Gauge Theory, Geometry and the Large N Limit

We study the relationship between M theory on a nearly lightlike circle and U(N) gauge theory in p+1 dimensions. We define large N limits of these theories in which low energy supergravity is valid. The regularity of these limits implies an infinite series of nonrenormalization theorems for the gauge theory effective action, and the leading large N terms sum to a Born-Infeld form. Compatibility of two different large N limits that describe the same decompactified M theory leads to a conjecture for a relation between two limits of string theories.Comment: LaTeX, 17 pages, 1 figure, references added, shorter version to appear in Nucl. Phys.

Anomalies and large N limits in matrix string theory

We study the loop expansion for the low energy effective action for matrix string theory. For long string configurations we find the result depends on the ordering of limits. Taking $g_s\to 0$ before $N\to\infty$ we find free strings. Reversing the order of limits however we find anomalous contributions coming from the large $N$ limit that invalidate the loop expansion. We then embed the classical instanton solution into a long string configuration. We find the instanton has a loop expansion weighted by fractional powers of $N$. Finally we identify the scaling regime for which interacting long string configurations have a well defined large $N$ limit. The limit corresponds to large "classical" strings and can be identified with the "dual of the 't Hooft limit, $g_{SYM}^2\sim N$.Comment: 13 pages, 1 figure, harvmac.tex, notational errors corrected, references added. Trivial error in section 5 corrected with the result that the domain of validity of the loop expn. is slightly modifie

Three-graviton scattering in Matrix theory revisited

We consider a subset of the terms in the effective potential describing three-graviton interactions in Matrix theory and in classical eleven-dimensional supergravity. In agreement with the results of Dine and Rajaraman, we find that these terms vanish in Matrix theory. We show that the absence of these terms is compatible with the classical supergravity theory when the theory is compactified in a lightlike direction, resolving an apparent discrepancy between the two theories. A brief discussion is given of how this calculation might be generalized to compare the Matrix theory and supergravity descriptions of an arbitrary 3-body system.Comment: 9 pages, LaTeX; v2: reference added, v3: text unchanged, Note added clarifying connection with other recent result

Unitary matrix model for toroidal compactifications of M theory

A unitary matrix model is proposed as the large-N matrix formulation of M theory on flat space with toroidal topology. The model reproduces the motion of elementary D-particles on the compact space, and admits membrane states with nonzero wrapping around nontrivial 2-tori even at finite N.Comment: 8 pages, phyzzx. Version to appear in Phys. Lett. B; contains an additional discussion on the motivation for the model and extra reference

On the Geometry of the String Landscape and the Swampland

We make a number of conjectures about the geometry of continuous moduli parameterizing the string landscape. In particular we conjecture that such moduli are always given by expectation value of scalar fields and that moduli spaces with finite non-zero diameter belong to the swampland. We also conjecture that points at infinity in a moduli space correspond to points where an infinite tower of massless states appear, and that near these regions the moduli space is negatively curved. We also propose that there is no non-trivial 1-cycle of minimum length in the moduli space. This leads in particular to the prediction of the existence of a radially massive partner to the axion. These conjectures put strong constraints on inflaton potentials that can appear in a consistent quantum theory of gravity. Our conjectures are supported by a number of highly non-trivial examples from string theory. Moreover it is shown that these conditions can be violated if gravity is decoupled.Comment: 18 page

Conservation of Supergravity Currents from Matrix Theory

In recent work by Kabat and Taylor, certain Matrix theory quantities have been identified with the spatial moments of the supergravity stress-energy tensor, membrane current, and fivebrane current. In this note, we determine the relations between these moments required by current conservation, and prove that these relations hold as exact Matrix Theory identities at finite N. This establishes conservation of the effective supergravity currents (averaged over the compact circle). In addition, the constraints of current conservation allow us to deduce Matrix theory quantities corresponding to moments of the spatial current of the longitudinal fivebrane charge, not previously identified.Comment: 11 pages, LaTeX, typos correcte

An examination of the factors that influence the publication or non-publication of mental health nursing research presented at national or international nursing conferences

Mental health nurses are required to be able to identify and access the current evidence surrounding a particular topic and evaluate and decide upon the best care approach to people with mental health problems. This is aided by specific guidance on how to facilitate access to and deliver the best quality evidence-based care. This is most commonly acquired by accessing evidence through hand searching publications or through electronic sources (databases, web search engines or internet publications). However, evidence indicates that only a small proportion of mental health nursing research is published and that many nurses carry out research that is not published. Although, it is difficult to judge the quality of unpublished research the likelihood is that a number of high quality mental health nursing research projects are not published and are therefore not available to be evaluated as part of the evidence base of care. There has been relatively little examination of the reasons underpinning publication of nursing research. This project examined the factors that influence the publication or non-publication of mental health nursing research presented at national or international nursing conferences in the UK

D-branes and Matrix Theory in Curved Space

We discuss the relation between supersymmetric gauge theory of branes and supergravity; as it was discovered in D-brane physics, and as it appears in Matrix theory, with emphasis on motion in curved backgrounds. We argue that gauged sigma model Lagrangians can be used as definitions of Matrix theory in curved space. Lecture given at Strings '97; June 20, 1997.Comment: LaTeX with espcrc2; 13 pages, STRINGS97. References added; a speculation refute

A Matrix Model for Heterotic Spin(32)/Z2Spin(32)/Z_2 and Type I String Theory

We consider Heterotic string theories in the DLCQ. We derive that the matrix model of the Spin(32)/$Z_2$ Heterotic theory is the theory living on N D-strings in type I wound on a circle with no Spin(32)/$Z_2$ Wilson line on the circle. This is an O(N) gauge theory. We rederive the matrix model for the \e8 Heterotic string theory, explicitly taking care of the Wilson line around the lightlike circle. The result is the same theory as for Spin(32)/$Z_2$ except that now there is a Wilson line on the circle. We also see that the integer N labeling the sector of the O(N) matrix model is not just the momentum around the lightlike circle, but a shifted momentum depending on the Wilson line. We discuss the aspect of level matching, GSO projections and why, from the point of view of matrix theory the \e8 theory, and not the Spin(32)/$Z_2$, develops an 11'th dimension for strong coupling. Furthermore a matrix theory for type I is derived. This is again the O(N) theory living on the D-strings of type I. For small type I coupling the system is 0+1 dimensional quantum mechanics.Comment: 11pp harvmac Te

D-instantons probing D3-branes and the AdS/CFT correspondence

D-instantons are considered as a probe of coinciding $N$ D3-branes. They can feel an external metric via the commutator terms in their effective action. We show that when the D-instantons are separated from the D3-branes, the metric which is probed at the one loop level, {\it exactly} coincides with that of the BPS R-R 3-brane. Interesting connection of this result to the possible explanation of the AdS/CFT correspondence within IKKT M-atrix theory is discussed.Comment: 8pp., Latex. Minor changes, misprints are correcte