be found here.

[1] KATHRIN BRINGMANN, & KEN ONO (2007). An arithmetic formula for the partition function Proceedings of the American Mathematical Society, 135, 3507-3514

[2]Ken Ono (2010). The Last Words of a Genius Notices of the American Mathematical Society, 57, 1410-1419

[3] Folsom A, & Ono K (2008). The spt-function of Andrews. Proceedings of the National Academy of Sciences of the United States of America, 105 (51), 20152-6 PMID: 19091951

[4]Ken Ono, & Jan H. Bruinier (2009). Identities and congruences for the coefficients of Ramanujan’s omega(q) Ramanujan Journal

]]>So today on Twitter, Lisa Randall *tweeted* that we’ll be saying good-bye to the Tevatron this year. Currently, no statement from the DOE or Fermilab has gone out publicly confirming this, however, but, it’s very likely to be true. The rumour has been floating around for awhile, but researchers were still holding out for additional funding to push the project into 2012 and beyond. Those at ISP220 today, say that it was announced to them that the DOE had denied further funding, and that the Tevatron wouldn’t see operations past the end of 2011.

See Chip Brock‘s *tweet* for example:

I’m sure we’ll all be pouring a drink for the Tevatron this year.

*Official* news from the Tevatron, they’ll be shutdown by October 1st, 2011. Still no announcement from Fermilab Today.

There is now a letter from the DOE, dated January 6th, 2011, explaining why funding for the Tevatron could not be continued. See the pdf of the letter from the Department of Energy here or read it here:

Professor Melyn Shochet Chairman, High Energy Physics Advisory Panel Department of Physics University of Chicago 5630 S. Ellis Ave Chicago, IL 60637Dear Professor Shochet:

I am writing to convey the Office of Science’s response to the recent High Energy Physics Advisory Panel (HEPAP) report on extending the operation of the Tevatron at Fermi National Accelerator Laboratory. As you know the Office of Science received in the summer of 2010 a widely supported proposal to extend operation of the Tevatron through FY 2014. At our request, HEPAP and its subpanel, Particle Physics Project Prioritization Panel (P5), responded quickly and analzed both the physics merits of the proposal and the potential impacts on the rest of the field. HEPAP and P5 provided valuable and timely advice to the Office of Science that informed our FY 2012 budget request. I thank HEPAP and P5 for these efforts.

In summary, P5 found the proposed physics program had significant scientific value and would complement what can be accomplished at the Large Hadron Collider (LHC) in the same time period, but recognized that without additional funding the extension of Tevatron operations would delay progress on the development of the Intensity Frontier program by HEP. P5 therefore recommended that extension of the operation of the Tevatron be approved only if additional funds were available to HEP, and encouraged the funding agencies to find the necessary resources. Unfortunately, the current budgetary climate is very challenging and additional funding has not been identified. Therefore, based in part on the P5 recommendation, operation of the Tevatron will end in FY 2011, as originally scheduled.

The strategic plan for the US particle physics program, developed by P5, attacks the most important scientific questions in three broad areas of the field: the Energy, Intensity, and Cosmic Frontiers. The Energy Frontier has passed to the LHC, where the first year of data collection recently was completed. Accelerator performance at the LHC improved dramatically during 2010, achieving increases of several orders of magnitude in instantaneous luminosity. U.S. Scientists play a major role in the ATLAS and CMS collaborations at the LHC, with both experiments publishing early physics results that clearly demonstrate the impressive capabilities of these detectors. Given the LHC performance to date, it appears likely that experiments at the LHC either will rule out or discover a standard model Higgs boson by late 2012, addressing this pressing topic in particle physics in a timely manner. Support for activities at the LHC continues to have high priority in the HEP program.

The HEP program also calls for a world-leading program centred at FNAL to probe the Standard Model using a complementary approach of high intensity beams. This program aims to measure the fundamental properties of neutrinos and to develop a new high intensity proton source. In evaluating the proposed Tevatron extension, the P5 committee emphasized the importance of developing this Intensity Frontier program and we have made implementation of this program a cornerstone of future HEP activities.

In conclusion, I want to personally thank you and the members of HEPAP and P5 for your prompt and thoughtful response to our request for advice.

Sincerely yours,

W.F. Brinkman Director, Office of Science U.S. Department of Energy

There are no surprises here, although it’s sad to see the end of an era.

Symmetry Magazine has a letter from Fermilab Director Pier Oddone to the community on the news. “While we would have liked to run the Tevatron for three more years, our life going forward is full of promising projects and great opportunities for major discoveries.”

**Yes, Twitter is how this story came about.*

From *The Language of Bad Physics*

Other Seasonal Gems* *

- From
*Starts with a Bang*: Hubble for the Holidays: A Bauble of a Bubble - From
*Starts with a Bang*: Hubble for the Holidays: Have a Cigar! - From
*Starts with a Bang*: Hubble for the Holidays: Eta Carinae - From
*sciencebase*: A Lethal Christmas Star *Physics World*reveals its top 10 breakthroughs for 2010- From
*Wikipedia:*Physics/2010 Selected pictures

Papers on the *arXiv*

Classics

- From
*Wesleyan Department of Physics*: Physics Carols - The Physics of Christmas
- [0503069] Images in Christmas Balls

Belated-Christmas Present Ideas

- Still trying to find your GravityGeek a Present for Newton’s Birthday?
- ESVA 2011 Calendar ‘Physicists at Work & Play’
- The Physics of Christmas: From the Aerodynamics of Reindeer to the Thermodynamics of Turkey

]]>

I’m not going to call these the best papers, or the most cited (although some of them are), but they all contain things that were interesting or unique that encouraged further work and discussion (even if myself and others disagreed with the results) and thus, they got gingerbread cookies baked in their honour. So without further ado, these are the 10 cookies highlights from 2010 literature in general relativity, quantum gravity, and gravitation (ranked by date of e-print, so don’t read into the order):

Yun Soo Myung, & Yong-Wan Kim (2010). Thermodynamics of *Hořava*-Lifshitz black holes. Eur.Phys.J. C68 (2010) 265-270 arXiv: 0905.0179v3

We study black holes in the Ho

řava-Lifshitz gravity with a parameter λ. For 1/3≤ λ < 3, the black holes behave the Lifshitz black holes with dynamical exponent 0 < z ≤ 4, while for λ > 3, the black holes behave the Reissner-Nordstr¨om type black hole in asymptotically flat spacetimes. Hence, these all are quite different from the Schwarzschild-AdS black hole of Einstein gravity. The temperature, mass, entropy, and heat capacity are derived for investigating thermodynamic properties of these black holes.

Using this first law [of thermodynamics], we derive an entropy…

So, obviously a *Hořava*-Lifshitz gravity paper was a must for 2010, but selecting which one was difficult. While this paper was technically written in 2009, it was baked published in the *European Physical Journal* in 2010 (and it was in 2010 that it was really being discussed). Cited, approximately 95 times, it’s clearly on the more delicious side of *Hořava*-Lifshitz.

Asimina Arvanitaki, Savas Dimopoulos, Sergei Dubovsky, Nemanja Kaloper, & John March-Russell (2009). String Axiverse Phys.Rev. D, 81 arXiv: 0905.4720v2

String theory suggests the simultaneous presence of many ultralight axions possibly populating each decade of mass down to the Hubble scale 10⁻³³eV. Conversely the presence of such a plenitude of axions (an ‘axiverse’) would be evidence for string theory, since it arises due to the topological complexity of the extra-dimensional manifold and is ad hoc in a theory with just the four familiar dimensions. We investigate how upcoming astrophysical experiments will explore the existence of such axions over a vast mass range… The rapidly rotating black hole in the X-ray binary LMC X-1 implies an upper limit on the decay constant of the QCD axion fₐ ≤ 2 x 10¹⁷ GeV, much below the Planck mass…

Testing stringy ideas with astrophysics! At 42 pages and a respectable 35 citations, I choose this paper as one of the most enjoyable from 2010 because it presents a fairly abstract idea with a clever way to test it. One of the hardest tasks in theoretical physics, especially in quantum gravity, is to figure out recipes observations that would uniquely confirm your ideas, and that’s basically what this team has done.

Erik P. Verlinde (2010). On the Origin of Gravity and the Laws of Newton arXiv arXiv: 1001.0785v1

Starting from first principles and general assumptions Newton’s law of gravitation is shown to arise naturally and unavoidably in a theory in which space is emergent through a holographic scenario. Gravity is explained as an entropic force caused by changes in the information associated with the positions of material bodies. A relativistic generalization of the presented arguments directly leads to the Einstein equations. When space is emergent even Newton’s law of inertia needs to be explained. The equivalence principle leads us to conclude that it is actually this law of inertia whose origin is entropic.

When a particle has an entropic reason to be on one side of the membrane and the membrane carries a temperature, it will experience an eeffective force equal to

This is the entropic force.

I’m sure some can guess how it pains me to bake this one, but Verlinde certainly got a lot of people talking about new ideas, and spawned a lot of publications by other researchers in 2010 (132 citations and counting). For that unsatisfied taste left in your mouth after the above, try Padmanabhan’s “Surface Density of Spacetime Degrees of Freedom from Equipartition Law in theories of Gravity” 1003.5665v2.

E. Komatsu, et al. (2010). Seven-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Interpretation arXiv arXiv: 1001.4538v3 (see also: *There Cosmic Microwave Background Anomalies?* 1001.4758v1)

The 7-year WMAP data and improved astrophysical data rigorously test the standard cosmological model and its extensions. By combining WMAP with the latest distance measurements from BAO and H0 measurement, we determine the parameters of the simplest LCDM model. …

Now while this is certainly on the observational side of things, seeing as it was the culmination of a huge experiment, profoundly critical to cosmology, it seemed well worth to include in a 2010 list (the 635 citations this year also suggest that). The prep. time was well worth the results here.

Gary T. Horowitz (2010). Introduction to Holographic Superconductors arXiv arXiv: 1002.1722v2

These lectures give an introduction to the theory of holographic superconductors. These are superconductors that have a dual gravitational description using gauge/gravity duality. After introducing a suitable gravitational theory, we discuss its properties in various regimes: the probe limit, the effects of backreaction, the zero temperature limit, and the addition of magnetic fields. Using the gauge/gravity dictionary, these properties reproduce many of the standard features of superconductors. …

The gauge/gravity dictionary says that the retarded Green’s function (for Jx) in the dual field theory is

So this one is a little different than the above, as it doesn’t really present a new result, but it is, in fact a mini lecture series on a hot new topic. Why did I choose this instead of one of the papers it cited, perhaps? Well, because Horowitz sets out the ingredients better than almost anybody else. In terms of clear pieces of literature written on the amazing beauty that is the AdS/CFT correspondence, this has got to be one of the best from 2010 (and it has been cited 64 times by those who hungrily agree).

Antonio De Felice, & Shinji Tsujikawa (2010). f(R) theories Living Rev. Rel. 13: 3, 2010 arXiv: 1002.4928v2

Over the past decade, f(R) theories have been extensively studied as one of the simplest modifications to General Relativity. In this article we review various applications of f(R) theories to cosmology and gravity – such as inflation, dark energy, local gravity constraints, cosmological perturbations, and spherically symmetric solutions in weak and strong gravitational backgrounds. We present a number of ways to distinguish those theories from General Relativity observationally and experimentally. We also discuss the extension to other modified gravity theories such as Brans-Dicke theory and Gauss-Bonnet gravity, and address models that can satisfy both cosmological and local gravity constraints.

We start with the 4-dimensional action in f (R) gravity:

where κ² = 8πG, g is the determinant of the metric gμν, and LM is a matter Lagrangian1 that depends on gμν and matter fields ΨM.

Now this is another review paper (verging on “cook book”), but it is also a distinctly tasty one (cited 102 times so far). If you wanted *the* resource on f(R) theories of gravity, you’re in luck because it was written this year.

Carlo Rovelli, & Matteo Smerlak (2010). Thermal time and the Tolman-Ehrenfest effect: temperature as the “speed of time” arXiv arXiv: 1005.2985v3

The thermal time hypothesis has been introduced as a possible basis for a fully general-relativistic thermodynamics. Here we use the notion of thermal time to study thermal equilibrium on stationary spacetimes. Notably, we show that the Tolman-Ehrenfest effect (the variation of temperature in space so that Tgₒₒ⁻½ remains constant) can be reappraised as a manifestation of this fact: at thermal equilibrium, temperature is locally the rate of flow of thermal time with respect to proper time – pictorially, “the speed of (thermal) time”. Our derivation of the Tolman-Ehrenfest effect makes no reference to the physical mechanisms underlying thermalization, thus illustrating the import of the notion of thermal time.

Given a statistical state ρ, we define the thermal time flow α :

A→Aas the Poisson flow of (−ln ρ) inA. That is

where the r.h.s. is the Poisson bracket.

Short and sweet (and currently only cited two times, not that that stops me from including it), Rovelli and Smerlak bring thermal time to stationary spacetimes. “Thermal time” is a catchy idea that is supposed to help general relativity and quantum mechanics blend with thermodynamics. Not only could these ideas be important for the unification of general relativity, quantum effects and thermodynamics, but they also play an important role in the *nature of time* debate. This is a paper that has serious rising potential.

Steven Carlip (2010). The Small Scale Structure of Spacetime arXiv arXiv: 1009.1136v1

Several lines of evidence hint that quantum gravity at very small distances may be effectively two-dimensional. I summarize the evidence for such “spontaneous dimensional reduction,” and suggest an additional argument coming from the strong-coupling limit of the Wheeler-DeWitt equation. If this description proves to be correct, it suggests a fascinating relationship between small-scale quantum spacetime and the behavior of cosmologies near an asymptotically silent singularity.

For a scalar field, in particular, the propagator is determined by the heat kernel, and the behavior of the spectral dimension implies a structure

This is one of my favourites from the year; there is a lot of elegant physics contained within these pages (and yet still only two citations). Understanding the small scale structure of spacetime is going to be a major part of physics for the next few decades (at least), and coming at spontaneous dimensional reduction from CDT is a decent looking approach. Some of the delicious ideas discussed by Carlip may very well prove to be the base for our future understanding of a quantum spacetime.

Eugenio Bianchi (2010). Black Hole Entropy, Loop Gravity, and Polymer Physics arXiv arXiv: 1011.5628v1

Loop Gravity provides a microscopic derivation of Black Hole entropy. In this paper, I show that the microstates counted admit a semiclassical description in terms of shapes of a tessellated horizon. The counting of microstates and the computation of the entropy can be done via a mapping to an equivalent statistical mechanical problem: the counting of conformations of a closed polymer chain. This correspondence suggests a number of intriguing relations between the thermodynamics of Black Holes and the physics of polymers.

In particular, in the slowly rotating case, Smarr formula applies: the dependence of the entropy on the angular momentum is quadratic and given by

This was another paper that I really enjoyed recently; it’s hard not to find these correspondences staggeringly beautiful, honestly. While approaches combining polymer physics techniques with general relativity don’t have a big following yet, they’re definitely one of *the* growing ideas in LQG from 2010. Loop quantum gravity and polymer physics are just heating up the kitchen; we haven’t even see what they’ll really be making yet.

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

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 centres appear as fairly randomly distributed fixed points in our CMB sky. The analysis of Wilkinson Microwave Background Probe’s (WMAP) cosmic microwave background 7-year maps does indeed reveal such concentric circles, of up to 6 σ significance. This is confirmed when the same analysis is applied to BOOMERanG98 data, eliminating the possibility of an instrumental cause for the effects. These observational predictions of CCC would not be easily explained within standard inflationary cosmology.

It’s everyone’s favourite topic this month: Penrose and Gurzadyan’s “evidence”* *for a cyclic cosmological model. Sure, they’re probably wrong, but come on, it’s Christmas! (expect the citation count to grow on this one steadily into the new year), plus, who doesn’t still get a little excited when Roger Penrose puts that apron on (*… wait… what?*).

_________________

Overarching themes: I did intentionally choose papers that were published on the arXiv (so they could be accessed from anywhere/by anyone), but that criteria didn’t actually affect my selections (as really, what from 2010 wasn’t on the arXiv?). Yes, yes, it was a little light on string theory topics, but that could very well be because more exciting things are happening elsewhere (or because I’m not all that stringy).

Note: Citation counts are only approximate and from the time that I am writing this post, of course.

And Another Note: The cookies start changing colour part way through because my second batch of dough was made with a different colour molasses. Also, the order they were made in correlates to how nice they look, as it was tiring.

Further Note: If any of the authors want their cookies… they’ll have probably been eaten already, but if you email me quickly, I’m willing to send them to you (or if you know me, just ask and I’ll make you some for whenever we’ll be running into each other next).

So, as it’s now finally starting to look like winter here (and I have actual work piling up like snow), I felt it was appropriate to get a little festive, and thus you get,

On the first day of Christmas,

My PI gave to me:

A pile of papers to read.

On the second day of Christmas,

My PI gave to me:

2 data sets,

And a pile of papers to read.

On the third day of Christmas,

My PI gave to me:

3 rejected drafts,

2 data sets,

And a pile of papers to read.

On the fourth day of Christmas,

My PI gave to me:

4 re-vi-sions,

3 rejected drafts,

2 data sets,

And a pile of papers to read.

On the fifth day of Christmas,

My PI gave to me:

Five Ci-ta-tions…

4 revisions,

3 rejected drafts,

2 data sets,

And a pile of papers to read.

On the sixth day of Christmas,

My PI gave to me:

6 cups of coffee,

Five Citations…

4 revisions,

3 rejected drafts,

2 data sets,

And a pile of papers to read.

On the seventh day of Christmas,

My PI gave to me:

7 courses to mark,

6 cups of coffee,

Five Citations…

4 revisions,

3 rejected drafts,

2 data sets,

And a pile of papers to read.

On the eight day of Christmas,

My PI gave to me:

8 grant proposals,

7 courses to mark,

6 cups of coffee,

Five Citations…

4 revisions,

3 rejected drafts,

2 data sets,

And a pile of papers to read.

On the ninth day of Christmas,

My PI gave to me:

9 hours of coding,

8 grant proposals,

7 courses to mark,

6 cups of coffee,

Five Citations…

4 revisions,

3 rejected drafts,

2 data sets,

And a pile of papers to read.

On the tenth day of Christmas,

My PI gave to me:

10 syntax errors,

9 hours of coding,

8 grant proposals,

7 courses to mark,

6 cups of coffee,

Five Citations…

4 revisions,

3 rejected drafts,

2 data sets,

And a pile of papers to read.

On the eleventh day of Christmas,

My PI gave to me:

11 infinite loops,

10 syntax errors,

9 hours of coding,

8 grant proposals,

7 courses to mark,

6 cups of coffee,

Five Citations…

4 revisions,

3 rejected drafts,

2 data sets,

And a pile of papers to read.

On the twelfth day of Christmas,

My PI gave to me:

12 reference letters,

11 infinite loops,

10 syntax errors,

9 hours of coding,

8 grant proposals,

7 courses to mark,

6 cups of coffee,

Five Citations…

4 revisions,

3 rejected drafts,

2 data sets,

And a pile of papers to read.

I strongly encourage people to actually sing this; especially if they record it and send it to me.

UPDATE: Keeping the holiday things together, I link to Christmas Newton’s Birthday Suggestions for a Relativist.

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