arXiv subjects

Warren Siegel

Publications and source records attributed to Warren Siegel.

At least 19 recordsLinked to original sources

arXiv2023

Left-handed string and CHY amplitude at one loop

We propose a generalized left-handed (chiral) gauge choice for the genus one Riemann surface, realized through a singular gauge transformation of worldsheet coordinates. The transformation predominantly affects the logarithmic non-zero modes of the Green's function, leaving non-holomorphic and non-logarithmic modes unchanged. This procedure yields $δ$-functions for chiral coordinates and box-diagram-like integrals in terms of modular parameters. The resulting $δ$-functions formulate one-loop level Scattering Equations that simplify to satisfy the tree-level solutions, constraining the locations of the marked points. Subsequent integrals agree with the field-theoretic box diagram for the four-point amplitude, in accordance with the divergent $ε$ expansions derived from dimensional regularization in the infrared limit. We conclude by highlighting potential avenues for future research, including the exploration of methodologies that preclude the need for worldsheet coordinates reparametrization and their implications for accurately capturing infrared behavior from modular parameter integrals.

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arXiv2022

Remarks on the critical dimension of left-handed string and its quasiconformal nature

The chiral string without a singular gauge limit is argued to have the same critical dimension as its corresponding conventional closed string. Thus, its central charge would be the same as its conventional counterpart in the conformal gauge. Here, we would re-examine the critical dimension of the chiral string in the singular Hohm-Siegel-Zwiebach limit. A straight forward calculation of the operator product expansion (OPE) of the corresponding would-be stress tensor shows that the central charge term is not the same as its conventional counterpart when taking the singular limit. Instead of having a conformal transformation on the worldsheet, the coordinate reparametrization provides a set of quasiconformal mappings.

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arXiv2022

Open F-branes

We include in F-theory, through open Type I F-theory branes (F-branes), string theories with N = 1 supersymmetry, both Type I and heterotic. Type I branes are distinguished from Type II by worldvolume parity projection. The same open Type I branes describe both open Type I superstrings and closed heterotic upon different sectionings from F-branes to worldsheets, while closed Type I superstrings arise from closed Type I branes. (Type II superstrings come from closed Type II branes, as described previously.) F-theory manifests the exceptional-group U-duality symmetry, with all massless bosonic fields in a single gauge coset. This coset branches to the usual bosonic supergravity fields upon sectioning. We examine in detail the simple case of D = 3 F-theory: Parity projection reduces the Type II coset SL(5)/SO(3,2) to the Type I coset SO(3,3)/SO(2,1)2 = SL(4)/SO(2,2).

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arXiv2021

Perturbative F-theory 10-brane and M-theory 5-brane

The exceptional symmetry is realized perturbatively in F-theory which is the manifest U-duality theory. The SO(5,5) U-duality symmetry acts on both the 16 spacetime coordinates and the 10 worldvolume coordinates. Closure of the Virasoro algebra requires the Gauss law constraints on the worldvolume. This set of current algebras describes a F-theory 10-brane. The SO(5,5) duality symmetry is enlarged to the SO(6,6) in the Lagrangian formulation. We propose actions of the F-theory 10-brane with SO(5,5) and SO(6,6) symmetries. The gauge fields of the latter action is coset elements of SO(6,6)/SO(6;C) which includes both the SO(5,5)/SO(5;C) spacetime backgrounds and the worldvolume backgrounds. The SO(5,5) current algebra obtained from the Pasti-Sorokin-Tonin M5-brane Lagrangian leads to the theory behind M-theory, namely F-theory. We also propose an action of the perturbative M-theory 5-brane obtained by sectioning the worldvolume of the F-theory 10-brane.

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arXiv2021

Chiral string theories as an interpolation between strings and particles

A new set of boundary conditions for string propagators is proposed in this paper. The boundary conditions are parametrized by a complex number $λ$. Under these new boundary conditions, the left-moving and right-moving modes are treated unequally. Thus, we called them chiral string theories. If $λ= -1$, the spectrum of such theory truncates to a finite number, and therefore it becomes a different description of supergravity. We found the spectrum of chiral string theories by requiring that the vertex operators are conformally invariant. In addition, we also calculate the amplitudes for arbitrary $λ$. The amplitudes are expressed as a product of open string amplitudes which are similar to the KLT relation. The unitarity of these theories are investigated. However, we found out that except for $λ= \pm 1$, all other theories are not unitary; i.e., only the supergravity and ordinary strings are unitary. Although most of the chiral strings are not physical, they still serve as a valuable tool in studying the relation between particle theories and string theories.

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arXiv2020

S-matrices from 4d worldvolume

We give an example of how conformal field theory methods in worldvolumes of dimension d > 2 could be used to calculate string-like amplitudes. The worldvolume propagator's logarithmic behavior is based on the use of worldvolume superspace (rather than the worldvolume ghost coordinates of a previous paper). Massless states have maximum spin d. Unitarity is not studied. We also touch on some related topics for ordinary spinning strings: calculating closed-string trees in worldsheet superspace, and zeroth-quantization of OSp(1|2) with zero-mode ghosts only.

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arXiv2020

F-theory amplitudes

We propose 4-point S-matrices for three-dimensional F-theory. We will use the twistor formalism to facilitate constructing the amplitude. We write the amplitude in a way such that the F-symmetry (U-duality symmetry) is manifest. The amplitude can be schematically written as $A_{4} = w^{4}/stu$, where $w$ is an analog of the linearized Weyl tensor in F-theory, and $w^{4}$ is a shorthand for the sum of various contractions that can happen between the Weyl tensors. The gauge invariance is actually non-trivial since $w$ is in general not gauge invariant. With the help of the twistor formalism, one can verify that this formula is indeed gauge invariant. The amplitude also reduces to the ordinary 4-graviton amplitude under the reduction to M-theory (which is just 4D supergravity).

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arXiv2020

M Theory from F Theory

We write down a $GL(D+1)$ (D for the dimension of string theory) manifest fundamental brane worldvolume current algebra description of M theory, which consists of a pair of vector field $X^m$ and dual 2-form field $X_{mn}$, compositing together to parametrize the spacetime, with a selfduality condition for sectioning. The worldvolume of the brane itself is a (D+2) dimensional object, and the background spacetime after sectioning has dimension (D+1). We summarize the features of the algebra. The field contents of the corresponding background geometry, the usual vielbein $e_a{}^m$ and the 3-form $A_{mnp}$, could be identified as different blocks of the composite spacetime vielbein, by solving the orthogonality condition. Their behaviour under gauge transformation are also determined by the corresponding rules of the composite vielbein. Then by solving F theory $\mathcal{V}$ constraints, we reduce the number of worldvolume and show how to recover M theory from F theory.

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arXiv2020

Simplifying 4d $\mathcal{N}=3$ Harmonic Superspace

We quantize super Yang-Mills action in $\mathcal{N}=3$ harmonic superspace using "Fermi-Feynman" gauge and also develop the background field formalism. This leads to simpler propagators and Feynman rules that are useful in performing explicit calculations. The superspace rules are used to show that divergences do not appear at 1-loop and beyond. We also compute a finite contribution to the effective action from a 4-point diagram at 1-loop, which matches the expected covariant result.

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arXiv2020

T-dual Superstring Lagrangian with double zweibeins

We present superstring Lagrangians with manifest T-duality. The Lagrangian version of the section conditions are necessary to make Lagrangians to be general coordinate invariant. We show the general solution of section conditions. The D-dimensional left and right moving currents are the 2D-dimensional chiral current which causes the chiral boson problem. We solve the problem by adding the unphysical 2D-dimensional anti-selfdual current with the selfduality constraints. The Lagrange multipliers of the selfduality constraints play the role of the worldsheet zweibein allowing the Weyl invariant and Lorentz symmetric worldsheet. Doubling the zweibein makes the type II kappa-symmetry splitting into two sets of the type I kappa-symmetries.

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arXiv2019

F-theory superspace backgrounds

F-theory is the theory proposed to incorporate superstring theory in a way such that STU dualities are manifest. A useful description uses a current superalgebra on a higher-dimensional worldvolume, following from an action for a selfdual gauge field. Here the group "metric" appearing in the Schwinger (central charge) term of this current superalgebra is generalized to a tensor, in analogy to the usual generalization of the structure constants to the torsion (and curvature). This allows introduction of a massless background describing F-supergravity on the original bosonic worldvolume. The isotropy group is represented on superspace, while the (exceptional) symmetry is represented on the worldvolume. As an example, we solve off shell the linearized superspace constraints of the massless sector of the F-theory that generalizes the N=2 supergravity (+ matter) of 3D S(tring)-theory, the corresponding manifestly T-dual theory of T-theory, and the N=1 supergravity of 4D M-theory. The results for the prepotential, its gauge transformation, and action agree with those that were derived previously without reference to the current algebra of the full F-theory.

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arXiv2019

O(D,D) gauge fields in the T-dual string Lagrangian

We present the string Lagrangian with manifest T-duality. Not only zero-modes but also all string modes are doubled. The gravitational field is an O(D,D) gauge field. We give a Lagrangian version of the section condition for the gauge invariance which compensates the O(D,D) transformation from the gravitational field and the GL(2D) coordinate transformation. We also show the gauge invariance of the line element of the manifest T-duality space and the O(D,D) condition on the background. Different sections describe dual spaces.

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arXiv2018

Enlarged exceptional symmetries of first-quantized F-theory

The exceptional symmetries of supergravity have been reproduced from the Hamiltonian formulation of the classical mechanics of F-theory. We now find the Lagrangian formalism has even larger exceptional symmetries, simplifying its derivation: We discuss D = 5 as an example.

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arXiv2017

F-brane Superspace: The New World Volume

F-theory requires a new Virasoro algebra, including $κ$-symmetry, with a worldvolume coordinate for each generator. (Similar is implied for the superstring.) Doubles of the spacetime coordinates are eliminated by selfduality, which now applies to all currents.

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arXiv2017

Manifestly T-dual formulation of AdS space

We present a manifestly T-dual formulation of curved spaces such as an AdS space. For group manifolds related by the orthogonal vielbein fields the three form H=dB in the doubled space is universal at least locally. We construct an affine nondegenerate doubled bosonic AdS algebra to define the AdS space with the Ramond-Ramond flux. The non-zero commutator of the left and right momenta leads to that the left momentum is in an AdS space while the right momentum is in a dS space. Dimensional reduction constraints and the physical AdS algebra are shown to preserve all the doubled coordinates.

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arXiv2017

Chiral Superstring and CHY Amplitude

We calculate the chiral string amplitude in pure spinor formalism and take four point amplitude as an example. The method could be easily generalized to $N$ point amplitude by complicated calculations. By doing the usual calculations of string theory first and using a special singular gauge limit, we produce the amplitude with the integral over Dirac $δ$-functions. The Bosonic part of the amplitude matches the CHY amplitude and the Fermionic part gives us the supersymmetric generalization of CHY amplitude. Finally, we also check the dependence on boundary condition for heterotic chiral string amplitudes.

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arXiv2017

Chiral Closed strings: Four massless states scattering amplitude

We compute the scattering amplitudes of four massless states for chiral (closed) bosonic and type II superstrings using the Kawai-Lewellen-Tye ($KLT$) factorization method. The amplitude in the chiral bosonic case is identical to a field theory amplitude corresponding to the spin-$2$ tachyon, massless gravitational sector and massive spin-2 tardyon states of the spectrum. Chiral type II superstrings amplitude only possess poles associated with the massless gravitational sector. We briefly discuss the extension of the calculation to heterotic superstrings.

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arXiv2016

Critical Super F-theories

We present F-theories that reduce to 10D Type II Green-Schwarz superstrings. They vary in manifest U-duality according to division between spacetime and "internal" coordinates. They are defined by selfdual current superalgebras in higher worldvolume dimensions with manifest $\mathrm G\times \mathrm G'$ symmetry where the spacetime symmetry $\mathrm G=\mathrm E_{n(n)}$ ranges over the (split form of the) exceptional groups with ranks $n=\mathrm D+1 \leq 7$ and the internal symmetry $\mathrm {G'= GL(10-D)}$.

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