127 research outputs found

    Neutrino Zero Modes and Stability of Electroweak Strings

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    We discuss massless and massive neutrino zero modes in the background of an electroweak string. We argue that the eventual absence of the neutrino zero mode implies the existence of topologically stable strings where the required non-trivial topology has been induced by the fermionic sector.Comment: 6 pages, 2 figures, Presented at DPF 2000: The Meeting of the Division of Particles and Fields of the American Physical Society, Columbus, Ohio, 9-12 Aug 2000. Proceedings to be published in International Journal of Modern Physics

    Emergent Spacetime in Stochastically Evolving Dimensions

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    Changing the dimensionality of the space-time at the smallest and largest distances has manifold theoretical advantages. If the space is lower dimensional in the high energy regime, then there are no ultraviolet divergencies in field theories, it is possible to quantize gravity, and the theory of matter plus gravity is free of divergencies or renormalizable. If the space is higher dimensional at cosmological scales, then some cosmological problems (including the cosmological constant problem) can be attacked from a completely new perspective. In this paper, we construct an explicit model of "evolving dimensions" in which the dimensions open up as the temperature of the universe drops. We adopt the string theory framework in which the dimensions are fields that live on the string worldsheet, and add temperature dependent mass terms for them. At the Big Bang, all the dimensions are very heavy and are not excited. As the universe cools down, dimensions open up one by one. Thus, the dimensionality of the space we live in depends on the energy or temperature that we are probing. In particular, we provide a kinematic Brandenberger-Vafa argument for how a discrete {\it causal set}, and eventually a continuum (3+1)(3+1)-dim spacetime along with Einstein gravity emerge in the Infrared from the worldsheet action. The (3+1)(3+1)-dim Planck mass and the string scale become directly related, {\it without any} compactification. Amongst other predictions, we argue that LHC might be blind to new physics even if it comes at the TeV scale. In contrast, cosmic ray experiments, especially those that can register the very beginning of the shower, and collisions with high multiplicity and density of particles, might be sensitive to the dimensional cross-over.Comment: Published in Phys.Lett. B739 (2014) 117-12

    Collapsing objects with the same gravitational trajectory can radiate away different amount of energy

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    We study radiation emitted during the gravitational collapse from two different types of shells. We assume that one shell is made of dark matter and is completely transparent to the test scalar (for simplicity) field which belongs to the standard model, while the other shell is made of the standard model particles and is totally reflecting to the scalar field. These two shells have exactly the same mass, charge and angular momentum (though we set the charge and angular momentum to zero), and therefore follow the same geodesic trajectory. However, we demonstrate that they radiate away different amount of energy during the collapse. This difference can in principle be used by an asymptotic observer to reconstruct the physical properties of the initial collapsing object other than mass, charge and angular momentum. This result has implications for the information paradox and expands the list of the type of information which can be released from a collapsing object.Comment: 5 pages, 5 figures, accepted by PLB. arXiv admin note: text overlap with arXiv:1601.0792
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