Search Talks

In this talk I will describe how to calculate the exact partition function for free bosons on the plane with lacunae using world line effective field theory. It will be shown that the partition function for a plane with two spherical holes can be calculated by matching exactly for the infinite set of Wilson coefficients and then performing the ensuing Gaussian integration. This same partition function can also be calculated using conformal field theory technique and the equality of the two results will be shown. I will demonstrate that there is an exact correspondence between the Wilson coefficients (susceptabilities) in the effective field theory and the weights of the individual excitations of the closed string coherent state on the boundary. The partition function for the case of three holes, where CFT techniques necessitate a closed form for the map from the corresponding closed string pants diagram, is still calculable within the EFT. I will also show how conformal mappings can be used within the matching procedure to calculate the partition function for elliptically shaped boundaries. Finally I will show that the Wilson coefficients for the case of quartic and higher order kernels, where standard CFT techniques are no longer applicable, can also be completely determined.

Using an approach originally developed to study gravitational wave absorption in black hole binary systems, we generalize the EFT of single clock inflation to include dissipative effects. We restrict ourselves to situations where the degrees of freedom responsible for dissipation do no contribute to the density perturbations at late time, and moreover they are predominately sensitive to the field whose fluctuations control the end of inflation. The dynamics of the perturbations is then modified by the appearance of `friction' and noise terms, and assuming certain locality properties we show that there is a regime, characterized by a large friction coefficient \gamma >> H, in which the power spectrum is dominated by the noise and it is significantly modified with respect to the Bunch-Davies result. Furthermore, the non-linear realization of the symmetries implies non-gaussianties which are enhanced with respect to single clock models without dissipation by a factor of \gamma/H, and whose shape functions can in principle be distinguished from those obtained in the Bunch-Davies vacuum. We also discuss the matching of the EFT with a few key examples such as trapped and warm inflation.

It's usually assumed that youtube is just for kittens, babies, and music videos. However, youtube is also the highest-traffic site on the internet and it turns out it's actually a darn good place to teach people about physics! We'll start with the story and analysis of how my video series Minutephysics grew from a fun project to a youtube channel with 120,000 subscribers and 9 million views in just a few months, then discuss how media & technology (especially videos) can facilitate good (and bad) communication, and finally talk about how you can harness the power of the internet in your own physics outreach. And of course we'll watch a few cool videos along the way. As a primer, feel free to check out www.youtube.com/minutephysics

The experimental violation of Bell inequalities using spacelike separated measurements precludes the explanation of quantum correlations through causal influences propagating at subluminal speed. Yet, it is always possible, in principle, to explain such experimental violations through models based on hidden influences propagating at a finite speed v>c, provided v is large enough. Here, we show that for any finite speed v>c, such models predict correlations that can be exploited for faster-than-light communication. This superluminal communication does not require access to any hidden physical quantities, but only the manipulation of measurement devices at the level of our present-day description of quantum experiments. Hence, assuming the impossibility of using quantum non-locality for superluminal communication, we exclude any possible explanation of quantum correlations in term of finite-speed influences.

The Effective Field Theory (EFT) approach can be employed to perform high PN order calculations of the Hamiltonian of a binary system. We show how we reproduced the 3PN dynamics by means of an algorithm implemented in Mathematica and our progress towards the computation of the 4PN Hamiltonian. We also show the EFT computation of the tail term affecting the conservative dynamics at 4PN order, first derived using traditional methods by Blanchet and Damour.

We consider the effect of an in-plane current on the magnetization dynamics of a quasi-two-dimensional spin-orbit coupled nanoscale itinerant ferromagnet. By solving the appropriate kinetic equation for an itinerant electron ferromagnet, we show that Rashba spin-orbit interaction provides transport currents with a switching action, as observed in a recent experiment (I. M. Miron et al., Nature 476, 189 (2011)). The dependence of the effective switching field on the magnitude and direction of an external magnetic field in our theory agrees well with experiment.

The partition function on the three-sphere of many supersymmetric Chern-Simons-matter theories reduces, by localization, to a matrix model. In this talk I will describe a new method to study these models in the M-theory limit, but at all orders in the 1/N expansion. The method is based on reformulating the matrix model as the partition function of a Fermi gas. This new approach leads to a completely elementary derivation of the N^{3/2} behavior for ABJM theory and other quiver Chern-Simons-matter theories. In addition, the full series of 1/N corrections to the original matrix integral can be simply determined by a next-to-leading calculation in the semiclassical expansion of the quantum gas.