Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Primordial Black Hole Evaporation and Spontaneous Dimensional Reduction   Several different approaches to quantum gravity suggest the effective
dimension of spacetime reduces from four to two near the Planck scale. In light
of such evidence, this letter re-examines the thermodynamics of primordial
black holes (PBHs) in specific lower-dimensional gravitational models. Unlike
in four dimensions, $\done$-D black holes radiate with power $P \sim \Mbh^2$,
while it is known no $(2+1)-$D (BTZ) black holes can exist in a
non-anti-deSitter universe. This has important relevance to the PBH population
size and distribution, and consequently on cosmological evolution scenarios.
The number of PBHs that have evaporated to present day is estimated, assuming
they account for all dark matter. Entropy conservation during dimensional
transition imposes additional constraints. If the cosmological constant is
non-negative, no black holes can exist in the $(2+1)$-dimensional epoch, and
consequently a $(1+1)$-dimensional black hole will evolve to become a new type
of remnant. Although these results are conjectural and likely model-dependent,
they open new questions about the viability of PBHs as dark matter candidates.

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The categories of this paper are: cond-mat
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The categories of this paper are: q-fin
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The categories of this paper are: nucl-ex
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The categories of this paper are: dg-ga
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The categories of this paper are: hep-ph
27
The categories of this paper are: comp-gas
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The categories of this paper are: chao-dyn
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The categories of this paper are: funct-an
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The categories of this paper are: acc-phys
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The categories of this paper are: q-bio
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The categories of this paper are: alg-geom
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The categories of this paper are: q-alg
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The categories of this paper are: nucl-th
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The categories of this paper are: bayes-an
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The categories of this paper are: math
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The categories of this paper are: eess