# Metrics on End-Periodic Manifolds as Models for Dark Matter

By: Christopher L Duston

In this paper we will detail an approach to generate metrics and matter
models on end-periodic manifolds, which are used extensively in the study of
the exotic smooth structures of $\mathbb{R}^4$. We will present three distinct
examples, discuss their associated matter models by solving the Einstein
equations, and determine their physical viability by examining the energy
conditions. We will also compare one of the models directly with exis... more

In this paper we will detail an approach to generate metrics and matter
models on end-periodic manifolds, which are used extensively in the study of
the exotic smooth structures of $\mathbb{R}^4$. We will present three distinct
examples, discuss their associated matter models by solving the Einstein
equations, and determine their physical viability by examining the energy
conditions. We will also compare one of the models directly with existing
models of matter distributions in extragalactic systems, to highlight the
viability of utilizing exotic smooth structures to understand the existence and
distribution of dark matter.
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# Exotic Smoothness in Four Dimensions and Euclidean Quantum Gravity

By: Christopher L Duston

In this paper we calculate the effect of the inclusion of exotic smooth
structures on typical observables in Euclidean quantum gravity. We do this in
the semiclassical regime for several gravitational free-field actions and find
that the results are similar, independent of the particular action that is
chosen. These are the first results of their kind in dimension four, which we
extend to include one-loop contributions as well. We find thes... more

In this paper we calculate the effect of the inclusion of exotic smooth
structures on typical observables in Euclidean quantum gravity. We do this in
the semiclassical regime for several gravitational free-field actions and find
that the results are similar, independent of the particular action that is
chosen. These are the first results of their kind in dimension four, which we
extend to include one-loop contributions as well. We find these topological
features can have physically significant results without the need for
additional exotic physics.
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# Back to the Future: Causality on a Moving Braneworld

By: Brian Greene, Daniel Kabat, Janna Levin, Massimo Porrati

Brane observers executing appropriate motion through a partially compactified Lorentz invariant bulk spacetime, such as M4xS1, can send signals along the brane that are instantaneous or even travel backward in time. Nevertheless, causality in the braneworld remains intact. We establish these results, which follow from superluminal signal propagation reported in arXiv:2206.13590, through classical analysis and then extend our reasoning by ex... more

Brane observers executing appropriate motion through a partially compactified Lorentz invariant bulk spacetime, such as M4xS1, can send signals along the brane that are instantaneous or even travel backward in time. Nevertheless, causality in the braneworld remains intact. We establish these results, which follow from superluminal signal propagation reported in arXiv:2206.13590, through classical analysis and then extend our reasoning by examining quantum mechanical microcausality. One implication is the capacity
for real time communication across arbitrarily large distances.
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