Leading Infrared Logarithms from Unitarity, Analyticity and Crossing

We derive non-linear recursion equations for the leading infrared logarithms in massless non-renormalizable effective field theories. The derivation is based solely on the requirements of the unitarity, analyticity and crossing symmetry of the amplitudes. That emphasizes the general nature of the corresponding equations. The derived equations allow one to compute leading infrared logarithms to essentially unlimited loop order without performing a loop calculation. For the implementation of the recursion equation one needs to calculate tree diagrams only. The application of the equation is demonstrated on several examples of effective field theories in four and higher space-time dimensions.Comment: 12 page

On Polyakov's basic variational formula for loop spaces

We use the homological algebra context to give a more rigorous proof of Polyakov's basic variational formula for loop spaces.Comment: Latex, 17 pages, no figure

On search for the M-Theory Lagrangian

We present a starting point for the search for a Lagrangian density for M-Theory using characteristic classes for flat foliations of bundles.Comment: Latex, 5 pages, no figure

Ultranarrow resonance in Coulomb drag between quantum wires at coinciding densities

We investigate the influence of the chemical potential mismatch $\Delta$ (different electron densities) on Coulomb drag between two parallel ballistic quantum wires. For pair collisions, the drag resistivity $\rho_{\rm D}(\Delta)$ shows a peculiar anomaly at $\Delta=0$ with $\rho_{\rm D}$ being finite at $\Delta=0$ and vanishing at any nonzero $\Delta$. The "bodyless" resonance in $\rho_{\rm D}(\Delta)$ at zero $\Delta$ is only broadened by processes of multi-particle scattering. We analyze Coulomb drag for finite $\Delta$ in the presence of both two- and three-particle scattering within the kinetic equation framework, focusing on a Fokker-Planck picture of the interaction-induced diffusion in momentum space of the double-wire system. We describe the dependence of $\rho_{\rm D}$ on $\Delta$ for both weak and strong intrawire equilibration due to three-particle scattering.Comment: 21 pages (+2.5 pages Suppl. Mat.), 2 figures; additional explanation

Induced (N,0) supergravity as a constrained Osp(N,2) WZWN model and its effective action

A chiral $(N,0)$ supergravity theory in d=2 dimensions for any $N$ and its induced action can be obtained by constraining the currents of an Osp(N$|$2) WZWN model. The underlying symmetry algebras are the nonlinear SO(N) superconformal algebras of Knizhnik and Bershadsky. The case $N=3$ is worked out in detail. We show that by adding quantum corrections to the classical transformation rules, the gauge algebra on gauge fields and currents closes. Integrability conditions on Ward identities are derived. The effective action is computed at one loop. It is finite, and can be obtained from the induced action by rescaling the central charge and fields by finite Z factors.Comment: 23

Magnetic Monopoles in Field Theory and Cosmology

The existence of magnetic monopoles is predicted by many theories of particle physics beyond the Standard Model. However, in spite of extensive searches, there is no experimental or observational sign of them. I review the role of magnetic monopoles in quantum field theory and discuss their implications for particle physics and cosmology. I also highlight their differences and similarities with monopoles found in frustrated magnetic systems, and discuss how experiments carried out in these systems could help us understand the physics of fundamental monopoles.Comment: 15 pages, no figures. Based on a talk given at the discussion meeting "Emergent magnetic monopoles in frustrated magnetic systems" at the Kavli Royal Society International Centre, 17-18 October 2011. To be published in Philosophical Transactions of the Royal Society

Evolution of Cosmic Necklaces and Lattices

Previously developed analytic models for the evolution of cosmic string and monopole networks are applied to networks of monopoles attached to two or more strings; the former case is usually known as cosmic necklaces. These networks are a common consequence of models with extra dimensions such as brane inflation. Our quantitative analysis agrees with (and extends) previous simpler estimates, but we will also highlight some differences. A linear scaling solution is usually the attractor solution for both the radiation and matter-dominated epochs, but other scaling laws can also exist, depending on the universe's expansion rate and the network's energy loss mechanisms.Comment: 4 page

Investigation of the soret effect in aqueous and non-aqueous mixtures by the thermal lens technique

In the present work we investigate the thermal diffusion behavior of three different binary mixtures with a thermal lens (TL) setup. In the setup used in this study we avoid the addition of a dye for systems, such as aqueous mixtures, with a weak absorption band at a wavelength of 980 nm. In some aqueous systems with a complex phase behavior the addition of dye significantly affects the apparent measured thermal diffusion properties. The studied systems are dimethylsulfoxide (DMSO) in water, the ionic liquid 1-ethyl-3-methylimidazolium ethylsulfate (EMIES) in butanol and a non-ionic surfactant hexaethylene glycol monododecyl ether (C(12)E(6)) in water. The Soret coefficients of the selected systems cover a range of two orders of magnitude. For DMSO in water with a very low Soret coefficient of the order of S(T) approximately 10(-3) K(-1) we find for a low DMSO content (c = 0.33) a reasonable agreement with previous measurements, while the weak thermal lens signal for the DMSO-rich mixture (c = 0.87) leads to 20% too large Soret coefficients with an uncertainty of more than 30%. Secondly we studied a liquid salt 1-ethyl-3-methylimidazolium ethylsulfate (EMIES) in butanol with a roughly ten times higher Soret coefficient of S(T) approximately 10(-2) K(-1). For this system we performed additional measurements with another experimental technique, the classical thermal diffusion forced Rayleigh scattering (TDFRS), which requires the addition of a small amount of dye to increase the absorption. In the entire investigated concentration range the results obtained with the TL and classical TDFRS technique agree within the error bars. As a third system we studied a non-ionic surfactant hexaethylene glycol monododecyl ether (C(12)E(6)) in water with a Soret coefficient of the order of S(T) approximately 10(-1) K(-1). For this system we find good agreement with previous measurements. We conclude that the TL technique is a reliable method for systems with a strong optical contrast and fairly large Soret coefficient of the order of S(T) approximately 10(-2) K(-1)