Letters in High Energy Physics 2021-03-19T20:09:33+00:00 Professor Shaaban Khalil Open Journal Systems Noncommutative-Geometry Wormholes with Isotropic Pressure 2021-02-02T14:59:41+00:00 Peter K. F. Kuhfittig <p>The strategy adopted in the original Morris-Thorne wormhole was to retain complete control over the geometry at the expense of certain engineering considerations. The purpose of this paper is to obtain several complete wormhole solutions by assuming a noncommutative-geometry background with a concomitant isotropic pressure condition. This condition allows us to consider a cosmological setting with a perfect-fluid equation of state. An extended form of the equation generalizes the first solution and subsequently leads to the generalized Chaplygin gas model and hence to a third solution. The solutions obtained extend several previous results. This paper also reiterates the need for a noncommutative-geometry background to account for the enormous radial tension that is a characteristic of Morris-Thorne wormholes.</p> 2021-01-31T05:45:26+00:00 ##submission.copyrightStatement## String Theory, the Dark Sector, and the Hierarchy Problem 2021-02-08T07:09:17+00:00 Per Berglund Tristan Hubsch Djordje Minic <p>We discuss dark energy, dark matter, and the hierarchy problem in the context of a general noncommutative formulation of string theory. In this framework, dark energy is generated by the dynamical geometry of the dual spacetime while dark matter, on the other hand, comes from the degrees of freedom dual to the visible matter. This formulation of string theory is sensitive to both the IR and UV scales, and the Higgs scale is radiatively stable by being a geometric mean of radiatively stable UV and IR scales. We also comment on various phenomenological signatures of this novel approach to dark energy, dark matter, and the hierarchy problem. We find that this new view on the hierarchy problem is realized in a toy model based on a nonholomorphic deformation of the stringy cosmic string. Finally, we discuss a proposal for a new nonperturbative formulation of string theory, which sheds light on M-theory and F-theory, as well as on supersymmetry and holography.</p> 2021-01-28T00:00:00+00:00 ##submission.copyrightStatement## Comments on Brane Recombination, Finite Flux Vacua, and the Swampland 2021-02-19T17:16:11+00:00 Jason Kumar James D. Wells <p>The Swampland program relies heavily on the conjecture that there can only be a finite number of flux vacua (FFV conjecture). Stipulating this FFV conjecture and applying it to some older work in flux vacua construction, we show that within a patch of the landscape the FFV conjecture makes predictions on the nonexistence of otherwise viable nonperturbative objects arising from brane recombination. Future gains in the direct nonperturbative analysis could, therefore, not only test this prediction but also test portions of the Swampland program itself. We also discuss implications of a weaker FFV conjecture on the counting of flux vacua which predicts the positivity of the brane central charge if the EFT analysis is to be qualitatively trusted.</p> 2021-02-19T07:56:09+00:00 ##submission.copyrightStatement## de Sitter Complementarity, TCC, and the Swampland 2021-03-06T19:21:15+00:00 Alek Bedroya <p>Motivated by the coincidence of scrambling time in de Sitter and maximum lifetime given by the Trans-Planckian Censorship Conjecture (TCC), we study the relation between the de Sitter complementarity and the Swampland conditions. We study thermalization in de Sitter space from different perspectives and show that TCC implies de Sitter space cannot live long enough to be considered a thermal background. We also revisit&nbsp;\(\alpha\)-vacua in light of this work and show that TCC imposes multiple initial condition/fine-tuning problems on any conventional inflationary scenario.<br><br></p> 2021-03-05T20:53:42+00:00 ##submission.copyrightStatement## Trans-Planckian Censorship Conjecture and Early Universe Cosmology 2021-03-19T20:09:33+00:00 Robert Brandenberger <p>I review the Trans-Planckian Censorship Conjecture (TCC) and its implications for cosmology, in particular for the inflationary universe scenario. Whereas the inflationary scenario is tightly constrained by the TCC, alternative early universe scenarios are not restricted.</p> 2021-03-19T13:45:12+00:00 ##submission.copyrightStatement##