On the (Non)Hadamard property of the SJ state in a 1 + 1 D causal diamond

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Abstract

jats:titleAbstract</jats:title> jats:pThe Sorkin–Johnston (SJ) state is a candidate physical vacuum state for a scalar field in a generic curved spacetime. It has the attractive feature that it is covariantly and uniquely defined in any globally hyperbolic spacetime, often reflecting the underlying symmetries if there are any. A potential drawback of the SJ state is that it does not always satisfy the Hadamard condition. In this work, we study the extent to which the SJ state in a jats:inline-formula jats:tex-math</jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> mml:mn1</mml:mn> mml:mo+</mml:mo> mml:mn1</mml:mn> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cqgad1ce2ieqn2.gif" xlink:type="simple" /> </jats:inline-formula>D causal diamond is Hadamard, finding that it is not Hadamard at the boundary. We then study the softened SJ state, which is a slight modification of the original state to make it Hadamard. We use the softened SJ state to investigate whether some peculiar features of entanglement entropy in causal set theory may be linked to its non-Hadamard nature.</jats:p>

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Keywords
4902 Mathematical Physics, 49 Mathematical Sciences, 51 Physical Sciences
Journal Title
Classical and Quantum Gravity
Conference Name
Journal ISSN
0264-9381
1361-6382
Volume Title
41
Publisher
IOP Publishing