arXiv subjects

I. N. McArthur

Publications and source records attributed to I. N. McArthur.

25 records · Page 2Linked to original sources

arXiv2001

Hypermultiplet effective action: N = 2 superspace approach

In an earlier paper (hep-th/0101127), we developed heat kernel techniques in N = 2 harmonic superspace for the calculation of the low-energy effective action of N = 4 SYM theory, which can be considered as the most symmetric N = 2 SYM theory. Here, the results are extended to generic N = 2 SYM theories. This involves a prescription for computing the variation of the hypermultiplet effective action. Integrability of this variation allows the hypermultiplet effective action to be deduced. This prescription permits a very simple superfield derivation of the perturbative holomorphic prepotential. Explicit calculations of the prepotential and the leading non-holomorphic correction are presented.

hep-th↗

arXiv2001

Effective action of N = 4 super Yang-Mills: N = 2 superspace approach

Using the N = 2 off-shell formulation in harmonic superspace for N = 4 super Yang-Mills theory, we present a representation of the one-loop effective action which is free of so-called coinciding harmonic singularities and admits a straightforward evaluation of low-energy quantum corrections in the framework of an N = 2 superfield heat kernel technique. We illustrate our approach by computing the low-energy effective action on the Coulomb branch of SU(2) N = 4 super Yang-Mills. Our work provides the first derivation of the low-energy action of N = 4 super Yang-Mills theory directly in N = 2 superspace without any reduction to N = 1 superfields and for a generic background N = 2 Yang-Mills multiplet.

hep-th↗

arXiv1999

Kappa-Symmetry of Green-Schwarz Actions in Coset Superspaces

The nature of $κ$-symmmetry transformations is examined for p-branes embedded in a class of coset superspaces G/H, where G is an appropriate supergroup and H is the Lorentz subgroup. It is shown that one of the conditions $δZ^M E_M{}^a = 0$ which characterizes $κ$-symmetry transformations arises very naturally if they are implemented in terms of a right action of a subgroup of the supergroup G on the supergroup elements which represent the coset. Unlike the global left action of G on G/H (which gives rise to supersymmetry on the coset superspace), there is no canonically defined right action of G on G/H. However, an interpretation of this right action involving an enlargement of the isotropy group from the Lorentz subgroup to a subgroup of G with generators which include some of the fermionic generators of G is suggested. Closure of the generators of this larger subgroup under commutation leads to the usual `brane scan' for p-branes which have bosonic degrees of freedom which are worldvolume scalars.

hep-th↗

arXiv1998

Higher Order Spin-dependent Terms in D0-brane Scattering from the Matrix Model

The potential describing long-range interactions between D0-branes contains spin-dependent terms. In the matrix model, these should be reproduced by the one-loop effective action computed in the presence of a nontrivial fermionic background $ψ.$ The $\frac{v^3 ψ^2}{r^8}$ term in the effective action has been computed by Kraus and shown to correspond to a spin-orbit interaction between D0-branes, and the $\frac{ψ^8}{r^{11}}$ term in the static potential has been obtained by Barrio et al. In this paper, the $\frac{v^2 ψ^4}{r^9}$ term is computing in the matrix model and compared with the corresponding results of Morales et al obtained using string theoretic methods. The technique employed is adapted to the underlying supersymmetry of the matrix model, and should be useful in the calculation of spin-dependent effects in more general Dp-brane scatterings.

hep-th↗

arXiv1997

A ``Gaussian'' Approach to Computing Supersymmetric Effective Actions

For nonsupersymmetric theories, the one-loop effective action can be computed via zeta function regularization in terms of the functional trace of the heat kernel associated with the operator which appears in the quadratic part of the action. A method is developed for computing this functional trace by exploiting its similarity to a Gaussian integral. The procedure is extended to superspace, where it is used to compute the low energy effective action obtained by integrating out massive scalar supermultiplets in the presence of a supersymmetric Yang-Mills background.

hep-th↗

arXiv1995

Gauging of Nonlinearly Realized Symmetries

A representation of a subgroup H of a finite-dimensional group G can be used to induce a nonlinear realization of G. If the nonlinearly realized symmetry is gauged, then the BRST charge can be related by a similarity transformation to the BRST charge for the gauged linear realization of H (plus a cohomologically trivial piece). It is shown that the relation between the two BRST charges is a reflection of the fact that they can be interpreted geometrically as expressions for the exterior derivative on G relative to two different bases, and an explicit expression for the generator of the similarity transformation is obtained. This result is applied in an infinite-dimensional setting, where it yields the similarity transformation used by Ishikawa and Kato to prove the equivalence of the Berkovits-Vafa superstring with the underlying bosonic string theory.

hep-th↗

arXiv1994

The Berkovits-Vafa Construction and Nonlinear Realizations

Berkovits and Vafa recently showed that critical string theories can be considered as critical superstring theories with a special choice of background. The embedding of the Virasoro algebra into the super-Virasoro algebra involved in this construction has been extended to the noncritical case by Berkovits and Ohta. It is shown that the resulting nonlinear realization of the super-Virasoro algebra can be interpreted using standard techniques from the theory of nonlinear realizations. This extends earlier work of Kunitomo.

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