20 research outputs found
Interacting Preformed Cooper Pairs in Resonant Fermi Gases
We consider the normal phase of a strongly interacting Fermi gas, which can
have either an equal or an unequal number of atoms in its two accessible spin
states. Due to the unitarity-limited attractive interaction between particles
with different spin, noncondensed Cooper pairs are formed. The starting point
in treating preformed pairs is the Nozi\`{e}res-Schmitt-Rink (NSR) theory,
which approximates the pairs as being noninteracting. Here, we consider the
effects of the interactions between the Cooper pairs in a Wilsonian
renormalization-group scheme. Starting from the exact bosonic action for the
pairs, we calculate the Cooper-pair self-energy by combining the NSR formalism
with the Wilsonian approach. We compare our findings with the recent
experiments by Harikoshi {\it et al.} [Science {\bf 327}, 442 (2010)] and
Nascimb\`{e}ne {\it et al.} [Nature {\bf 463}, 1057 (2010)], and find very good
agreement. We also make predictions for the population-imbalanced case, that
can be tested in experiments.Comment: 10 pages, 6 figures, accepted version for PRA, discussion of the
imbalanced Fermi gas added, new figure and references adde
M2-Branes and Fano 3-folds
A class of supersymmetric gauge theories arising from M2-branes probing
Calabi-Yau 4-folds which are cones over smooth toric Fano 3-folds is
investigated. For each model, the toric data of the mesonic moduli space is
derived using the forward algorithm. The generators of the mesonic moduli space
are determined using Hilbert series. The spectrum of scaling dimensions for
chiral operators is computed.Comment: 128 pages, 39 figures, 42 table
Matter and singularities
We analyze the structure of matter representations arising from codimension
two singularities in F-theory, focusing on gauge groups SU(N). We give a
detailed local description of the geometry associated with several types of
singularities and the associated matter representations. We also construct
global F-theory models for 6D and 4D theories containing these matter
representations. The codimension two singularities encountered include examples
where the apparent Kodaira singularity type does not need to be completely
resolved to produce a smooth Calabi-Yau, examples with rank enhancement by more
than one, and examples where the 7-brane configuration is singular. We identify
novel phase transitions, in some of which the gauge group remains fixed but the
singularity type and associated matter content change along a continuous family
of theories. Global analysis of 6D theories on P^2 with 7-branes wrapped on
curves of small degree reproduces the range of 6D supergravity theories
identified through anomaly cancellation and other consistency conditions.
Analogous 4D models are constructed through global F-theory compactifications
on P^3, and have a similar pattern of SU(N) matter content. This leads to a
constraint on the matter content of a limited class of 4D supergravity theories
containing SU(N) as a local factor of the gauge group.Comment: 55 pages, 7 figures; v2: references added; v3: minor correctio