Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Zero Sound in Strange Metallic Holography   One way to model the strange metal phase of certain materials is via a
holographic description in terms of probe D-branes in a Lifshitz spacetime,
characterised by a dynamical exponent z. The background geometry is dual to a
strongly-interacting quantum critical theory while the probe D-branes are dual
to a finite density of charge carriers that can exhibit the characteristic
properties of strange metals. We compute holographically the low-frequency and
low-momentum form of the charge density and current retarded Green's functions
in these systems for massless charge carriers. The results reveal a
quasi-particle excitation when z<2, which in analogy with Landau Fermi liquids
we call zero sound. The real part of the dispersion relation depends on
momentum k linearly, while the imaginary part goes as k^2/z. When z is greater
than or equal to 2 the zero sound is not a well-defined quasi-particle. We also
compute the frequency-dependent conductivity in arbitrary spacetime dimensions.
Using that as a measure of the charge current spectral function, we find that
the zero sound appears only when the spectral function consists of a single
delta function at zero frequency.

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The categories of this paper are: chem-ph
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The categories of this paper are: funct-an
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The categories of this paper are: physics
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The categories of this paper are: nucl-th
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The categories of this paper are: cs
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The categories of this paper are: math
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The categories of this paper are: chao-dyn
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The categories of this paper are: hep-ph
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The categories of this paper are: eess
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The categories of this paper are: patt-sol
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The categories of this paper are: acc-phys
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The categories of this paper are: cmp-lg
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The categories of this paper are: stat
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The categories of this paper are: bayes-an
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The categories of this paper are: atom-ph
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The categories of this paper are: comp-gas