Properties of Unitary Fermi Gas from the Epsilon Expansion
An analytical technique similar to the Epsilon expansion
in the theory of critical phenomena has been recently proposed for
dilute Fermi gas with two body interaction characterized by infinite scattering length and
zero effective range called Unitary Fermi Gas (Nishida and Son,
Phys.Rev.Lett.97:050403, 2006). After an introduction of the technique,
I will describe some recent results: 1. effective Lagrangian
(Landau-Ginzburg functional) for Unitary Fermi Gas and its applications
(superfluid vortex structure, surface tension of the normal/superfluid
phase interface in the polarized (imbalanced) gas, etc); 2. low energy
density-density correlation function and the dynamic structure factor.
| Date | Speaker (link to SPIRES) |
Title (abstract) |
| 26th Sep 2007 (Wed) |
Assumpta Parreño (U. Barcelona, Cataluña) |
Extracting Low-Energy Hadron
Physics from Lattice QCD (.pdf-file) Lattice QCD simulations of the hadron-hadron interactions can be very useful in situations where experimental guidance to phenomenological calculations is missing. Moreover, they can determine how nuclear processes depend upon fundamental constants of nature. Within this framework, I will discuss recent efforts carried out by the Nuclear Physics Lattice QCD Collaboration, and present some results for the low-energy scattering parameters in the nonstrange and strange baryon-baryon and meson-meson sectors. These simulations have been performed with domain-wall valence quarks on dynamical staggered gauge configurations with lattice spacing of $b=0.125~{\rm fm}$ and pion masses between $m_\pi \approx 300 - 500$ MeV. We will consider the possibility of a first principles calculation of nuclear forces from QCD and discuss the practical and conceptual issues arising. The first (and most recent) numerical results will shown. See also hep-lat/0602010 (nucleon-nucleon), hep-lat/0612026 (hyperon-nucleon). |
| 4th Oct 2007 (Thu) | Brian
C. Tiburzi
(U. of Maryland at College Park) |
Polarizabilities in Lattice QCD (.pdf-file) Hadronic polarizabilities have been the focus of dedicated work, both experimentally and theoretically, for decades. I describe calculations of polarizabilities both from the lattice perspective, and from chiral perturbation theory. I argue that the two approaches in conjunction will help us test our understanding of chiral physics, and maybe even understand experimental data. See also arXiv:0709.1955 [hep-lat], hep-lat/0610018, hep-lat/0603026. |
| 11th
Oct 2007 (Thu) |
No Seminar (DNP meeting) |
|
| 18th Oct 2007 (Thu) |
No Seminar (SCALE-UP presentation) | |
| 25th Oct 2007 (Thu) | No Seminar | |
| 1st Nov 2007 (Thu) | Andrei Alexandru (GWU) |
Simulating QCD at non-zero baryon
density I will review the status of lattice simulations at finite temperature and zero baryon density and then discuss the challenges that we face when trying to simulate QCD at non-zero baryon density. I will briefly present the status of lattice QCD simulations in this area, the problems that need to be solved and what is new in the approach we are using. |
| 8th Nov 2007 (Thu) | Andrea Pocar (Stanford U.) * |
Borexino: First
Real-Time Detection of Sub-MeV Solar Neutrinos (.pdf-file) Borexino is an ultra-low background experiment for spectroscopy of low-energy neutrinos. The primary physics goal is the real time detection of the 7Be, pep and CNO solar neutrinos fluxes with energies below 2 MeV. Borexino is aiming at observing anti-neutrinos from the Earth’s crust. A fundamental problem in the observation of sub-MeV neutrinos is that of the traces of radioactive isotopes present intrinsically in nearly all materials. Borexino is a pioneer in achieving unprecedented low levels of radioactive impurities. Strategies to combat radioactivity include (but are not limited to) the principle of graded shielding, materials screening, clean room assembly, radon filtering, use of purification plants, and discrimination between the scintillation pulse shapes of alpha particle and electron-induced events. Armed with these tools, Borexino has recently made the first observation of the 862-keV neutrinos formed in the 7Be side branch of the pp solar fusion cycle, which represent about 10% of solar neutrino output. This talk will discuss some experimental details that have permitted us to meet this goal, and will put the Borexino result within the framework of current models of neutrino and solar physics. |
| 15th Nov 2007 (Thu) | Ivan Horvath (U of Kentucky) |
Topological Structure of the QCD Vacuum Deciphering the vacuum structure of QCD is one of the unsolved mysteries in particle physics. This is not just an academic intellectual challenge. Rather, it is expected that the true understanding will offer new quantitative handles on strong-interaction physics. We will describe how lattice QCD can be systematically used toward achieving this goal. Particular emphasis will be put on the topological aspects of the vacuum where qualitatively new results were recently obtained. Unexpected new insight in this area will be discussed in detail. |
| 22nd Nov 2007 (Thu) | No Seminar (Turkey Day) | |
| 29th
Nov 2007 (Thu) |
Tanja Horn (Jefferson Lab.) |
Scaling Study of the Pion
Electroproduction Cross Sections and the Pion From Factor (.pdf-file) One of the main objectives of Jefferson Lab is to understand the structure of the nucleon in terms of the quark-gluon degrees of freedom. Measurements of inclusive processes, like deep inelastic scattering (DIS), have shown that in the limit of large Q^2, at fixed values of x_B, such processes can be viewed as scattering from individual partons within the hadronic system. A similar factorization of scales, allowing perturbative QCD concepts to be used in the description of hadrons, may be expected in hard exclusive processes. The Q^2 dependence of the separated p(e,e' pi+)n cross sections provides one of the best ways to test the factorization of long-distance from short-distance physics, and at which values of Q^2 it applies. Such tests will lay the foundation for a reliable interpretation of the results from the GPD program at Jefferson Lab, and for GPD studies with a future electron-ion collider. In this talk I will present a QCD scaling study using published H(e,e'pi+)n cross sections and pion form factor results. The extension of these studies to higher Q^2 by future experiments at Jefferson Lab, accepted to run after the 12 GeV upgrade will also be discussed. |
| 3rd Dec 2007 (Mon) Cor 104 Special Date & Time |
Lei Guo (Jefferson Lab.) | QCD Spectroscopy, Structure and Dynamics: Opportunities at JLab (.pdf-file) Hadron spectroscopy remains one of the essential experimental means of probing quark confinement and other fundamental properties of QCD. Jefferson Lab is one of the leading centers of both experimental and theoretical efforts in hadron physics. Recent experimental efforts that I have been involved with, mainly from CLAS: exotic meson search, hyperon physics, and cascade spectroscopy will be presented. The intimate relationship between various aspects of hadron spectroscopy will be discussed. Future experiments that aim for further investigation of these issues, both at hall B and D, will also be addressed. |
| 6th
Dec 2007 (Thu) |
Andrei
Kryjevski (Washington U., St. Louis) * |
Properties of Unitary Fermi Gas from the Epsilon Expansion An analytical technique similar to the Epsilon expansion in the theory of critical phenomena has been recently proposed for dilute Fermi gas with two body interaction characterized by infinite scattering length and zero effective range called Unitary Fermi Gas (Nishida and Son, Phys.Rev.Lett.97:050403, 2006). After an introduction of the technique, I will describe some recent results: 1. effective Lagrangian (Landau-Ginzburg functional) for Unitary Fermi Gas and its applications (superfluid vortex structure, surface tension of the normal/superfluid phase interface in the polarized (imbalanced) gas, etc); 2. low energy density-density correlation function and the dynamic structure factor. |
Back to Center
for Nuclear Studies Home Page, Department of Physics
Home Page.
Harald W. Griesshammer,
Autumn 2007