arXiv subjects

Marcus Spradlin

Publications and source records attributed to Marcus Spradlin.

At least 91 records · Page 5Linked to original sources

arXiv2008

Three-Loop Leading Singularities and BDS Ansatz for Five Particles

We use the leading singularity technique to determine the planar three-loop five-particle amplitude in N=4 super Yang-Mills in terms of a simple basis of integrals. We analytically compute the integral coefficients for both the parity-even and the parity-odd parts of the amplitude. The parity-even part involves only dual conformally invariant integrals. Using the method of obstructions we numerically evaluate two previously unfixed coefficients which appear in the three-loop BDS ansatz.

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arXiv2007

Scattering of single spikes

We apply the dressing method to a string solution given by a static string wrapped around the equator of a three-sphere and find that the result is the single spike solution recently discussed in the literature. Further application of the method allows the construction of solutions with multiple spikes. In particular we construct the solution describing the scattering of two single spikes and compute the scattering phase shift. As a function of the dressing parameters, the result is exactly the same as the one for the giant magnon, up to non-logarithmic terms. This suggests that the single spikes should be described by an integrable spin chain closely related to the one associated to the giant magnons. The field theory interpretation of such spin chain however is still unclear.

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arXiv2007

Four-Loop Collinear Anomalous Dimension in N = 4 Yang-Mills Theory

We report a calculation in N = 4 Yang-Mills of the four-loop term g^4 in the collinear anomalous dimension g(lambda) which governs the universal subleading infrared structure of gluon scattering amplitudes. Using the method of obstructions to extract this quantity from the 1/epsilon singularity in the four-gluon iterative relation at four loops, we find g^4 = -1240.9 with an estimated numerical uncertainty of 0.02%. We also analyze the implication of our result for the strong coupling behavior of g(lambda), finding support for the string theory prediction computed recently by Alday and Maldacena using AdS/CFT.

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arXiv2007

New Dual Conformally Invariant Off-Shell Integrals

Evidence has recently emerged for a hidden symmetry of scattering amplitudes in N=4 super Yang-Mills theory called dual conformal symmetry. At weak coupling the presence of this symmetry has been observed through five loops, while at strong coupling the symmetry has been shown to have a natural interpretation in terms of a T-dualized AdS_5. In this paper we study dual conformally invariant off-shell four-point Feynman diagrams. We classify all such diagrams through four loops and evaluate 10 new off-shell integrals in terms of Mellin-Barnes representations, also finding explicit expressions for their infrared singularities.

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arXiv2007

Dressing the Giant Gluon

We demonstrate the applicability of the dressing method to the problem of constructing new classical solutions for Euclidean worldsheets in anti-de Sitter space. The motivation stems from recent work of Alday and Maldacena, who studied gluon scattering amplitudes at strong coupling using a generalization of a particular worldsheet found by Kruczenski whose edge traces a path composed of light-light segments on the boundary of AdS. We dress this `giant gluon' to find new solutions in AdS_3 and AdS_5 whose edges trace out more complicated, timelike curves on the boundary. These solutions may be used to calculate certain Wilson loops via AdS/CFT.

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arXiv2007

Semiclassical Quantization of the Giant Magnon

Solitons in field theory provide a window into regimes not directly accessible by the fundamental perturbative degrees of freedom. Motivated by interest in the worldsheet S-matrix of string theory in AdS_5 x S^5 in the limit of infinite worldsheet volume we consider the semiclassical quantization of a particular soliton of this theory: the Hofman-Maldacena `giant magnon' spinning string. We obtain explicit formulas for the complete spectrum of bosonic and fermionic fluctuations around the giant magnon. As an application of these results we confirm that the one-loop correction to the classical energy vanishes as expected.

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arXiv2007

Four-Loop Cusp Anomalous Dimension From Obstructions

We introduce a method for extracting the cusp anomalous dimension at L loops from four-gluon amplitudes in N=4 Yang-Mills without evaluating any integrals that depend on the kinematical invariants. We show that the anomalous dimension only receives contributions from the obstructions introduced in hep-th/0601031. We illustrate this method by extracting the two- and three-loop anomalous dimensions analytically and the four-loop one numerically. The four-loop result was recently guessed to be f^4 = - (4ζ^3_2+24ζ_2ζ_4+50ζ_6- 4(1+r)ζ_3^2) with r=-2 using integrability and string theory arguments in hep-th/0610251. Simultaneously, f^4 was computed numerically in hep-th/0610248 from the four-loop amplitude obtaining, with best precision at the symmetric point s=t, r=-2.028(36). Our computation is manifestly s/t independent and improves the precision to r=-2.00002(3), providing strong evidence in favor of the conjecture. The improvement is possible due to a large reduction in the number of contributing terms, as well as a reduction in the number of integration variables in each term.

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arXiv2007

Dressing the Giant Magnon

We apply the dressing method to construct new classical string solutions describing various scattering and bound states of magnons. These solutions carry one, two or three SO(6) charges and correspond to multi-soliton configurations in the generalized sine-Gordon models.

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arXiv2006

Dressing the Giant Magnon II

We extend our earlier work by demonstrating how to construct classical string solutions describing arbitrary superpositions of scattering and bound states of dyonic giant magnons on S^5 using the dressing method for the SU(4)/Sp(2) coset model. We present a particular scattering solution which generalizes solutions found in hep-th/0607009 and hep-th/0607044 to the case of arbitrary magnon momenta. We compute the classical time delay for the scattering of two dyonic magnons carrying angular momenta with arbitrary relative orientation on the S^5.

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arXiv2006

String Theory in Beta Deformed Spacetimes

Fluxbrane-like backgrounds obtained from flat space by a sequence of T-dualities and shifts of polar coordinates (beta deformations) provide an interesting class of exactly solvable string theories. We compute the one-loop partition function for various such deformed spaces and study their spectrum of D-branes. For rational values of the B-field these models are equivalent to Z_N \times Z_N orbifolds with discrete torsion. We also obtain an interesting new class of time-dependent backgrounds which resemble localized closed string tachyon condensation.

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arXiv2006

All Split Helicity Tree-Level Gluon Amplitudes

Recently a new recursion relation for tree-level gluon amplitudes in gauge theory has been discovered. We solve this recursion to obtain explicit formulas for the closed set of amplitudes with arbitrarily many positive and negative helicity gluons in a split helicity configuration. The solution admits a simple diagrammatic expansion in terms of zigzag diagrams. We comment on generalizations of this result.

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arXiv2006

Hidden Beauty in Multiloop Amplitudes

Planar L-loop maximally helicity violating amplitudes in N = 4 supersymmetric Yang-Mills theory are believed to possess the remarkable property of satisfying iteration relations in L. We propose a simple new method for studying the iteration relations for four-particle amplitudes which involves the use of certain linear differential operators and eliminates the need to fully evaluate any loop integrals. We carry out this procedure in explicit detail for the two-loop amplitude and argue that this method can be used to prove the iteration relations to all loops up to polynomials in logarithms.

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arXiv2006

Iterative Structure Within The Five-Particle Two-Loop Amplitude

We find an unexpected iterative structure within the two-loop five-gluon amplitude in N = 4 supersymmetric Yang-Mills theory. Specifically, we show that a subset of diagrams contributing to the full amplitude, including a two-loop pentagon-box integral with nontrivial dependence on five kinematical variables, satisfies an iterative relation in terms of one-loop scalar box diagrams. The implications of this result for the possible iterative structure of the full two-loop amplitude are discussed.

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arXiv2004

Dissolving N=4 loop amplitudes into QCD tree amplitudes

We use the infrared consistency of one-loop amplitudes in N=4 Yang-Mills theory to derive a compact analytic formula for a tree-level NNMHV gluon scattering amplitude in QCD, the first such formula known. We argue that the IR conditions, coupled with recent advances in calculating one-loop box coefficients, can give a new tool for computing tree-level amplitudes in general. Our calculation suggests that many amplitudes have a structure which is even simpler than that revealed so far by current twistor-space constructions.

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arXiv2004

A Pendant for Polya: The One-Loop Partition Function of N=4 SYM on R x S^3

We study weakly coupled SU(N) N = 4 super Yang-Mills theory on R x S^3 at infinite N, which has interesting thermodynamics, including a Hagedorn transition, even at zero Yang-Mills coupling. We calculate the exact one-loop partition function below the Hagedorn temperature. Our calculation employs the representation of the one-loop dilatation operator as a spin chain Hamiltonian acting on neighboring sites and a generalization of Polya's counting of `necklaces' (gauge-invariant operators) to include necklaces with a `pendant' (an operator which acts on neighboring beads). We find that the one-loop correction to the Hagedorn temperature is delta ln T_H = + lambda/8 pi^2.

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arXiv2004

Two-Loop Partition Function in the Planar Plane-Wave Matrix Model

We perform two independent calculations of the two-loop partition function for the large N 't Hooft limit of the plane-wave matrix model, conjectured to be dual to the decoupled little string theory of a single spherical type IIA NS5-brane. The first is via a direct two-loop path-integral calculation in the matrix model, while the second employs the one-loop dilatation operator of four-dimensional N = 4 Yang-Mills theory truncated to the SU(2|4) subsector. We find precise agreement between the results of the two calculations. Various polynomials appearing in the result have rather special properties, possibly related to the large symmetry algebra of the theory or to integrability.

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arXiv2004

A Googly Amplitude from the B-model in Twistor Space

Recently it has been proposed that gluon scattering amplitudes in gauge theory can be computed from the D-instanton expansion of the topological B-model on P^{3|4}, although only maximally helicity violating (MHV) amplitudes have so far been obtained from a direct B-model calculation. In this note we compute the simplest non-MHV gluon amplitudes (++--- and +-+--) from the B-model as an integral over the moduli space of degree 2 curves in P^{3|4} and find perfect agreement with Yang-Mills theory.

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arXiv2004

On the Tree-Level S-Matrix of Yang-Mills Theory

In this note we further investigate the procedure for computing tree-level amplitudes in Yang-Mills theory from connected instantons in the B-model on P^{3|4}, emphasizing that the problem of calculating Feynman diagrams is recast into the problem of finding solutions to a certain set of algebraic equations. We show that the B-model correctly reproduces all 6-particle amplitudes, including non-MHV amplitudes with three negative and three positive helicity gluons. As a further check, we also show that n-particle amplitudes obtained from the B-model obey a number of properties required of gauge theory, such as parity symmetry (which relates an integral over degree d curves to one over degree n-d-2 curves) and the soft and collinear gluon poles.

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