Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Studies on the SJ Vacuum in de Sitter Spacetime   In this work we study the Sorkin-Johnston (SJ) vacuum in de Sitter spacetime
for free scalar field theory. For the massless theory we find that the SJ
vacuum can neither be obtained from the $O(4)$ Fock vacuum of Allen and Folacci
nor from the non-Fock de Sitter invariant vacuum of Kirsten and Garriga. Using
a causal set discretisation of a slab of 2d and 4d de Sitter spacetime, we find
the causal set SJ vacuum for a range of masses $m \geq 0$ of the free scalar
field. While our simulations are limited to a finite volume slab of global de
Sitter spacetime, they show good convergence as the volume is increased. We
find that the 4d causal set SJ vacuum shows a significant departure from the
continuum Motolla-Allen $\alpha$-vacua. Moreover, the causal set SJ vacuum is
well-defined for both the minimally coupled massless $m=0$ and the conformally
coupled massless $m=m_c$ cases. This is at odds with earlier work on the
continuum de Sitter SJ vacuum where it was argued that the continuum SJ vacuum
is ill-defined for these masses. Our results hint at an important tension
between the discrete and continuum behaviour of the SJ vacuum in de Sitter and
suggest that the former cannot in general be identified with the Mottola-Allen
$\alpha$-vacua even for $m>0$.

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The categories of this paper are: patt-sol
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The categories of this paper are: q-fin
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The categories of this paper are: chem-ph
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The categories of this paper are: q-alg
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The categories of this paper are: acc-phys
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The categories of this paper are: funct-an
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The categories of this paper are: quant-ph
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The categories of this paper are: hep-lat
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The categories of this paper are: cmp-lg
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The categories of this paper are: solv-int
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The categories of this paper are: physics
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The categories of this paper are: supr-con
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The categories of this paper are: nlin
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The categories of this paper are: cond-mat
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The categories of this paper are: math-ph
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The categories of this paper are: nucl-th