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Register a new userThe birth of string theory
بدء نظرية الحبل
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Authors
Paolo Di Vecchia
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في هذا المساهمة، نذهب من خلال التطورات التي أدت من نموذج فينيزيانو إلى الحبل البوزوني في السنوات 1968 إلى 1974.
In this contribution we go through the developments that in the years 1968 to 1974 led from the Veneziano model to the bosonic string.
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Invited contribution to the collective book The Birth of String Theory
In this review article, we first discuss a possible regularization of the big bang curvature singularity of the standard Friedmann cosmology, where the curvature singularity is replaced by a spacetime defect. We then consider the hypothesis that a new physics phase gave rise to this particular spacetime defect. Specifically, we set out on an explorative calculation using the IIB matrix model, which has been proposed as a particular formulation of nonperturbative superstring theory (M-theory).
We comment on the relation between string theory and empirical science, grounding our discussion in cosmology, a subject with increasingly precise data in which this connection operates at several levels. It is important to take into account the phenomenon of dangerous irrelevance: over long times or large field ranges, physics can become sensitive to higher scales than the input energies. This pertains in inflationary cosmology (and possibly other aspects of horizon physics). String theory also contributes to our understanding of observational constraints and search strategies at the level of low energy field theory. We illustrate this with a current example concerning a new form of non-Gaussianity generated by very massive degrees of freedom coupling to the inflaton. New constraints on such fields and couplings can be obtained from existing data, increasing our empirical knowledge of the universe. This builds in part from the development of the string landscape, which is neither random nor an abdication of science as has sometimes been suggested. {it Invited contribution to the proceedings of the conference `Why trust a theory.}
In this note, we study the deformation of the topological string by $barOmega$. Namely, adopting the perturbative string amplitudes approach, we identify the $barOmega$-deformation in terms of a physical state in the sting spectrum. We calculate the topological amplitudes $F_g$ in heterotic string theory in the presence of the latter. In particular, we show that it is crucial to include quadratic terms in the effective action in order for $barOmega$ to decouple. It turns out that this decoupling happens at the full string level, suggesting that this holds non-perturbatively.
We perform an extensive analysis of the statistics of axion masses and interactions in compactifications of type IIB string theory, and we show that black hole superradiance excludes some regions of Calabi-Yau moduli space. Regardless of the cosmological model, a theory with an axion whose mass falls in a superradiant band can be probed by the measured properties of astrophysical black holes, unless the axion self-interaction is large enough to disrupt formation of a condensate. We study a large ensemble of compactifications on Calabi-Yau hypersurfaces, with $1 leq h^{1,1} leq 491$ closed string axions, and determine whether the superradiance conditions on the masses and self-interactions are fulfilled. The axion mass spectrum is largely determined by the Kahler parameters, for mild assumptions about the contributing instantons, and takes a nearly-universal form when $h^{1,1} gg 1$. When the Kahler moduli are taken at the tip of the stretched Kahler cone, the fraction of geometries excluded initially grows with $h^{1,1}$, to a maximum of $approx 0.5$ at $h^{1,1} approx 160$, and then falls for larger $h^{1,1}$. Further inside the Kahler cone, the superradiance constraints are far weaker, but for $h^{1,1} gg 100$ the decay constants are so small that these geometries may be in tension with astrophysical bounds, depending on the realization of the Standard Model.
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