arXiv subjects

Michael Kroyter

Publications and source records attributed to Michael Kroyter.

26 records · Page 2Linked to original sources

arXiv2006

Schnabl's L_0 Operator in the Continuous Basis

Following Schnabl's analytic solution to string field theory, we calculate the operators ${\cal L}_0,{\cal L}_0^\dagger$ for a scalar field in the continuous $κ$ basis. We find an explicit and simple expression for them that further simplifies for their sum, which is block diagonal in this basis. We generalize this result for the bosonized ghost sector, verify their commutation relation and relate our expressions to wedge state representations.

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arXiv2006

On the validity of the solution of string field theory

We analyze the realm of validity of the recently found tachyon solution of cubic string field theory. We find that the equation of motion holds in a non trivial way when this solution is contracted with itself. This calculation is needed to conclude the proof of Sen's first conjecture. We also find that the equation of motion holds when the tachyon or gauge solutions are contracted among themselves.

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arXiv2005

Normalization anomalies in level truncation calculations

We test oscillator level truncation regularization in string field theory by calculating descent relations among vertices, or equivalently, the overlap of wedge states. We repeat the calculation using bosonic, as well as fermionic ghosts, where in the bosonic case we do the calculation both in the discrete and in the continuous basis. We also calculate analogous expressions in field level truncation. Each calculation gives a different result. We point out to the source of these differences and in the bosonic ghost case we pinpoint the origin of the difference between the discrete and continuous basis calculations. The conclusion is that level truncation regularization cannot be trusted in calculations involving normalization of singular states, such as wedge states, rank-one squeezed state projectors and string vertices.

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arXiv2004

On surface states and star-subalgebras in string field theory

We elaborate on the relations between surface states and squeezed states. First, we investigate two different criteria for determining whether a matter sector squeezed state is also a surface state and show that the two criteria are equivalent. Then, we derive similar criteria for the ghost sector. Next, we refine the criterion for determining whether a surface state is in H_{κ^2}, the subalgebra of squeezed states obeying [S,K_1^2]=0. This enables us to find all the surface states of the H_{κ^2} subalgebra, and show that it consists only of wedge states and (hybrid) butterflies. Finally, we investigate generalizations of this criterion and find an infinite family of surface states subalgebras, whose surfaces are described using a "generalized Schwarz-Christoffel" mapping.

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arXiv2003

Continuous Half-String Representation of String Field Theory

We give the explicit form of the half-string representation in the continuous kappa basis. We show the comma structure of the three-vertex, when expanded around an arbitrary projector, and that the zero-mode must be replaced by the mid-point degree of freedom in the half-string representation. The treatment of the ghost sector enables us to calculate the normalization of the vertices. The simplicity of this formalism is demonstrated with some applications, such as gauge transformations and identification of subalgebras.

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arXiv2002

Virasoro operators in the continuous basis of string field theory

In this work we derive two important tools for working in the κbasis of string field theory. First we give an analytical expression for the finite part of the spectral density ρ_{fin}. This expression is relevant when both matter and ghost sectors are considered. Then we calculate the form of the matter part of the Virasoro generators L_n in the κbasis, which construct string field theory's derivation Q_{BRST}. We find that the Virasoro generators are given by one dimensional delta functions with complex arguments.

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arXiv2002

Squeezed State Projectors in String Field Theory

We find a new subalgebra of the star product in the matter sector. Its elements are squeezed states whose matrices commute with (K_1)^2. This subalgebra contains a large set of projectors. The states are represented by their eigenvalues and we find a mapping between the eigenvalues representation and other known representations. The sliver is naturally in this subalgebra. Surprisingly, all the generalized butterfly states are also in this subalgebra, enabling us to analyze their spectrum, and to show the orthogonality of different butterfly states. This means that multi D-brane states can be built of butterfly states.

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arXiv2000

On the Spatial Structure of Monopoles

We study the spatial structure of 1/4 BPS solitons in 4 dimensional N=4 gauge theory. A weak binding approximation is used where the soliton is made of several "ingredient" particles. Some spatial moduli are described which are not accounted for in the (p,q) web picture. These moduli are counted and their effect on the solutions is demonstrated. The potential for off BPS configurations is estimated by a simple expression and is found to agree with previous expressions. We discuss the fermionic zero modes of the solitons, and find agreement with web predictions.

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