1,721,181 research outputs found
Quantum Gravity and Predictions for our Universe
No full textIn this talk I provide an executive summary of some of the recent progress that has been made in understanding some key features of quantum gravitational theories. This is rooted in lessons learned from the landscape of consistent solutions to string theory and captured by the principles of the Swampland program. A key feature of this is the lack of decoupling between short and long distance descriptions of the theory leading to a radical revision of the notion of consistency of effective field theories. This opens up a new window into unresolved fine tuning problems for particle physics and cosmology. I will further explain how these ideas lead to concrete experimentally verifiable predictions for our universe.
Cumrun Vafa Cumrun Vafa is the Hollis Professor of Mathematicks and Natural Philosophy in the Physics Department at Harvard University, where he does research and teaches theoretical physics since 1985. Born in Iran in 1960, he moved to the US for higher education where he received his B.S. in math and physics from MIT before moving to Princeton University, where he received his Ph.D. in theoretical physics.
Coffee and tea served at 16:00pm</p
G(2) holonomy, Taubes' construction of Seiberg-Witten invariants and superconducting vortices
Full text linkUsing a reformulation of topological N = 2 QFT’s in M-theory setup, where QFT is realized via M5 branes wrapping co-associative cycles in a G2 manifold constructed from the space of self-dual 2-forms over a four-fold X, we show that superconducting vortices are mapped to M2 branes stretched between M5 branes. This setup provides a physical explanation of Taubes’ construction of the Seiberg-Witten invariants when X is symplectic and the superconducting vortices are realized as pseudo-holomorphic curves. This setup is general enough to realize topological QFT’s arising from N = 2 QFT’s from all Gaiotto theories on arbitrary 4-manifolds. © 2020, The Author(s)
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A stringy test of the fate of the conifold
No full textBy studying string loop corrections to the superpotential of Type LI strings compactified on Calabi-Yau threefolds we find a quantum stringy test and a confirmation of a recent proposal of Strominger on the fate of the conifold singularity, We also propose a connection between the spectrum of Bogomolnyi saturated solitons and the one-loop string partition function of N = 2 topological strings.Accepted Manuscrip
Ray-Singer Torsion, Topological Strings and Black Holes
Full text linkGenus one amplitude for topological strings on Calabi-Yau 3-folds can be
computed using mirror symmetry: The partition function at genus one gets mapped
to a holomorphic version of Ray-Singer torsion on the mirror Calabi-Yau. On the
other hand it can be shown by a physical argument that this gives a curvature
squared correction term to the gravitational action. This in paticular leads to
an effective quantum gravity cutoff known as the species scale, which varies
over moduli space of Calabi-Yau manifolds. This resolves some of the puzzles
associated to the entropy of small black holes when there are a large number of
light species of particles. Thus Ray-Singer torsion, via its connection to
topological strings at genus one, provides a measure of light degrees of
freedom of four dimensional N=2 supergravity theories. Based on a talk given on
May 12th, 2023 at the Singer Memorial Conference, MIT.Comment: 11 page
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Superstrings and topological strings at large N
No full textWe embed the large N Chern-Simons/topological string duality in ordinary superstrings. This corresponds to a large N duality between generalized gauge systems with N=1 supersymmetry in four dimensions and superstrings propagating on noncompact Calabi-Yau manifolds with certain fluxes turned on. We also show that in a particular limit of the N=1 gauge theory system, certain superpotential terms in the N=1 system (including deformations if spacetime is noncommutative) are captured to all orders in 1/N by the amplitudes of noncritical bosonic strings propagating on a circle with self-dual radius. We also consider D-brane/anti-D-brane system wrapped over vanishing cycles of compact Calabi-Yau manifolds and argue that at large N they induce a shift in the background to a topologically distinct Calabi-Yau, which we identify as the ground state system of the brane/anti-brane system.Accepted Manuscrip
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Instantons on D-branes
No full textWe consider type IIA compactification on K3. We show that the instanton subsectors of the worldvolume of N 4-branes wrapped around K3 lead to a Hagedorn density of BPS states in accord with heterotic-type IIA duality in 6 dimensions. We also find evidence that the correct framework to understand the results of Nakajima on the appearance of affine Kac-Moody algebras on the cohomology of moduli space of instantons on ALE spaces is in the context of heterotic-type IIA string duality.Accepted Manuscrip
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Extending Mirror Conjecture to Calabi–yau with Bundles
No full textWe define the notion of mirror of a Calabi-Yau manifold with a stable bundle in the context of type II strings in terms of supersymmetric cycles on the mirror. This allows us to relate the variation of Hedge structure for cohomologies arising from the bundle to the counting of holomorphic maps of Riemann surfaces with boundary on the mirror side. Moreover it opens up the possibility of studying bundles on Calabi-Yau manifolds in terms of supersymmetric cycles on the mirror.Accepted Manuscrip
String Phenomenology 2019
No full textI present some recent progress in formulating new swampland criteria
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Evidence for F-theory
No full textWe construct compact examples of D-manifolds for type IIB strings. The construction has a natural interpretation in terms of compactification of a 12-dimensional 'F-theory'. We provide evidence for a more natural reformulation of type IIB theory in terms of F-theory. Compactification of M-theory on a manifold K which admits elliptic fibration is equivalent to compactification of F-theory on K x S-1. A large class of N = 1 theories in 6 dimensions are obtained by compactification of F-theory on Calabi-Yau threefolds. A class of phenomenologically promising compactifications of F-theory is on Spin(7) holonomy manifolds down to 4 dimensions. This may provide a concrete realization of Witten's proposal for solving the cosmological constant problem in four dimensions.Accepted Manuscrip
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Gas of D-branes and Hagedorn density of BPS states
No full textWe test the prediction of a Hagedorn density of BPS states which carry RR charge in type II compactifications. We find that in certain cases they correspond to the supersymmetric ground states for a gas of identical 0-branes.Accepted Manuscrip
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