Dynamics of First Order Transitions with Gravity Duals

A first order phase transition usually proceeds by nucleating bubbles of the new phase which then rapidly expand. In confining gauge theories with a gravity dual, the deconfined phase is often described by a black hole. If one starts in this phase and lowers the temperature, the usual description of how the phase transition proceeds violates the area theorem. We study the dynamics of this phase transition using the insights from the dual gravitational description, and resolve this apparent contradiction.Comment: 11 pages, 1 figure. v2: minor clarifications, reference adde

Flavor from M5-branes

We study various aspects of the defect conformal field theory that arises when placing a single M5-brane probe in AdS_4 x S^7. We derive the full set of fluctuation modes and dimensions of the corresponding dual operators. We argue that the latter does not depend on the presence of a non-trivial magnetic flux on the M5-brane world-volume. Finally we give a mass to the hypermultiplet living on the defect, and compute the resulting mesonic spectrum.Comment: 19 page

BMN Operators for N=1 Superconformal Yang-Mills Theories and Associated String Backgrounds

We study a class of near-BPS operators for a complex 2-parameter family of N=1 superconformal Yang-Mills theories that can be obtained by a Leigh-Strassler deformation of N=4 SYM theory. We identify these operators in the large N and large R-charge limit and compute their exact scaling dimensions using N=1 superspace methods. From these scaling dimensions we attempt to reverse-engineer the light-cone worldsheet theory that describes string propagation on the Penrose limit of the dual geometry.Comment: 47 pages, 1 figure, 1 table; v2 a few typos corrected; v3 added acknowledgements, a reference and improved discussion in section

Intersecting Flavor Branes

We consider an instance of the AdS/CFT duality where the bulk theory contains an open string tachyon, and study the instability from the viewpoint of the boundary field theory. We focus on the specific example of the AdS_5 X S^5 background with two probe D7 branes intersecting at general angles. For generic angles supersymmetry is completely broken and there is an open string tachyon between the branes. The field theory action for this system is obtained by coupling to N =4 super Yang-Mills two N =2 hyper multiplets in the fundamental representation of the SU(N) gauge group, but with different choices of embedding of the two N=2 subalgebras into N=4. On the field theory side we find a one-loop Coleman-Weinberg instability in the effective potential for the fundamental scalars. We identify a mesonic operator as the dual of the open string tachyon. By AdS/CFT, we predict the tachyon mass for small 't Hooft coupling (large bulk curvature) and confirm that it violates the AdS stability bound.Comment: 36 page

A World-Volume Perspective on the Recombination of Intersecting Branes

We study brane recombination for supersymmetric configurations of intersecting branes in terms of the world-volume field theory. This field theory contains an impurity, corresponding to the degrees of freedom localized at the intersection. The Higgs branch, on which the impurity fields condense, consists of vacua for which the intersection is deformed into a smooth calibrated manifold. We show this explicitly using a superspace formalism for which the calibration equations arise naturally from F- and D-flatness.Comment: References adde

Understanding why replacing I3–/I– by cobalt(II)/(III) electrolytes in bis(diimine)copper(I)-based dye-sensitized solar cells improves performance

The performances of dye-sensitized solar cells (DSCs) comprising heteroleptic bis(diimine)copper( I ) based dyes combined with either [Co(bpy) 3 ] 2+/3+ , [Co(phen) 3 ] 2+/3+ or I 3 /I redox mediators (bpy 1/4 2,2 0 - bipyridine, phen 1/4 1,10-phenanthroline) have been evaluated. The copper( I ) dyes contain the anchoring ligand ((6,6 0 -dimethyl-[2,2 0 -bipyridine]-4,4 0 -diyl)bis(4,1-phenylene))bis(phosphonic acid), 1, and an ancillary ligand (2, 3 or 4) with a 2,9-dimethyl-1,10-phenanthroline metal-binding domain. Ligands 2 and 3 include imidazole 2 0 -functionalities with 4-(diphenylamino)phenyl (2) or 4-(bis(4-n-butoxy) phenylamino)phenyl (3) domains; in 4, the phen unit is substituted in the 4,7-positions with holetransporting 4-(diphenylamino)phenyl groups. The photoconversion efficiency, h, of each of [Cu(1)(2)] + , [Cu(1)(3)] + and [Cu(1)(4)] + considerably improves by replacing the I 3 /I electrolyte by [Co(bpy) 3 ] 2+/3+ or [Co(phen) 3 ] 2+/3+ , and after a change of electrolyte solvent (MeCN to 3-methoxypropionitrile). Due to the faster charge transfer kinetics and more positive redox potential, the cobalt-based electrolytes are superior to the I 3 /I electrolyte in terms of open-circuit voltage (V OC ), short-circuit current (J SC ) and h; values of V OC 1/4 594 mV, J SC 1/4 9.58 mA cm 2 and h 1/4 3.69% (relative to h 1/4 7.12% for N719) are achieved for the best performing DSC which contains [Cu(1)(4)] + and [Co(bpy) 3 ] 2+/3+ . Corresponding values for [Cu(1)(4)] + and I 3 /I DSCs are 570–580 mV, 5.98–6.37 mA cm 2 and 2.43–2.62%. Electrochemical impedance spectroscopy (EIS) has been used to study DSCs with [Cu(1)(4)] + and the three electrolytes. EIS shows that the DSC with I 3 /I has the highest recombination resistance, whereas the [Co(phen) 3 ] 2+/3+ electrolyte gives the highest chemical capacitance and V OC and, between [Co(bpy) 3 ] 2+/3+ and [Co(phen) 3 ] 2+/3+ , the higher recombination resistance. The [Co(phen) 3 ] 2+/3+ electrolyte exhibits the highest mass transport restrictions which result in a lower J SC and DSC efficiency compared to the [Co(bpy) 3 ] 2+/3+ electrolyte

Copper(I) dye-sensitized solar cells with [Co(bpy)3]2+/3+ electrolyte

The hierarchical assembly of DSCs containing a new heteroleptic copper(I) complex with a phosphonic acid anchoring ligand is described; it is shown that conventional I−/I3− electrolytes may be replaced by [Co(bpy)3]2+/3+ with no loss in performance

Rigidity of SU(2,2|2)-symmetric solutions in Type IIB

We investigate the existence of half-BPS solutions in Type IIB supergravity which are invariant under the superalgebra SU(2,2|2) realized on either AdS_5 x S^2 x S^1 or AdS_5 x S^3 warped over a Riemann surface \Sigma with boundary. We prove that, in both cases, the only solution is AdS_5 x S^5 itself. We argue that this result provides evidence for the non-existence of fully back-reacted intersecting D3/D7 branes with either AdS_5 x S^2 x S^1 x \Sigma or AdS_5 x S^3 x \Sigma near-horizon limits.Comment: 55 page

Winding Strings and Decay of D-Branes with Flux

We study the boundary state associated with the decay of an unstable D-brane with uniform electric field, 1>e>0 in the string units. Compactifying the D-brane along the direction of the electric field, we find that the decay process is dominated by production of closed strings with some winding numbers; closed strings produced are such that the winding mode carries precisely the fraction $e$ of the individual string energy. This supports the conjecture that the final state at tree level is composed of winding strings with heavy oscillations turned on. As a corollary, we argue that the closed strings disperse into spacetime at a much slower rate than the case without electric field.Comment: 14 pages, harvmac, minor changes, clarified gauge choice, version to appear in JHE

Non-planar ABJM Theory and Integrability

Using an effective vertex method we explicitly derive the two-loop dilatation generator of ABJM theory in its SU(2)xSU(2) sector, including all non-planar corrections. Subsequently, we apply this generator to a series of finite length operators as well as to two different types of BMN operators. As in N=4 SYM, at the planar level the finite length operators are found to exhibit a degeneracy between certain pairs of operators with opposite parity - a degeneracy which can be attributed to the existence of an extra conserved charge and thus to the integrability of the planar theory. When non-planar corrections are taken into account the degeneracies between parity pairs disappear hinting the absence of higher conserved charges. The analysis of the BMN operators resembles that of N=4 SYM. Additional non-planar terms appear for BMN operators of finite length but once the strict BMN limit is taken these terms disappear.Comment: 1+26 pages, uses axodraw.sty. v2: typos fixed, references added. v3: more typos fixed, minor correction