arXiv subjects

I. L. Buchbinder

Publications and source records attributed to I. L. Buchbinder.

At least 181 records · Page 10Linked to original sources

arXiv2000

Equations of Motion for Massive Spin 2 Field Coupled to Gravity

We investigate the problems of consistency and causality for the equations of motion describing massive spin two field in external gravitational and massless scalar dilaton fields in arbitrary spacetime dimension. From the field theoretical point of view we consider a general classical action with non-minimal couplings and find gravitational and dilaton background on which this action describes a theory consistent with the flat space limit. In the case of pure gravitational background all field components propagate causally. We show also that the massive spin two field can be consistently described in arbitrary background by means of the lagrangian representing an infinite series in the inverse mass. Within string theory we obtain equations of motion for the massive spin two field coupled to gravity from the requirement of quantum Weyl invariance of the corresponding two dimensional sigma-model. In the lowest order in $α'$ we demonstrate that these effective equations of motion coincide with consistent equations derived in field theory.

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arXiv2000

Low-Energy Effective Action of N=2 Gauge Multiplet Induced by Hypermultiplet Matter

We study one-loop effective action of hypermultiplet theory coupled to external N=2 vector multiplet. We formulate this theory in N=1 superspace and develop a general approach to constructing derivative expansion of the effective action based on an operator symbol technique adopted to N=1 supersymmetric field models. The approach under consideration allows to investigate on a unique ground a general structure of effective action and obtain both N=2 superconformal invariant (non-holomorphic) corrections and anomaly (holomorphic) corrections. The leading low-energy contributions to effective action are found in explicit form.

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arXiv2000

Causality of Massive Spin 2 Field in External Gravity

We investigate the structure of equations of motion and lagrangian constraints in a general theory of massive spin 2 field interacting with external gravity. We demonstrate how consistency with the flat limit can be achieved in a number of specific spacetimes. One such example is an arbitrary static spacetime though equations of motion in this case may lack causal properties. Another example is provided by external gravity fulfilling vacuum Einstein equations with arbitrary cosmological constant. In the latter case there exists one-parameter family of theories describing causal propagation of the correct number of degrees of freedom for the massive spin 2 field in arbitrary dimension. For a specific value of the parameter a gauge invariance with a vector parameter appears, this value is interpreted as massless limit of the theory. Another specific value of the parameter produces gauge invariance with a scalar parameter and this cannot be interpreted as a consistent massive or massless theory.

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arXiv2000

Low-Energy Effective Action in N=4 Super Yang-Mills Theories

We review a recent progress in constructing low-energy effective action in N=4 super Yang-Mills theories. Using harmonic superspace approach we consider N=4 SYM in terms of unconstrained N=2 superfield and apply N=2 background field method to finding effective action for N=4 SU(n) SYM broken down to U(n)$^{n-1}$. General structure of leading low-energy corrections to effective action is discussed.

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arXiv2000

N=4 Super Yang-Mills Low-Energy Effective Action at Three and Four Loops

We investigate the low-energy effective action in N=4 super Yang-Mills theory with gauge group SU(n) spontaneously broken down to its maximal torus. Using harmonic superspace technique we prove an absence of any three- and four-loop corrections to non-holomorphic effective potential depending on N=2 superfield strengths. A mechanism responsible for vanishing arbitrary loop corrections to low-energy effective action is discussed.

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arXiv2000

Structure of Low-Energy Effective Action in N=4 Supersymmetric Yang-Mills Theories

We study a problem of low-energy effective action in N=4 super Yang-Mills theories. Using harmonic superspace approach we consider N=4 SYM in terms of unconstrained N=2 superfield and apply N=2 background field method to finding effective action for N=4 SU(n) SYM broken down to U(n)$^{n-1}$. General structure of leading low-energy corrections to effective action is discussed and calculational procedure for their explicit finding is presented.

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arXiv1999

On Low-Energy Effective Actions in N = 2, 4 Superconformal Theories in Four Dimensions

We study some aspects of low-energy effective actions in 4-d superconformal gauge theories on the Coulomb branch. We describe superconformal invariants constructed in terms of N=2 abelian vector multiplet which play the role of building blocks for the N=2,4 supersymmetric low-energy effective actions. We compute the one-loop effective actions in constant N=2 field strength background in N=4 SYM theory and in N=2 SU(2) SYM theory with four hypermultiplets in fundamental representation. Using the classification of superconformal invariants we then find the manifestly N=2 superconformal form of these effective actions. While our explicit computations are done in the one-loop approximation, our conclusions about the structure of the effective actions in N=2 superconformal theories are general. We comment on some applications to supergravity - gauge theory duality in the description of D-brane interactions.

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arXiv1999

One-loop effective potential of N=1 supersymmetric theory and decoupling effects

We study the decoupling effects in N=1 (global) supersymmetric theories with chiral superfields at the one-loop level. The examples of gauge neutral chiral superfields with the minimal (renormalizable) as well as non-minimal (non- renormalizable) couplings are considered, and decoupling in gauge theories with U(1) gauge superfields that couple to heavy chiral matter is studied. We calculate the one-loop corrected effective Lagrangians that involve light fields and heavy fields with mass of order M. The elimination of heavy fields by equations of motion leads to decoupling effects with terms that grow logarithmically with M. These corrections renormalize light fields and couplings in the theory (in accordance with the "decoupling theorem"). When the field theory is an effective theory of the underlying fundamental theory, like superstring theory, where the couplings are calculable, such decoupling effects modify the low-energy predictions for the effective couplings of light fields. In particular, for the class of string vacua with an "anomalous" U(1) the vacuum restabilization triggers the decoupling effects, which can significantly modify the low energy predictions for the couplings of the surviving light fields. We also demonstrate that quantum corrections to the chiral potential depending on massive background superfields and corresponding to supergraphs with internal massless lines and external massive lines can also arise at the two-loop level.

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arXiv1999

On Holomorphic Effective Actions of Hypermultiplets Coupled to External Gauge Superfields

We study the structure of holomorphic effective action for hypermultiplet models interacting with background super Yang-Mills fields. A general form of holomorphic effective action is found for hypermultiplet belonging to arbitrary representation of any semisimple compact Lie group spontaneously broken to its maximal abelian subgroup. The applications of obtained results to hypermultiplets in fundamental and adjoint representations of the SU(n), SO(n), Sp(n) groups are considered.

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arXiv1999

On Consistent Equations for Massive Spin-2 Field Coupled to Gravity in String Theory

We investigate the problem of derivation of consistent equations of motion for the massive spin 2 field interacting with gravity within both field theory and string theory. In field theory we derive the most general classical action with non-minimal couplings in arbitrary spacetime dimension, find the most general gravitational background on which this action describes a consistent theory and generalize the analysis for the coupling with background scalar dilaton field. We show also that massive spin 2 field allows in principle consistent description in arbitrary background if one builds its action in the form of an infinite series in the inverse mass square. Using sigma-model description of string theory in background fields we obtain in the lowest order in $α'$ the explicit form of effective equations of motion for the massive spin 2 field interacting with gravity from the requirement of quantum Weyl invariance and demonstrate that they coincide with the general form of consistent equations derived in field theory.

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arXiv1999

Holomorphic effective potential in general chiral superfield model

We study a holomorphic effective potential $W_{eff}(Φ)$ in chiral superfield model defined in terms of arbitrary kählerian potential $K(\barΦ,Φ)$ and arbitrary chiral potential $W(Φ)$. Such a model naturally arises as an ingredient of low-energy limit of superstring theory and it is called here the general chiral superfield model. Generic procedure for calculating the chiral loop corrections to effective action is developed. We find lower two-loop correction in the form $W^{(2)}_{eff}(Φ)= 6/(4π)^4 \bar{W}^{'''2}(0){(\frac{W^{''}(Φ)}{K^2_{Φ\barΦ(0,Φ)}})}^3$ where $K_{Φ\barΦ}(0,Φ)=\frac{\partial^2 K(\barΦ,Φ)} {\partialΦ\partial\barΦ}|_{\barΦ=0}$ and $ζ(x)$ be Riemannian zeta-function. This correction is finite at any $K(\barΦ,Φ), W(Φ)$.

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arXiv1999

Implications of decoupling effects for one-loop corrected effective actions from superstring theory

We study the decoupling effects in one-loop corrected N=1 supersymmetric theory with gauge neutral chiral superfields, by calculating the one-loop corrected effective Lagrangian that involves light and heavy fields with the mass scale M, and subsequently eliminating heavy fields by their equations of motion. In addition to new non-renormalizable couplings, we determine the terms that grow as log(M) and renormalize the fields and couplings in the effective field theory, in accordance with the decoupling theorem. However, in a theory derived from superstring theory, these terms can significantly modify low energy predictions for the effective couplings of light fields. For example, in a class of heterotic superstring vacua with an anomalous U(1) the vacuum restabilization introduces such decoupling effects which in turn correct the low energy predictions for certain couplings by 10-50%.

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arXiv1999

Low-Energy Effective Action in N=4 Super Yang-Mills Theory

We consider N=4 supersymmetric Yang-Mills theory formulated in terms of N=2 superfields in harmonic superspace. Using the background field method we define manifestly gauge invariant and N=2 supersymmetric effective action depending on N=2 strength superfields and develop a general procedure for its calculation in one-loop approximation. Explicit form for this effective action is found for the case of SU(2) gauge group broken down to U(1).

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arXiv1998

Non-holomorphic effective potential in N = 4 SU(n) SYM

We compute the one-loop non-holomorphic effective potential for the N=4 SU(n) supersymmetric Yang-Mills theory with the gauge symmetry broken down to the maximal torus. Our approach remains powerful for arbitrary gauge groups and is based on the use of N=2 harmonic superspace formulation for general N=2 Yang-Mills theories along with the superfield background field method.

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arXiv1998

Comments on the Background Field Method in Harmonic Superspace: Non-holomorphic Corrections in N=4 SYM

We analyse the one-loop effective action of N=4 SYM theory in the framework of the background field formalism in N=2 harmonic superspace. For the case of on-shell background N=2 vector multiplet we prove that the effective action is free of harmonic singularities. When the lowest N=1 superspace component of the N=2 vector multiplet is switched off, the effective action of N=4 SYM theory is shown to coincide with that obtained by Grisaru et al on the base of the N=1 background field method. We compute the leading non-holomorphic corrections to the N=4 SU(2) SYM effective action.

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arXiv1998

Central Charge as the Origin of Holomorphic Effective Action in N=2 Gauge Theory

We explicitly demonstrate that the perturbative holomorphic contribution to the off-shell effective action of N=2 U(1) gauge supermultiplet is an entire effect of the minimal coupling to a hypermultiplet with the mass generated by a central charge in N=2 superalgebra. The central charge is induced by a constant vacuum N=2 gauge superfield strength spontaneously breaking the automorphism U(1)_R symmetry of N=2 superalgebra. We use the manifestly off-shell supersymmetric harmonic superspace techniques of quantum calculations with the central charge-massive hypermultiplet propagator.

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arXiv1998

Effective Action of N=2 Supersymmetric Field Theories in Harmonic Superspace Approach

The paper is a brief review of the works devoted to problem of effective action in N=2 super Yang-Mills theories in harmonic superspace approach. The formulation of N=2 superfield models in harmonic superspace is discussed, background field method for N=2 super Yang-Mills theory is constructed and general structure of effective action in harmonic superspace is investigated. It is shown how the holomorphic and non-holomorphic contributions to effective action can be calculated within the harmonic superspace approach.

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arXiv1998

Background Field Method and Structure of Effective Action in N=2 Super Yang-Mills Theories

This paper is a brief review of background field method and some of its applications in N=2 super Yang-Mills theories with a matter within harmonic superspace approach. A general structure of effective action is discussed, an absence of two-loop quantum corrections to first non-leading term in effective action is proved and N=2 non-renormalization theorem in this approach is considered.

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