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We discuss models in which vacua other than our own can be directly observed in the present universe. Models with density-dependent vacuum structure can give rise to `non-lethal-vacua: vacua with lower energy-density than our vacuum, but only in regions with finite Standard Model densities. These models provide an explicit example of a bubble which is confined to a finite region of space and produces potentially detectable signatures, unlike standard Coleman tunneling events where bubbles expand at the speed of light and are never directly observable. We study the expansion and contraction of a confined bubble created after a core-collapse supernova, focusing on energy deposition that may be observable in the vicinity of a supernova remnant due to the formation and evolution of a confined bubble.
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The detection of an oscillating pattern in the bispectrum of density perturbations could suggest the existence of a high-energy second minimum in the Higgs potential. If the Higgs field resided in this new minimum during inflation and was brought back to the electroweak vacuum by thermal corrections during reheating, the coupling of Standard Model particles to the inflaton would leave its imprint on the bispectrum. We focus on the fermions, whose dispersion relation can be modified by the coupling to the inflaton, leading to an enhanced particle production during inflation even if their mass during inflation is larger than the Hubble scale. This results in a large non-analytic contribution to non-Gaussianities, with an amplitude $f_{rm NL}$ as large as $100$ in the squeezed limit, potentially detectable in future 21-cm surveys. Measuring the contributions from two fermions would allow us to compute the ratio of their masses, and to ascribe the origin of the signal to a new Higgs minimum. Such a discovery would be a tremendous step towards understanding the vacuum instability of the Higgs potential, and could have fascinating implications for anthropic considerations.
According to General Relativity (GR) a universe with a cosmological constant, Lambda, like ours, is trapped inside an event horizon r< sqrt(3/Lambda). What is outside? We show, using Israel (1967) junction conditions, that there could be a different universe outside. Our Universe looks like a Black Hole for an outside observer. Outgoing radial null geodesics can not escape our universe, but incoming photons can enter and leave an imprint on our CMB sky. We present a picture of such a fossil record from the analysis of CMB maps that agrees with the Black Hole universe predictions but challenge our understanding of the origin of the primordial universe.
Higgsplosion is a dynamical mechanism that introduces an exponential suppression of quantum fluctuations beyond the Higgsplosion energy scale E_* and further guarantees perturbative unitarity in multi-Higgs production processes. By calculating the Higgsplosion scale for spin 0, 1/2, 1 and 2 particles at leading order, we argue that Higgsplosion regulates all n-point functions, thereby embedding the Standard Model of particle physics and its extensions into an asymptotically safe theory. There are no Landau poles and the Higgs self-coupling stays positive. Asymptotic safety is of particular interest for theories of particle physics that include quantum gravity. We argue that in a Hippsloding theory one cannot probe shorter and shorter length scales by increasing the energy of the collision beyond the Higgsplosion energy and there is a minimal length set by r_* ~ 1/E_* that can be probed. We further show that Higgsplosion in consistent and not in conflict with models of inflation and the existence of axions. There is also a possibility of testing Higgsplosion experimentally at future high energy experiments.
The search for and identification of neutralino dark matter in supersymmetry requires a multi-pronged approach with important roles played by collider, direct and indirect dark matter detection experiments. In this report, we summarize the sensitivity of such searches at the 7, 8 (and eventually 14) TeV LHC, combined with those by Fermi, CTA, IceCube/DeepCore, COUPP and XENON1T, to such particles within the context of the 19-parameter p(henomenological)MSSM. This report provides an outline of the current status of our results and our expectations for future analyses.
Motivated by string dualities we propose topological gravity as the early phase of our universe. The topological nature of this phase naturally leads to the explanation of many of the puzzles of early universe cosmology. A concrete realization of this scenario using Wittens four dimensional topological gravity is considered. This model leads to the power spectrum of CMB fluctuations which is controlled by the conformal anomaly coefficients $a,c$. In particular the strength of the fluctuation is controlled by $1/a$ and its tilt by $c g^2$ where $g$ is the coupling constant of topological gravity. The positivity of $c$, a consequence of unitarity, leads automatically to an IR tilt for the power spectrum. In contrast with standard inflationary models, this scenario predicts $mathcal{O}(1)$ non-Gaussianities for four- and higher-point correlators and the absence of tensor modes in the CMB fluctuations.
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