Effects of D-instantons

Scattering of fundamental states of type IIB supergravity and superstring theory is discussed at low orders in perturbation theory in the background of a D-instanton. The integration over fermionic zero modes in both the low energy supergravity and in the string theory leads to explicit nonperturbative terms in the effective action. These include a single instanton correction to the known tree-level and one-loop $R^4$ interactions. The `spectrum' of multiply-charged D-instantons is deduced by T-duality in nine dimensions from multiply-wound world-lines of marginally-bound D-particles. This, and other clues, lead to a conjectured SL(2,Z) completion of the $R^4$ terms which suggests that they are not renormalized by perturbative corrections in the zero-instanton sector beyond one loop. The string theory unit-charged D-instanton gives rise to point-like effects in fixed-angle scattering, raising unresolved issues concerning distance scales in superstring theory.Comment: 31 pages, 6 figures, Latex, Reference added, corrected coefficients in expansion of generalized Eisenstein series in equation 66 now agree with hep-th/970414

Four-quark flux distribution and binding in lattice SU(2)

The full spatial distribution of the color fields of two and four static quarks is measured in lattice SU(2) field theory at separations up to 1 fm at beta=2.4. The four-quark case is equivalent to a qbar q qbar q system in SU(2) and is relevant to meson-meson interactions. By subtracting two-body flux tubes from the four-quark distribution we isolate the flux contribution connected with the four-body binding energy. This contribution is further studied using a model for the binding energies. Lattice sum rules for two and four quarks are used to verify the results.Comment: 46 pages including 71 eps figures. 3D color figures are available at www.physics.helsinki.fi/~ppennane/pics

A Curious Truncation of N=4 Yang-Mills

The coupling constant dependence of correlation functions of BPS operators in N=4 Yang-Mills can be expressed in terms of integrated correlation functions. We approximate these integrated correlators by using a truncated OPE expansion. This leads to differential equations for the coupling dependence. When applied to a particular sixteen point correlator, the coupling dependence we find agrees with the corresponding amplitude computed via the AdS/CFT correspondence. We conjecture that this truncation becomes exact in the large N and large 't Hooft coupling limit.Comment: 10 pages, LaTeX; additional comments, added reference

A Confirmatory Factor Analysis of Two Web Site Usability Instruments

Many perspectives of user acceptance of Web sites have been examined, yet information systems research often overlooks the human-computer interaction aspects, particularly in the area of Web site usability. Web site usability has recently gained greater acceptance in information literature through the development of instruments by Palmer (2002) and Agarwal and Venkatesh (2002). This study conducted a confirmatory factor analysis of both instruments in an attempt to validate the two instruments. Our results found that the Palmer instrument exhibited satisfactory measurement properties, although allowing room for further refinement. The Agarwal and Venkatesh instrument, although useful as a practical metric, displayed poor validity for the underlying constructs that compose Web site usability. Validation of these instruments furthers their scope and potential use by researchers and practitioners in helping them better understand the capabilities of their Web sites, while providing a foundation for further refinement of the Web site usability construct

Can NFL Players Obtain Judicial Review of Arbitration Decisions on the Merits when a Typical Hourly Union Worker Cannot Obtain This Unusual Court Access?

Several recent court cases, brought on behalf of National Football League (NFL) players by their union, the NFL Players Association (NFLPA), have increased media and public attention to the challenges of labor arbitrator decisions in federal courts. The Supreme Court has established a body of federal common law that places a high premium on deferring to labor arbitrator decisions and counseling against judges deciding the merits of disputes covered by a collective bargaining agreement (CBA). A recent trend suggests federal judges have ignored this body of law and analyzed the merits of labor arbitration decisions in the NFL setting. NFL employees, as millionaires, are able to use a significant war chest, given to their union, to hire very prominent attorneys to argue their cases in federal courts after the union has lost the dispute in final and binding arbitration. Unlike a typical hourly union worker, who has very limited legal options after an arbitration award has been rendered, millionaire professional football players and their union appear to be successfully challenging labor arbitrator decisions on the merits in federal district courts. Their prominent attorneys, from major corporate law firms that tend to represent employers in workplace disputes, appear to add value in resources and skills on behalf of their rich, professional football employee clients. Do these rich financial and legal resources suggest an unusual access to judges who may be more willing to hear their novel legal arguments outside of the typical standards established by the Supreme Court’s federal arbitration jurisprudence? This Article explores the recent access to court that NFL players have been able to obtain in challenging decisions made pursuant to a CBA. The Article argues that the financial resources of these unique union employees have led to the unusual access and consideration by federal trial judges in reviewing the merits of decisions that typically would not be considered under federal labor arbitration law. Overall, however, the record also suggests that the immediate appellate courts have responded to overturn this unusual consideration of the merits of labor arbitration decisions by reversing those initial court opinions. This Article concludes that, because of the strong public interest in labor arbitration decisions involving the NFLPA, the federal courts must normally defer to the arbitrator’s decision regardless of the merits. Otherwise, a typical union worker challenging a labor arbitrator’s decision will be left with the wrong perception about access to justice and believe that one must be rich to have a federal judge consider the merits of a labor dispute

The Relationship between Cost Analysis and Program Management

Cost analysis if often viewed as applying basic principles and cost methodologies to determine total system cost. These finished estimates then flow into a decision making process and the cost estimator leaves the stage. Reality shows that the cost estimator is actually one of the main contributors to the decision making process. Our introduction to this special issue explores the areas where cost estimating plays a major role in program management in areas beyond the normal program estimate. We have included articles that show the key role estimators can play in source selection strategies and evaluation; cost of delay analysis for management decisions, earned value management methods to predict program costs; decision criteria to rank competing projects that complement traditional cost-based methods; and a new methodology for determining research and development budget profiles

Preliminary results of the heavy-light meson spectrum using chirally improved light quarks

Using a ``wall'' of quark point sources, we invert the chirally improved Dirac operator to create an ``incoherent'' collection of quark propagators which originate from all spatial points of the source time slice. The lowest-order NRQCD approximation is used to create heavy-quark propagators from the same wall source. However, since the numerical cost involved in computing such heavy-quark propagators is low, we are able to use a number of source gauge paths to establish coherence between the heavy and light quarks at several spatial separations. The resulting collection of heavy-light meson correlators is analyzed to extract the corresponding mass spectrum.Comment: 3 pages, 1 figure, Lattice2004(spectrum), minor corrections adde

Quantum Moduli Spaces of N=1N=1 String Theories

Generically, string models with $N=1$ supersymmetry are not expected to have moduli beyond perturbation theory; stringy non-perturbative effects as well as low energy field-theoretic phenomena such as gluino condensation will lift any flat directions. In this note, we describe models where some subspace of the moduli space survives non-perturbatively. Discrete $R$ symmetries forbid any inherently stringy effects, and dynamical considerations control the field-theoretic effects. The surviving subspace is a space of high symmetry; the system is attracted to this subspace by a potential which we compute. Models of this type may be useful for considerations of duality and raise troubling cosmological questions about string theory. Our considerations also suggest a mechanism for fixing the expectation value of the dilaton.Comment: 26 pages; uses harvmac. Footnote re fixing dilaton adde

Duality and higher derivative terms in M theory

Dualities of M-theory are used to determine the exact dependence on the coupling constant of the D^6R^4 interaction of the IIA and IIB superstring effective action. Upon lifting to eleven dimensions this determines the coefficient of the D^6R^4 interaction in eleven-dimensional M-theory. These results are obtained by considering the four-graviton two-loop scattering amplitude in eleven-dimensional supergravity compactified on a circle and on a two-torus -- extending earlier results concerning lower-derivative interactions. The torus compactification leads to an interesting SL(2,Z)-invariant function of the complex structure of the torus (the IIB string coupling) that satisfies a Laplace equation with a source term on the fundamental domain of moduli space. The structure of this equation is in accord with general supersymmetry considerations and immediately determines tree-level and one-loop contributions to D^6R^4 in perturbative IIB string theory that agree with explicit string calculations, and two-loop and three-loop contributions that have yet to be obtained in string theory. The complete solution of the Laplace equation contains infinite series' of single D-instanton and double D-instanton contributions, in addition to the perturbative terms. General considerations of the higher loop diagrams of eleven-dimensional supergravity suggest extensions of these results to interactions of higher order in the low energy expansion.Comment: harvmac. 41 pages. 3 figures. v2 typos corrected and reference list updated. v3. Significant new subsection deriving the non-zero coefficient of the IIB string theory three-loop contributio

D-instanton partition functions

Duality arguments are used to determine D-instanton contributions to certain effective interaction terms of type II supergravity theories in various dimensions. This leads to exact expressions for the partition functions of the finite N D-instanton matrix model in d=4 and 6 dimensions that generalize our previous expression for the case d=10. These results are consistent with the fact that the Witten index of the T-dual D-particle process should only be non-vanishing for d=10.Comment: 20 pages, harvmac, typos corrected, reference adde