Talks

Quantum key distribution (QKD) is an application of quantum theory as its security relies on quantum foundations, at the same time there is development in the information-theoretic point of view to quantum theory. The security is related to impossible quantum performance, for instance, neither perfect quantum cloning nor perfect quantum state discrimination are possible. In this talk, I would like to discuss issues relevant to practical and fundamental sides of QKD: i) toward characterization of quantum correlations from which a secret key can be distilled, ii) determination whether quantum states shared by two honest parties in distance are entangled or separable, and iii) limitations on quantum performance by fundamental principles in quantum theory.

Gamma-ray production by dark matter annihilation is one of the most universal indirect dark matter signals. In order to avoid intensive astrophysical background, one can study the gamma-rays away from the Galactic plane. The problems is that the dark matter annihilation signal at high latitudes is smooth and most probably subdominant to Galactic and extragalactic fluxes. I will discuss the use of spherical harmonics decomposition as a tool to distinguish a large scale small amplitude dark matter signal from astrophysical fluxes. The sensitivity of this method for currently available Fermi data is similar to the signal from thermal WIMP dark matter annihilation into W+W- or b-bbar.

Recently rediscovered results in the theory of partial differential equations show that for free fields, the properties of the field in an arbitrarily small volume of space, traced through eternity, determine completely the field everywhere at all times. Over finite times, the field is determined in the entire region spanned by the intersection of the future null cone of the earliest event and the past null cone of the latest event. Thus this paradigm of classical field theory exhibits a fascinating form of nonlocality. I'll discuss this result and what it tells us about the possibility of constructing a classical, nonlocal theory which accommodates all the phenomena we observe.

The long awaited discovery of the double radio pulsar system, PSR J0737-3039A/B, surpassed most expectations, both theoretical and observational, as a tool to probe general relativity, stellar evolution and pulsar theories. The Double Pulsar provides a unique and the most complete and clean test of theories of gravity in a regime sensitive to possible strong-gravitational self-field effects. All six post-Keplerian parameters have been measured (including the measurement of the relativistic spin precession), some parameters to a precision of 10^{-4}.

The resonant tunneling phenomenon is well understood in quantum mechanics. I argue why a similar phenomenon must be present in quantum field theory. Using the functional Schr\"odinger method I show how resonant tunneling through multiple barriers takes place in quantum field theory with a single scalar field. I also show how this phenomenon in scalar quantum field theory can lead to an exponential enhancement of the single-barrier tunneling rate. My analysis is carried out in the thin-wall approximation. I discuss a possible explanation of the fast nucleation of the B phase of superfluid Helium-3 as an application.

While understanding the evolution of galaxies is one of the major themes of contemporary astronomy, most empirical studies focus only on the evolution of distribution functions (e.g., the luminosity function), effectively treating galaxies in isolation. The new generation of large imaging and spectroscopic surveys make it possible to measure the clustering of galaxies with different physical properties as a function of redshift, providing complementary information to traditional distribution function studies. This approach is especially powerful, because most theoretical models of galaxy evolution are based on the underlying distribution of dark matter halos and they make strong predictions for clustering evolution. To link galaxies to dark matter halos from the observed galaxy clustering, I will introduce the halo occupation distribution (HOD), which characterizes the relation between galaxies and dark matter halos by the probability distribution that a halo of virial mass M contains N galaxies of a given type, together with the spatial and velocity distributions of galaxies within halos. I will present HOD modeling results for galaxy clustering measured in several surveys, including the SDSS (z~0), the DEEP2 (z~1), and the NOAO Deep Wide-Field Surveys (0<z<1). I will demonstrate that, by linking galaxies to dark matter halos, HOD modeling of galaxy clustering opens a new direction in studying galaxy evolution (and cosmology).