Sourya Ray completed his PhD at UMass under the supervision of Jennie Traschen and myself in 2008. After graduating, Sourya moved on to a postdoctoral research position with the excellent gravity theory group at the Centro de Estudios Cientificos (CECs) in Valdivia, Chile. This went quite well and I’m happy to report that Sourya has now begun a faculty position at the Universidad Austral de Chile which is located just down the street from the CECs in Valdivia.
I am happy to be serving for this academic year as Interim Director of the BDIC Program. BDIC (stands for Bachelor’s Degree with Individualized Concentration) is a program that allows UMass undergraduates to design their own individualized, interdisciplinary majors. Roughly 80-100 BDIC students graduate each year with concentrations spread all over the academic map (and possibly somewhat beyond).
I have been working for a number of years in BDIC as a faculty supervisor, advising students and evaluating proposed concentrations. My specialty has been working with students in the sciences and with orientations towards sustainability.
It has been known since the 1980′s that black strings are unstable to long wavelength perturbations. However, it is difficult to establish what the end point of this instability is. Similarly, it is expected that for Kaluza-Klein black holes – e.g. where one spacetime dimension is wrapped around a circle – that there would be a phase transition between localized black holes and black strings as the size of the compact dimension is decreased. Lorenzo Sorbo, Jennie Traschen and I tried to study this transition in a dynamical setting by employing the “Kastor-Traschen” space times. These are multi-black hole solutions in a deSitter background.
We considered a one-dimensional array of such black holes, which is equivalent to wrapping one dimension on a circle, in the collapsing phase of deSitter. We studied the evolution of black hole and deSitter apparent horizons. We expected to find that as the universe shrank that the black hole horizons would merge into a black string.
However, we found instead that the black hole horizons stay separate, which turned out to be a good thing. There turns out to be no non-singular charged deSitter black string for them to merge into. The actual outcome is then in accordance with cosmic censorship. We call this the “Clayton Effect” – after the Clayton Antitrust act which prohibits mergers that are antithetical to the public good!
Jennie Traschen, Sourya Ray and I posted a new paper – The Mass and Free Energy of Lovelock Black Holes – recently. Static Lovelock black holes can be thought of as “semi-unknown” solutions. The metric functions are known in terms of solutions to a polynomial equation of order [D-1/2], where D is the spacetime dimension and the brackets mean taking the integer part. For equations beyond 2nd order, it is cumbersome or not possible to write them down in closed form. Continue reading ›
UMass graduate student Ben Ett and I recently submitted a paper with the above title to the arXiv.
The basic idea is the following. Lovelock gravity is a natural higher derivative extension of Einstein gravity in higher dimensions. Static Lovelock black hole solutions have been known since the 1980′s and have appeared in many different contexts, including most recently AdS/CFT. Continue reading ›
My HEP bag lunch talk on March 8th this semester was a very speculative one, exploring possible connections between cosmic censorship and computational complexity theory. The basic idea is that extreme spacetimes, such as those with naked singularities or perhaps those with closed timelike curves, may offer special computational amenities. Perhaps the boundaries between computational complexity classes can be transgressed precisely when spacetime pathologies occur. I assembled and reviewed various results in the literature that bear on these questions.
The AdS/CFT conjecture relates a quantum field theory in a given dimension to gravitational physics in one dimension higher. Strong coupling QFT phenomena can be descried by classical general relativity. My bag lunch talk on “holographic superconductors” is an introduction to approaches to extending AdS/CFT to systems relevant in condensed matter physics.
Jennie Traschen, Sourya Ray and I have written a number of papers (here, here and here) in the past few years looking at certain types of black hole thermodynamic relations – Smarr formulas and related extensions of the first law – in a wider class of theories. Continue reading ›
Talk from our Tuesday high energy physics bag lunch series introducing the physics of black holes in higher dimensions – why is this interesting? how is it different than D=4?
