| Date & time | Speaker & affiliation | Talk title & abstract |
| Apr 18 4:00pm | Mehran Kardar | The elusiveness of polymer knots
Abstract: Knots are a topological property of closed
curves, and while not rigorously defined, are also expected to occur in
sufficiently long open polymers. We argue, however, that energetic and
entropic factors favor tight knots, with the entanglements localized on
relatively small segments. Knots are also statistically rare in swollen (coil)
polymers, but abundant in compact (globular) configurations. Yet, our
investigation of the Protein Data Bank reveals very few knotted structures in
globular proteins. We shall discuss some particularly intriguing examples of
this set, including the most complicated protein knot appearing in Human
ubiquitin hydrolase.
|
| Apr 25 4:00pm | Asle Sudbø | Superconductivity in metallic hydrogen
Abstract: TBA
|
| Apr 27 Friday 4:00pm Note the unusual day |
Pinaki Sengupta (LANL) | Field Induced Supersolid Phase in Spin-One Heisenberg Models
Abstract:
We use quantum Monte Carlo methods to demonstrate that the
phase diagram of S=1 Heisenberg models with uniaxial anisotropy
contains
an extended supersolid phase. We show that this Hamiltonian is a
particular case of a more general and ubiquitous model that describes the
low energy spectrum of a class of isotropic and frustrated
spin--dimer systems. This result is crucial for finding a spin supersolid
state in real magnets. |
| May 23 4:00pm | Joost Slingerland (UCR) | Non-Abelian anyons
Abstract: TBA
|
| Jun 6 4:00pm | Armen Kocharian (CSU LA) | Electron pairings and inhomogeneous phase separation in ensemble of
nanoclusters.
Abstract: The new finer accuracy experimental and theoretical tools can unravel
local atomic scale electronic correlations in cuprates and other
transition metal oxides, which exhibit new properties that challenge
our current understanding of electronic phenomena in clusters,
nanoparticles nanomaterials, and eventually, solids. Exact
diagonalization in clusters provide a unique opportunity to get
insight into the new quantum phases and fundamental physical
properties by tuning the local inter and intra atomic parameters. I
will present the exact quantum statistical calculations of
thermodynamic phase diagrams in small Hubbard nanoclusters of various
topologies. These exact thermal studies in canonical and grand
canonical ensembles elucidate the origin microscopic charge spin
separation, electron charge and spin pairings and spin pseudogap under
doping and magnetic field. We show how in the microscopic level the
nascent charge pairing occurs and persists above Tc in the pseudogap
region, consistent with observation of incoherent pairing above Tc in
scanning tunneling microscopy (STM) measurements. The negative charge
energy gap and electron pairing give strong evidence for existence of
inhomogeneous phase separation in planar and three dimensional
clusters. The calculated phase diagrams illustrate a number of
inhomogeneous and charge ordered phases discovered in fullerene
molecules, nanoparticles, composite nanomaterials, organic conductors,
skutterudites and high Tc cuprates.
|
| Jun 13 4:00pm | Finals week |
Seminars for Fall 2005
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