6 research outputs found
A Common Origin for Neutrino Anarchy and Charged Hierarchies
The generation of exponential flavor hierarchies from extra-dimensional
wavefunction overlaps is re-examined. We find, surprisingly, that coexistence
of anarchic fermion mass matrices with such hierarchies is intrinsic and
natural to this setting. The salient features of charged fermion and neutrino
masses and mixings can thereby be captured within a single framework. Both
Dirac and Majorana neutrinos can be realized. The minimal phenomenological
consequences are discussed, including the need for a fundamental scale far
above the weak scale to adequately suppress flavor-changing neutral currents.
Two broad scenarios for stabilizing this electroweak hierarchy are studied,
warped compactification and supersymmetry. In warped compactifications and
"Flavorful Supersymmetry," where non-trivial flavor structure appears in the
new TeV physics, Dirac neutrinos are strongly favored over Majorana by lepton
flavor violation tests. We argue that this is part of a more general result for
flavor-sensitive TeV-scale physics. Our scenario strongly suggests that the
supersymmetric flavor problem is not solved locally in the extra dimension, but
rather at or below the compactification scale. In the supersymmetric Dirac
case, we discuss how the appearance of light right-handed sneutrinos
considerably alters the physics of dark matter.Comment: Comparison with the Froggatt-Nielsen mechanism omitted. Some
clarifications added. This is the version accepted by PRL with a longer
abstract
An SU(N) Mott insulator of an atomic Fermi gas realized by large-spin Pomeranchuk cooling
The Hubbard model, containing only the minimum ingredients of nearest
neighbor hopping and on-site interaction for correlated electrons, has
succeeded in accounting for diverse phenomena observed in solid-state
materials. One of the interesting extensions is to enlarge its spin symmetry to
SU(N>2), which is closely related to systems with orbital degeneracy. Here we
report a successful formation of the SU(6) symmetric Mott insulator state with
an atomic Fermi gas of ytterbium (173Yb) in a three-dimensional optical
lattice. Besides the suppression of compressibility and the existence of charge
excitation gap which characterize a Mott insulating phase, we reveal an
important difference between the cases of SU(6) and SU(2) in the achievable
temperature as the consequence of different entropy carried by an isolated
spin. This is analogous to Pomeranchuk cooling in solid 3He and will be helpful
for investigating exotic quantum phases of SU(N) Hubbard system at extremely
low temperatures.Comment: 20 pages, 6 figures, to appear in Nature Physic
Content-based image retrieval based on colour histogram and the discrete cosine transform
We study the static screening in a Hubbard-like model using fixed-node
diffusion Monte Carlo. We find that the random phase approximation is
surprisingly accurate even for metallic systems close to the Mott transition.
As a specific application we discuss the implications of the efficient
screening for the superconductivity in the doped Fullerenes. In the Monte Carlo
calculations we use trial functions with two Gutzwiller-type parameters. To
deal with such trial functions, we introduce a method for efficiently
optimizing the Gutzwiller parameters, both in variational and in fixed-node
diffusion Monte Carlo.Comment: 4 pages LaTeX with 4 eps figures; Computer Simulations Studies in
Condensed Matter Physics XII, Eds.: D.P. Landau, S.P. Lewis, and H.B.
Schuettler, Springer 1999; additional material available at
http://www.mpi-stuttgart.mpg.de/docs/ANDERSEN/fullerene