Past Events

MathBio seminar: "Controlling the rate of false discoveries in tandem mass spectrum identifications"
November 14, 2016  4:00 pm  5:00 pm
318 Carolyn Lynch Laboratory
Uri Keich, University of Sydney
A typical shotgun proteomics experiment produces thousands of tandem mass spectra, each of which can be tentatively assigned a corresponding peptide by using a database search procedure that looks for a peptidespectrum match (PSM) that optimizes the score assigned to a matched pair. Some of the resulting PSMs will be correct while others will be false, and we have no way to verify which is which. The statistical problem we face is of controlling the false discovery rate (FDR), or the expected proportion of false PSMs among all reported pairings.

High Energy Seminar: "Shaving off Black Hole Soft Hair"
November 14, 2016  2:00 pm
David Rittenhouse Laboratory, 2N36
Massimo Porrati (New York University)
After recalling a definition of a black hole "hair" we explain why the only interesting hairs are those that are also remnants. Next, we will examine a recent proposal by Hawking, Perry and Strominger, who suggest that soft photons and soft gravitons can be regarded as black hole hairs that may be relevant to the black hole information paradox.

Condensed Matter seminar: "Putting Patterns on Spheres: Pollen Grains and Cholesteric Liquid Crystal Shells"
November 9, 2016  4:00 pm  5:00 pm
David Rittenhouse Laboratory, A4
Max Lavrentovich, University of Pennsylvania
Insect egg shells, mite carapaces, pollen grain surfaces, and many other biological materials exhibit intricate surface patterns including stripes, spikes, pores, and ridges.

MathBio seminar: "Changes in local chromatin structure during homology search: effects of local contacts on search time"
November 7, 2016  4:00 pm  5:00 pm
318 Carolyn Lynch Laboratory
Assaf Amitai, M.I.T.
Doublestrand break (DSB) repair by homologous recombination (HR) requires an efficient and timely search for a homologous template. We developed a statistical method of analysis based on singleparticle trajectory data which allows us to extract forces acting on chromatin at DSBs. We can differentiate between extrinsic forces from the actin cytoskeleton and intrinsic alterations on the nucleosomal level at the cleaved MAT locus in budding yeast.

High Energy Seminar: "TDuality and Scattering of Stringy States"
November 3, 2016  2:00 pm
David Rittenhouse Laboratory, 2N36
Jnan Maharana (IOP Bhubaneswar)
I shall review some of the salient features of Tduality from the
perspective of the worldsheet description of a closed compactified bosonic
string. The vertex operators associated with the moduli G and B (arising
from the compatification of graviton and antisymmetric tensor in higher
dimensions) will be constructed. The KLT formalism will be utilized to
show the Tduality transformation properties of vertex operators. 
Condensed Matter seminar: "Tracking Photoinitiated Dynamics of Photosystem I and Model Systems Through Ultrafast Spectroscopy"
November 2, 2016  4:00 pm  5:00 pm
David Rittenhouse Laboratory, A4
Jessica Anna, University of Pennsylvania
Photosystem I (PSI) is a natural light harvesting complex that catalyzes oxygenic photosynthesis through a transmembrane electron transfer. It is also known to be one of nature’s most efficient energy converters – having a quantum efficiency of 100%. The high quantum efficiency of PSI has led to many studies focusing on understanding the mechanism of electronic energy transfer and charge separation in this system.

Astro Seminar: "The Remarkable Protoplanetary Disks HL Tau: Watching the Formation of Planets"
November 2, 2016  2:00 pm  3:00 pm
David Rittenhouse Laboratory, A4
Crystal Brogan (NRAO)
Spatially resolved ALMA studies of protoplanetary disks at millimeter wavelengths are revolutionizing the study of these precursors to solar systems. In this talk I will present results from observations of the protoplanetary disk HL Tau with 3.5 AU resolution. I will also review the diverse range of modeling work that has emerged to explain the remarkable dust ring structure of HL Tau. Finally, I will show tantalizing new observational results that suggest such structures may be ubiquitous.

Experimental Particle Physics: "DiHiggs at the LHC: Current Status and Future Prospects"
November 1, 2016  1:30 pm
David Rittenhouse Laboratory, 4C8
John Alison (University of Chicago)
I will discuss motivations for searching for diHiggs production at the LHC. Recent results and projected sensitivities will be presented with particular emphasis on the dominant hh>4b channel.

MathBio seminar: "Vector diffusion maps and the graph connection Laplacian"
October 31, 2016  4:00 pm  5:00 pm
Carolyn Lynch Laboratory, 318
Amit Singer, Princeton University
Vector diffusion maps (VDM) is a mathematical framework for organizing and analyzing highdimensional datasets that generalizes diffusion maps and other nonlinear dimensionality reduction methods, such as LLE, ISOMAP, and Laplacian eigenmaps. Whereas weighted undirected graphs are commonly used to describe networks and relationships between data objects, in VDM each edge is endowed with an orthogonal transformation encoding the relationship between the data at its vertices. The graph structure and orthogonal transformations are summarized by the graph connection Laplacian.

High Energy Theory: Relative Entropy of Excited States in Conformal Field Theories
October 31, 2016  11:14 am
David RittenhouseLaboratory, 2N36
Gabor Sarosi (VUB)
We study the relative entropy between the reduced density matrices obtained from globally excited states in conformal field theories of arbitrary dimensions. We find a general formula in the small subsystem size limit. When one of the states is the vacuum of the CFT, our result matches with the holographic entanglement entropy computations in the corresponding bulk geometries, including AdS black branes. We also discuss the first asymmetric part of the relative entropy and comment on some implications of the results on the distinguishability of black hole microstates in AdS/CFT.