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Davide Gaiotto

Publications and source records attributed to Davide Gaiotto.

149 records · Page 9Linked to original sources
arXiv2003

Ghost Structure and Closed Strings in Vacuum String Field Theory

We complete the construction of vacuum string field theory by proposing a canonical choice of ghost kinetic term -- a local insertion of the ghost field at the string midpoint with an infinite normalization. This choice, supported by level expansion studies in the Siegel gauge, allows a simple analytic treatment of the ghost sector of the string field equations. As a result, solutions are just projectors, such as the sliver, of an auxiliary CFT built by combining the matter part with a twisted version of the ghost conformal theory. Level expansion experiments lead to surprising new projectors -- butterfly surface states, whose analytical expressions are obtained. With the help of a suitable open-closed string vertex we define open-string gauge invariant operators parametrized by on-shell closed string states. We use regulated vacuum string field theory to sketch how pure closed string amplitudes on surfaces without boundaries arise as correlators of such gauge invariant operators.

hep-th↗
arXiv2002

Experimental String Field Theory

We develop efficient algorithms for level-truncation computations in open bosonic string field theory. We determine the classical action in the universal subspace to level (18,54) and apply this knowledge to numerical evaluations of the tachyon condensate string field. We obtain two main sets of results. First, we directly compute the solutions up to level L=18 by extremizing the level-truncated action. Second, we obtain predictions for the solutions for L > 18 from an extrapolation to higher levels of the functional form of the tachyon effective action. We find that the energy of the stable vacuum overshoots -1 (in units of the brane tension) at L=14, reaches a minimum E_min = -1.00063 at L ~ 28 and approaches with spectacular accuracy the predicted answer of -1 as L -> infinity. Our data are entirely consistent with the recent perturbative analysis of Taylor and strongly support the idea that level-truncation is a convergent approximation scheme. We also check systematically that our numerical solution, which obeys the Siegel gauge condition, actually satisfies the full gauge-invariant equations of motion. Finally we investigate the presence of analytic patterns in the coefficients of the tachyon string field, which we are able to reliably estimate in the L -> infinity limit.

hep-th↗
arXiv2002

Star Algebra Projectors

Surface states are open string field configurations which arise from Riemann surfaces with a boundary and form a subalgebra of the star algebra. We find that a general class of star algebra projectors arise from surface states where the open string midpoint reaches the boundary of the surface. The projector property of the state and the split nature of its wave-functional arise because of a nontrivial feature of conformal maps of nearly degenerate surfaces. Moreover, all such projectors are invariant under constant and opposite translations of their half-strings. We show that the half-string states associated to these projectors are themselves surface states. In addition to the sliver, we identify other interesting projectors. These include a butterfly state, which is the tensor product of half-string vacua, and a nothing state, where the Riemann surface collapses.

hep-th↗
arXiv2002

Patterns in Open String Field Theory Solutions

In open string field theory the kinetic operator mixes matter and ghost sectors, and thus the ghost structure of classical solutions is not universal. Nevertheless, we have found from numerical analysis that certain ratios of expectation values for states involving pure ghost excitations appear to be universal. We give an analytic expression for these ratios and find good evidence that they are common to all known solutions of open string field theory, including the tachyon vacuum solution, lump solutions and string fields representing marginal deformations. We also draw attention to a close correspondence between the expectation values for the pure matter components in the tachyon vacuum solution and those in the solution of a simpler equation for a ghost number zero string field. Finally we observe that the action of L_0 on the tachyon condensate gives a state that is approximately factorized into a matter and a ghost part.

hep-th↗