M5-branes and Matrix Theory

We consider supermembranes ending on M5-branes, with the aim of deriving the appropriate matrix theories describing different situations. Special attention is given to the case of non-vanishing (selfdual) C-field. We identify the relevant deformation of the six-dimensional super-Yang-Mills theory whose dimensional reduction is the matrix theory for membranes in the presence of M5-branes. Possible applications and limitations of the models are discussed.Comment: 10 pp., plain tex. Contribution to the proceedings of the International Workshop "Supersymmetries and Quantum Symmetries" (SQS'03, Dubna, Russia, July 24-29, 2003) and of the 9th Adriatic Meeting "Particle Physics and the Universe" (Dubrovnik, Croatia, September 4-14, 2003

Biotransport of Organic Pollutants to an Inland Alaska Lake by Migrating Sockeye Salmon (Oncorhynchus nerka)

Persistent organic pollutants such as polychlorinated biphenyls (PCBs) and the pesticide DDT, known to harm wildlife, have been shown to reach pristine Subarctic and Arctic areas by global atmospheric transport. Another transport route for pollutant entry into these ecosystems is provided by migrating salmon. Pollutant transport was studied in a population of sockeye salmon (Oncorhynchus nerka) in the Copper River, Alaska during their 410 km spawning mighration. Pollutants accumulated by the salmon during their ocean life stage were not eliminated during migration, but were transported to the spawning lakes and accumulated in the freshwater food web there. The influence of the biotransported pollutants was investigated by comparing pollutant levels and compositions in atmospheric deposition as well in two different populations of arctic grayling (Thymallus arcticus). One grayling population was in the salmon spawning lake and the other in a nearby lake not hosting anadromous fish, but receiving pollutants only via atmospheric deposition. The grayling in the salmon spawning lake were found to have concentrations of organic pollutants more than two times higher than those of the grayling in the salmon-free lake, and the pollutant composition resembled that found in salmon. Thus, in the studied Alaska river system, biotransport was found to have a far greater influence than atmospheric input on the PCB and DDT levels in lake biota.Il a été prouvé que des polluants organiques persistants comme les diphényles polychlorés (PCB) et le pesticide D.D.T., dont on connaît les répercussions néfastes sur la faune, se répandent dans des zones subarctiques et arctiques vierges par le biais du transport atmosphérique global. Les saumons en migration offrent une autre voie de transport pour l'entrée des polluants dans ces écosystèmes. On a étudié le transport des polluants dans une population de saumon sockeye (Oncorhynchus nerka) remontant le fleuve Copper, en Alaska, durant la migration de frai de 410 km. Les polluants accumulés par le saumon au cours de sa vie océanique n'étaient pas éliminés durant la migration, mais étaient transportés dans les frayères des lacs où ils s'accumulaient dans le réseau trophique de l'eau douce. On a étudié l'influence des polluants bio-transportés en comparant les niveaux et les compositions de polluants dans les retombées atmosphériques ainsi que dans deux populations distinctes d'ombre arctique (Thymallus arcticus). Une des populations d'ombre se trouvait dans le lac où frayaient les saumons et l'autre dans un lac voisin, ne contenant pas de poissons anadromes, mais recevant des polluants uniquement par retombées atmosphériques. On a trouvé que l'ombre qui se trouvait dans le lac où frayaient les saumons avait des concentrations en polluants organiques deux fois plus grandes que l'ombre qui se trouvait dans le lac sans saumons, et la composition des polluants ressemblait à celle que l'on retrouvait dans le saumon. Ainsi, dans le réseau fluvial de l'Alaska qui faisait l'objet de cette étude, on a trouvé que le transport biologique avait une influence beaucoup plus importante que les retombées atmosphériques sur les niveaux de PCB et de D.D.T. dans le biote lacustre

A Study of Holographic Renormalization Group Flows in d=6 and d=3

We present an explicit study of the holographic renormalization group (RG) in six dimensions using minimal gauged supergravity. By perturbing the theory with the addition of a relevant operator of dimension four one flows to a non-supersymmetric conformal fixed point. There are also solutions describing non-conformal vacua of the same theory obtained by giving an expectation value to the operator. One such vacuum is supersymmetric and is obtained by using the true superpotential of the theory. We discuss the physical acceptability of these vacua by applying the criteria recently given by Gubser for the four dimensional case and find that those criteria give a clear physical picture in the six dimensional case as well. We use this example to comment on the role of the Hamilton-Jacobi equations in implementing the RG. We conclude with some remarks on AdS_4 and the status of three dimensional superconformal theories from squashed solutions of M-theory.Comment: 15 pages, 5 figures, V2: minor change

Fostering Automatic Control Students to Become Innovators

Today, innovation is a key word for many universities, as it constitutes an important part of most universities’ public and scientific outreach task. Many universities are striving to increase the number of innovations generated at the university. A common method is to provide various support for research projects e.g.; providing researchers with information about international patent rights (IPR), offering administrative or financial help concerning patent applications, giving entrepreneurship and start-up support, etc. However, fostering innovators and entrepreneurs can start already in undergraduate/graduate courses, i.e. long before a student potentially reaches the research level. We believe that key factors for success in this matter are diversity and freedom. A course that strives to promote innovation capability must allow for students with different backgrounds and different curricula to meet and work together, and must allow for students to freely use their current knowledge within new contexts. This is generally not a setting provided in traditional undergraduate/graduate courses. This article describes the execution and outcome of an graduate course “international Market-Driven Engineering (iMDE)” in which diversity and freedom are key factors. The course is international and multi-disciplinary in terms of students, teachers and subjects. Graduate students with prior knowledge in automatic control constitute one important part of the course population. We believe that the diversity amongst the students, and their freedom when it comes to both innovation process and product, provides a promising platform in which seeds of ideas can grow into conceptual prototypes that build a solid foundation for full-scale innovations. On of the iMDE- projects, the Elderly Accessible Chair, or EA Chair, with its automated scanning and automatic seat- provider functionality, is one concrete example of this

Holographic Noncommutativity

We examine noncommutative Yang-Mills and open string theories using magnetically and electrically deformed supergravity duals. The duals are near horizon regions of Dp-brane bound state solutions which are obtained by using O(p+1,p+1) transformations of Dp-branes. The action of the T-duality group implies that the noncommutativity parameter is constant along holographic RG-flows. The moduli of the noncommutative theory, i.e., the open string metric and coupling constant, as well as the zero-force condition are shown to be invariant under the O(p+1,p+1) transformation, i.e., deformation independent. We find sufficient conditions, including zero force and constant dilaton in the ISO(3,1)-invariant D3 brane solution, for exact S-duality between noncommutative Yang-Mills and open string theories. These results are used to construct noncommutative field and string theories with N=1 supersymmetry from the T^(1,1) and Pilch-Warner solutions. The latter has a non-trivial zero-force condition due to the warping.Comment: latex, 40 pp. v2: minor changes, one ref. added. v3: corrections in eqs. 27 and 7

An M-theory solution generating technique and SL(2,R)

In this paper we generalize the O(p+1,p+1) solution generating technique (this is a method used to deform Dp-branes by turning on a NS-NS B-field) to M-theory, in order to be able to deform M5-brane supergravity solutions directly in eleven dimensions, by turning on a non zero three form A. We find that deforming the M5-brane, in some cases, corresponds to performing certain SL(2,R) transformations of the Kahler structure parameter for the three-torus, on which the M5-brane has been compactified. We show that this new M-theory solution generating technique can be reduced to the O(p+1,p+1) solution generating technique with p=4. Further, we find that it implies that the open membrane metric and generalized noncommutativity parameter are manifestly deformation independent for electric and light-like deformations. We also generalize the O(p+1,p+1) method to the type IIA/B NS5-brane in order to be able to deform NS5-branes with RR three and two forms, respectively. In the type IIA case we use the newly obtained solution generating technique and deformation independence to derive a covariant expression for an open D2-brane coupling, relevant for OD2-theory.Comment: 24 pages, Latex. v2:Sections 3.2 and 3.3 improved. v3:Some clarifications added. Version published in JHE

U-duality covariant membranes

We outline a formulation of membrane dynamics in D=8 which is fully covariant under the U-duality group SL(2,Z) x SL(3,Z), and encodes all interactions to fields in the eight-dimensional supergravity, which is constructed through Kaluza-Klein reduction on T^3. Among the membrane degrees of freedom is an SL(2,R) doublet of world-volume 2-form potentials, whose quantised electric fluxes determine the membrane charges, and are conjectured to provide an interpretation of the variables occurring in the minimal representation of E_{6(6)} which appears in the context of automorphic membranes. We solve the relevant equations for the action for a restricted class of supergravity backgrounds. Some comments are made on supersymmetry and lower dimensions.Comment: LaTeX, 21 pages. v2: Minor changes in text, correction of a sign. v3: some changes in text, a sign convention changed; version to appear in JHE

Deformation independent open brane metrics and generalized theta parameters

We investigate the consequences of generalizing certain well established properties of the open string metric to the conjectured open membrane and open Dp-brane metrics. By imposing deformation independence on these metrics their functional dependence on the background fields can be determined including the notorious conformal factor. In analogy with the non-commutativity parameter $\Theta^{\mu\nu}$ in the string case, we also obtain `generalized' theta parameters which are rank q+1 antisymmetric tensors (polyvectors) for open Dq-branes and rank 3 for the open membrane case. The expressions we obtain for the open membrane quantities are expected to be valid for general background field configurations, while the open D-brane quantities are only valid for one parameter deformations. By reducing the open membrane data to five dimensions, we show that they, modulo a subtlety with implications for the relation between OM-theory and NCYM, correctly generate the open string and open D2-data.Comment: 24 pages, LaTe

Light-like noncommutativity and duality from open strings/branes

In this paper we perform some non-trivial tests for the recently obtained open membrane/D-brane metrics and `generalized' noncommutativity parameters using Dp/NS5/M5-branes which have been deformed by light-like fields. The results obtained give further evidence that these open membrane/D-brane metrics and `generalized' noncommutativity parameters are correct. Further, we use the open brane data and supergravity duals to obtain more information about non-gravitational theories with light-like noncommutativity, or `generalized' light-like noncommutativity. In particular, we investigate various duality relations (strong coupling limits). In the light-like case we also comment on the relation between open membrane data (open membrane metric etc.) in six dimensions and open string data in five dimensions. Finally, we investigate the strong coupling limit (high energy limit) of five dimensional NCYM with \Theta^{12}=\Theta^{34}. In particular, we find that this NCYM theory can be UV completed by a DLCQ compactification of M-theory.Comment: 24 pages, Latex. v2:Comments and references added. v3:Version published in JHE