Scientific Series

F-theory based vacua provide a potentially promising starting point for realizing Grand Unified Theories (GUTs) in string theory. In minimal realizations of this framework based on a point of E8 unification, this turns out to be quite constraining, and leads to specific expectations for the form of supersymmetry breaking. We discuss how the parameters of the F-theory GUT determine the sparticle spectrum, and possible signatures at the LHC.

We show that when a volume of quark matter rotates, there is an axial current flowing along the rotation axis. This effect has been overlooked in all previous treatments of relativistic fluids until calculations using gauge/gravity duality indicate it existence. The effect is a manifestation of triangle anomalies, and may exhibit itself in heavy ion collisions with nonzero impact parameter.

Binary neutron stars are among the most important sources of gravitational waves which are expected to be detected by the current or next generation of gravitational wave detectors, such as LIGO and Virgo, and they are also thought to be at the origin of very important astrophysical phenomena, such as short gamma-ray bursts. In order to describe the dynamics of these events one needs to solve the full set of general relativistic magnetohydrodynamics equations through the use of parallel numerical codes. I will report on some recent results obtained with the use of the fully general relativistic magnetohydrodynamic code Whisky in simulating binary neutron stars which inspiral and merge forming an hypermassive neutron star which eventually collapses to form a black hole surrounded by a torus. I will in particular describe how mass, equation of state and magnetic fields can affect the dynamics and consequently the gravitational waves emitted by these systems and discuss about their possible connection with the formation of short gamma ray bursts.

"Extended" topological field theory generalizes ordinary TQFT to include spacetimes with boundary. Starting from a gauge theory of flat G-connections, and its boundary restriction, I will describe a plan for constructing an extended topological field theory, for any compact Lie group G. This is based on work-in-progress with Jeffrey Morton.

Viscosity is a very old concept which was introduced to physics by Navier in the 19th century. However, in strongly coupled systems, the viscosity is usually difficult to compute. In this talk I will describe how gauge/gravity duality, a by-product of string theory, allows one to compute the viscosity for a class of strongly interacting fluids not too dissimilar to the quark gluon plasma. I will also describe efforts to measure the viscosity and other physical properties of the quark gluon plasma at the Relativistic Heavy Ion Collider.

We will review the definitions of spin foam models for quantum gravity and the recent advances in this field, such as the "graviton propagator", the definition of coherent states of geometry and the derivation of non-commutative field theories as describing the effective dynamics of matter coupled to quantum gravity. I will insist on the role of group field theories as providing a non-perturbative definition of spinfoams and their intricate relation with non-commutative geometry and matrix models.

It has recently uncovered that the intertwiner space for LQG carries a natural representation of the U(N) unitary group. I will describe this U(N) action in details and show how it can be used to compute the LQG black hole entropy, to define coherent intertwiner states and to reformulate the LQG dynamics in new terms.

We describe a class of non-Fermi liquid systems, using the AdS/CFT correspondence. The Fermi surfaces are studied by computing the response functions of fermionic operators. The scaling behavior near the Fermi surfaces is determined by conformal dimensions in an emergent IR CFT. The low-energy excitations near the Fermi momenta are not Landau quasiparticles. When the operator is marginal in the IR CFT, the full spectral function is precisely of the `marginal Fermi liquid' form, introduced as a phenomenological model of the `strange metal' phase of high temperature superconductors.

The sneutrino is a viable NLSP candidate in SUSY with gravitino LSP. In my talk I will focus on this possibility, in particular concentrating on the question of whether the LHC can distinguish spectra with a sneutrino NLSP from alternatives, e.g. ones with neutralino LSP. I will show that there are at least two different families of experimentally allowed spectra with sneutrino NLSP which exhibit distinctive multilepton signals. These spectra are not easy to fake within the MSSM. I will discuss these signals in detail and illustrate our analysis approach on simulations.

Last May, NASA astronauts performed a challenging and flawless Space Shuttle servicing mission to the orbiting Hubble Space Telescope. With science instruments repaired on board and incredible new ones installed, the observatory is more powerful now than ever before. I will show the dramatic highlights of the mission, and present some of the first results from the refurbished telescope. The sensitivity and multi-wavelength capabilities are revealing the highest redshift galaxies ever seen as well as details of the cosmic web of intergalactic medium, large scale structure formation, and stellar evolution. Studies of dark matter, dark energy, and exoplanet atmospheres add to the profound contributions to astrophysics that Hubble is making, at the new apex of its capabilities.

In quantum information, entanglement has often been viewed as a resource. But in this talk, I will look at (pure bipartite) entanglement through the lens of superselection rules. The idea is that it requires quantum communication not only to create entanglement, but also to destroy it in a way that doesn't leak information to the environment. As a result, when communication is scarce, superpositions of different numbers of EPR pairs can be difficult to obtain. This constraint is not a strict superselection rule, but rather an approximate version that gives rigorous bounds on achievable fidelities. After describing the general phenomenon, I will show how it relates to communication complexity, information theory and fairy tales about princesses. This talk is based on 0803.3066, 0909.1557, 0912.5537 and other unpublished work.