arXiv subjects
Publications and source records attributed to Warren Siegel.
We propose stringy hadronic amplitudes that combine some of the features of sister trajectories and running tension. By summing over string amplitudes with varying Regge trajectories that have integer tension and converging intercept, we obtain parton hard-scattering and Regge soft-scattering behaviors, while preserving discrete poles in both momentum and angular momentum.
S-matrices can be written Lorentz covariantly in terms of free field strengths for vector states, allowing arbitrary gauge choices. In string theory the vertex operators can be chosen so this gauge invariance is automatic. As examples we give four-vector (super)string tree amplitudes in this form, and find the field theory actions that give the first three orders in the slope.
We show that unlike conventional field theory, the particle field theory of the string's constituents produces in the ladder approximation linear Regge trajectories, in accord with its string theory dual. In this theory propagators are Gaussian and this feature facilitates the perturbative evaluation of scattering amplitudes. We develop general techniques for studying their general asymptotic form. We consider radiative corrections to the ladder Regge trajectory and discover that linearity is lost; however, this may be due to certain approximations we have made.
The twistor superstring, which describes N=4 super Yang-Mills trees, is taken off-shell (for loops) by generalizing Penrose twistors (which describe on-shell momenta) to Atiyah-Drinfel'd-Hitchin-Manin twistors (which include the usual spacetime coordinates). The resulting string is then shown to be the tensionless limit of a Quantum ChromoDynamics-like superstring.
We generalize the construction of Snyder to a Lorentz covariant noncommutative superspace.
We derive Yang-Mills vertex operators for (super)string theory whose BRST invariance requires only the free gauge-covariant field equation and no gauge condition. Standard conformal field theory methods yield the three-point vertices directly in gauge-invariant form.
In certain Lorentz-covariant higher-derivative field theories of spins < or =1, would-be ultraviolet divergences generate color-singlet poles as infrared divergences. Absence of higher-order poles implies ten-dimensional supersymmetric Yang-Mills with bound-state supergravity, in close analogy with open string theory.
We re-examine the projective lightcone limit of the gauge-invariant Green-Schwarz action on 5D anti-de Sitter x the five-sphere. It implies the usual holography for AdS5, but also (a complex) one for S5. The result is N=4 projective superspace, which unlike N=4 harmonic superspace can describe N=4 super Yang-Mills off shell.
We propose a new form of dimensional reduction that constrains dilatation instead of a component of momentum. It corresponds to replacing toroidal compactification in a Cartesian coordinate with that in the logarithm of the radius. Massive theories in de Sitter or anti de Sitter space are thus produced from massless (scale invariant) theories in one higher space or time dimension. As an example, we derive free massive actions for arbitrary representations of the (anti) de Sitter group in arbitrary dimensions. (Previous general results were restricted to symmetric tensors.) We also discuss generalizations to interacting theories.
Covariant quantization of self-dual strings in 2+2 flat dimensions reduces them to their zero modes, a consequence of extended world-sheet supersymmetry. We demonstrate how to arrive at the same result more directly by employing a `double' light-cone gauge. An unconventional feature of this gauge is the removal of anticommuting degrees of freedom by commuting symmetries and vice versa. The reducibility of the N=4 string and its equivalence with the N=2 string become apparent.
In this paper we develop the formalism to study superforms in N=2 harmonic superspace. We perform a thorough (if not complete) analysis of the superforms starting from 0-form and moving all the way up to 6-form. Like the N=1 case we find that the lower superforms (0,1,2,3) describe the various important N=2 supermultiplets. Also, the forms form chains, the field strength of 0-form being related to the gauge form of the 1-form, and so on. However, an important difference with the N=1 case is that there is now more than one chain. Our main aim was to study the higher-forms (4,5,6) to obtain the various N=2 action formulas via the ectoplasmic approach. Indeed, we reproduce the three known action formulas involving a volume integral, a contour integral and no integral over the harmonic subspace from the 6, 5 and 4-form analysis respectively. The next aim is to generalize the analysis to curved space-time (supergravity).
A T-dualized selfdual inspired formulation of massive vector fields coupled to arbitrary matter is generated; subsequently its perturbative series modeling a spontaneously broken gauge theory is analyzed. The new Feynman rules and external line factors are chirally minimized in the sense that only one type of spin index occurs in the rules. Several processes are examined in detail and the cross-sections formulated in this approach. A double line formulation of the Lorentz algebra for Feynman diagrams is produced in this formalism, similar to color ordering, which follows from a spin ordering of the Feynman rules. The new double line formalism leads to further minimization of gauge invariant scattering in perturbation theory. The dualized electroweak model is also generated.
We derive the Green-Schwarz action on AdS_5 x S^5 using an alternate version of the coset superspace construction. By Wick rotations and Lie algebra identifications we bring the coset to GL(4|4)/(Sp(4) x GL(1))^2, which allows us to represent the conformal transformations on unconstrained matrices. The derivation is more streamlined even for the bosonic sector, and conformal symmetry is manifest at every step. Kappa-symmetry gauge fixing is more transparent.
We show the existence of a global anomaly in the one-loop graphs of N=2 string theory, defined by sewing tree amplitudes, unless spacetime supersymmetry is imposed. The anomaly is responsible for the non-vanishing maximally helicity violating amplitudes. The supersymmetric completion of the N=2 string spectrum is formulated by extending the previous cohomological analysis with an external spin factor; the target space-time spin-statistics of these individual fields in a selfdual background are compatible with previous cohomological analysis as fields of arbitrary spin may be bosonized into one another. We further analyze duality relations between the open and closed string amplitudes and demonstrate this in the supersymmetric extension of the target space-time theory through the insertion of zero-momentum operators.
We consider a geometric zero-radius limit for strings on $AdS_5\times S^5$, where the anti-de Sitter hyperboloid becomes the projective lightcone. In this limit the fifth dimension becomes nondynamical, yielding a different "holographic" interpretation than the usual "bulk to boundary" one. When quantized on the random lattice, the fifth coordinate acts as a new kind of Schwinger parameter, producing Feynman rules with normal propagators at the tree level: For example, in the bosonic case ordinary massless $ϕ^4$ theory is obtained. In the superstring case we obtain new, manifestly ${\cal N}=4$ supersymmetric rules for ${\cal N}=4$ super Yang-Mills. These gluons are also different from those of the usual AdS/CFT correspondence: They are the "partons" that make up the usual "hadrons" of the open and closed strings in the familiar QCD string picture. Thus, their coupling $g_{YM}$ and rank $N$ of the "color" gauge group are different from those of the "flavor" gauge group of the open string. As a result we obtain different perturbation expansions in radius, coupling, and 1/N.
We introduce a self-dual field strength which replaces the gauge field in spontaneously broken Yang-Mills theory, reformulating it as a Lorentz covariant non-linear sigma model. This dualized theory is in both a unitary and renormalizable gauge: The self-dual field strength has exactly the three components necessary to describe a massive vector field. In future work we shall utilize this new formulation as a calculational tool in spontaneously broken gauge theories.
Manifestly Lorentz covariant Feynman rules are given in terms of a "scalar" field for each helicity, dramatically simplifying the calculation of amplitudes with massless particles. The spinor helicity formalism is properly identified as a null complex spacelike (not lightlike) gauge, where two massless external momenta define the reference frame. Usually this gauge is applied only to external line factors; we extend this method to vertices and propagators by modifying the action itself using lightcone methods.
We give efficient superspace methods for deriving component actions for supergravity coupled to matter. One method uses normal coordinates to covariantly expand the superfield action, and can be applied straightforwardly to any superspace. The other interprets the component lagrangian as a differential form on a bosonic hypersurface in superspace, and gives a simple derivation for pertinent cases such as chiral superspace.