Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Anomalous Expansion of Attractively Interacting Fermionic Atoms in an
  Optical Lattice   Strong correlations can dramatically modify the thermodynamics of a quantum
many-particle system. Especially intriguing behaviour can appear when the
system adiabatically enters a strongly correlated regime, for the interplay
between entropy and strong interactions can lead to counterintuitive effects. A
well known example is the so-called Pomeranchuk effect, occurring when liquid
3He is adiabatically compressed towards its crystalline phase. Here, we report
on a novel anomalous, isentropic effect in a spin mixture of attractively
interacting fermionic atoms in an optical lattice. As we adiabatically increase
the attraction between the atoms we observe that the gas, instead of
contracting, anomalously expands. This expansion results from the combination
of two effects induced by pair formation in a lattice potential: the
suppression of quantum fluctuations as the attraction increases, which leads to
a dominant role of entropy, and the progressive loss of the spin degree of
freedom, which forces the gas to excite additional orbital degrees of freedom
and expand to outer regions of the trap in order to maintain the entropy. The
unexpected thermodynamics we observe reveal fundamentally distinctive features
of pairing in the fermionic Hubbard model.

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The categories of this paper are: hep-ph
32
The categories of this paper are: atom-ph
26
The categories of this paper are: bayes-an
12
The categories of this paper are: nucl-th
5
The categories of this paper are: gr-qc
19
The categories of this paper are: eess
25
The categories of this paper are: patt-sol
3
The categories of this paper are: physics
37
The categories of this paper are: supr-con
1
The categories of this paper are: cs
28
The categories of this paper are: alg-geom
31
The categories of this paper are: ao-sci
15
The categories of this paper are: nucl-ex
16
The categories of this paper are: stat
7
The categories of this paper are: hep-th
35
The categories of this paper are: mtrl-th