Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Underdoped cuprates, manifestations of boson-fermion crossover, `quantum
  oscillations' and the robust fractional quantum Hall state nu = 2/5   The quantum oscillation data from a whole variety of underdoped HTSC systems
and physical measurements has almost universally been presented in very
classical terms following the Lifshitz-Kosevich formulation for Fermi-Landau
quasiparticles, quantized into vortices and Landau levels under the high
applied magnetic fields. The Fermi surface always emerges as a very small
fraction of the large parent Fermi surface detected at higher doping. This then
calls for some Fermi surface reconstruction to have occurred, as from a charged
density wave, etc.. The paper refutes this reciprocal space approach, and shows
that many of the more recent detailed works taking this line are not consistent
with the data. The present author developed an alternative real-space
interpretation of these matters a couple of years ago. This was in terms of
interaction of the vortex array with the stripe array, using a 2D modelling for
the latter. This approach has here been revised slightly and copes well with
addressing the wide variety of new data. The paper pursues and justifies the
BEC/BCS, negative-U based, two-subsystem modelling advocated earlier, along
with the strength and geometry of the striping acquired in a strong magnetic
field. A wide variety of recent experiments are expounded to produce an overall
appreciation of a situation far from being appropriately treated within a
Fermi-Landau quasiparticle framework. Indeed it is demonstrated that the
universality of the 'QO' observations ensues from the fractional quantum Hall
effect. The data all point to FQHE state with filling factor nu = 2/5. This
state in its genesis and expression finds a much greater alignment with the
BEC/BCS crossover condition and the proximity of the HTSC materials to
Mott-Anderson localization than does any model for this highly correlated
material appealing to well-metallized Fermi-Landau quasiparticle physics.

37
The categories of this paper are: supr-con
2
The categories of this paper are: math
32
The categories of this paper are: atom-ph
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The categories of this paper are: mtrl-th
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The categories of this paper are: patt-sol
16
The categories of this paper are: stat
24
The categories of this paper are: dg-ga
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The categories of this paper are: solv-int
7
The categories of this paper are: hep-th
36
The categories of this paper are: cmp-lg
11
The categories of this paper are: hep-lat
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The categories of this paper are: adap-org
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The categories of this paper are: eess
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The categories of this paper are: alg-geom
10
The categories of this paper are: q-bio
8
The categories of this paper are: hep-ex