Sarma Phase in Trapped Unbalanced Fermi Gases

We consider a trapped unbalanced Fermi gas at nonzero temperatures where the superfluid Sarma phase is stable. We determine in particular the phase boundaries between the superfluid, normal, and phase separated regions of the trapped unbalanced Fermi mixture. We show that the physics of the Sarma phase is sufficient to understand the recent observations of Zwierlein et al. [Science 311, 492 (2006); Nature 442, 54 (2006)] and indicate how the apparent contradictions between this experiment and the experiment of Partridge et al. [Science 311, 503 (2006)] may be resolved.Comment: Replaced with published version; 4 pages, 3 figure

Investigating the intrinsic noise limit of Dayem bridge NanoSQUIDs

NanoSQUIDs made from Nb thin films have been produced with nanometre loop sizes down to 200 nm, using weak-link junctions with dimensions less than 60 nm. These composite (W/Nb) single layer thin film devices, patterned by FIB milling, show extremely good low-noise performance ∼170 nΦ0 at temperatures between 5 and 8.5 K and can operate in rather high magnetic fields (at least up to 1 T). The devices produced so far have a limited operating temperature range, typically only 1–2 K. We have the goal of achieving operation at 4.2 K, to be compatible with the best SQUID series array (SSA) preamplifier available. Using the SSA to readout the nanoSQUIDs provides us with a means of investigating the intrinsic noise of the former. In this paper we report improved white noise levels of these nanoSQUIDs, enabling potential detection of a single electronic spin flip in a 1-Hz bandwidth. At low frequencies the noise performance is already limited by SSA preamplifier noise

Generalized gaugings and the field-antifield formalism

We discuss the algebra of general gauge theories that are described by the embedding tensor formalism. We compare the gauge transformations dependent and independent of an invariant action, and argue that the generic transformations lead to an infinitely reducible algebra. We connect the embedding tensor formalism to the field-antifield (or Batalin-Vilkovisky) formalism, which is the most general formulation known for general gauge theories and their quantization. The structure equations of the embedding tensor formalism are included in the master equation of the field-antifield formalism.Comment: 42 pages; v2: some clarifications and 1 reference added; version to be published in JHE

Symmetric Potentials of Gauged Supergravities in Diverse Dimensions and Coulomb Branch of Gauge Theories

A class of conformally flat and asymptotically anti-de Sitter geometries involving profiles of scalar fields is studied from the point of view of gauged supergravity. The scalars involved in the solutions parameterise the SL(N,R)/SO(N) submanifold of the full scalar coset of the gauged supergravity, and are described by a symmetric potential with a universal form. These geometries descend via consistent truncation from distributions of D3-branes, M2-branes, or M5-branes in ten or eleven dimensions. We exhibit analogous solutions asymptotic to AdS_6 which descend from the D4-D8-brane system. We obtain the related six-dimensional theory by consistent reduction from massive type IIA supergravity. All our geometries correspond to states in the Coulomb branch of the dual conformal field theories. We analyze linear fluctuations of minimally coupled scalars and find both discrete and continuous spectra, but always bounded below.Comment: Latex, 38 pages, minor correction

Regularisation, the BV method, and the antibracket cohomology

We review the Lagrangian Batalin--Vilkovisky method for gauge theories. This includes gauge fixing, quantisation and regularisation. We emphasize the role of cohomology of the antibracket operation. Our main example is $d=2$ gravity, for which we also discuss the solutions for the cohomology in the space of local integrals. This leads to the most general form for the action, for anomalies and for background charges.Comment: 12 pages, LaTeX, Preprint-KUL-TF-94/2

On BPS bounds in D=4 N=2 gauged supergravity II: general matter couplings and black hole masses

We continue the analysis of BPS bounds started in arXiv:1110.2688, extending it to the full class of N=2 gauged supergravity theories with arbitrary vector and hypermultiplets. We derive the general form of the asymptotic charges for asymptotically flat (M_4), anti-de Sitter (AdS_4), and magnetic anti-de Sitter (mAdS_4) spacetimes. Some particular examples from black hole physics are given to explicitly demonstrate how AdS and mAdS masses differ when solutions with non-trivial scalar profiles are considered.Comment: 21 pages; v2 added reference, published version; v3 minor correction

Cosmological Multi-Black Hole Solutions

We present simple, analytic solutions to the Einstein-Maxwell equation, which describe an arbitrary number of charged black holes in a spacetime with positive cosmological constant $\Lambda$. In the limit $\Lambda=0$, these solutions reduce to the well known Majumdar-Papapetrou (MP) solutions. Like the MP solutions, each black hole in a $\Lambda >0$ solution has charge $Q$ equal to its mass $M$, up to a possible overall sign. Unlike the $\Lambda = 0$ limit, however, solutions with $\Lambda >0$ are highly dynamical. The black holes move with respect to one another, following natural trajectories in the background deSitter spacetime. Black holes moving apart eventually go out of causal contact. Black holes on approaching trajectories ultimately merge. To our knowledge, these solutions give the first analytic description of coalescing black holes. Likewise, the thermodynamics of the $\Lambda >0$ solutions is quite interesting. Taken individually, a $|Q|=M$ black hole is in thermal equilibrium with the background deSitter Hawking radiation. With more than one black hole, because the solutions are not static, no global equilibrium temperature can be defined. In appropriate limits, however, when the black holes are either close together or far apart, approximate equilibrium states are established.Comment: 15 pages (phyzzx), UMHEP-380 (minor referencing error corrected

D-brane Wess--Zumino actions, T-duality and the cosmological constant

A geometrical formulation of the T-duality rules for type II superstring Ramond--Ramond fields is presented. This is used to derive the Wess-Zumino terms in superstring D-brane actions, including terms proportional to the mass parameter of the IIA theory, thereby completing partial results in the literature. For non-abelian world-volume gauge groups the massive type IIA D-brane actions contain non-abelian Chern--Simons terms for the Born--Infeld gauge potential, implying a quantization of the IIA cosmological constant.Comment: Version to be published in Physics Letters (minor corrections

Dirichlet-Branes and Ramond-Ramond Charges

We show that Dirichlet-branes, extended objects defined by mixed Dirichlet-Neumann boundary conditions in string theory, break half of the supersymmetries of the type~II superstring and carry a complete set of electric and magnetic Ramond-Ramond charges. We also find that the product of the electric and magnetic charges is a single Dirac unit, and that the quantum of charge takes the value required by string duality. This is strong evidence that the Dirchlet-branes are intrinsic to type II string theory and are the Ramond-Ramond sources required by string duality. We also note the existence of a previously overlooked 9-form potential in the IIa string, which gives rise to an effective cosmological constant of undetermined magnitude.Comment: LaTeX, 10 pages. Minor typos corrected in eq. 8, 9, 13. References added to [11