String theory on AdS3\boldsymbol{\text{AdS}_{\mathbf{3}}} and the symmetric orbifold of Liouville theory

For string theory on AdS$_3$ with pure NS-NS flux a complete set of DDF operators is constructed, from which one can read off the symmetry algebra of the spacetime CFT. Together with an analysis of the spacetime spectrum, this allows us to show that the CFT dual of superstring theory on ${\rm AdS}_3 \times {\rm S}^3 \times \mathbb{T}^4$ for generic NS-NS flux is the symmetric orbifold of $({\cal N}=4$ Liouville theory$)\times \mathbb{T}^4$. For the case of minimal flux ($k=1$), the Liouville factor disappears, and we just obtain the symmetric orbifold of $\mathbb{T}^4$, thereby giving further support to a previous claim. We also show that a similar analysis can be done for bosonic string theory on ${\rm AdS}_3 \times X$.Comment: 33+10 page

Strings on AdS3×S3×S3×S1\text{AdS}_3 \times \text{S}^3 \times \text{S}^3 \times \text{S}^1

String theory on ${\rm AdS}_3 \times {\rm S}^3 \times {\rm S}^3 \times {\rm S}^1$ with pure NS-NS flux and minimal flux through one of the two ${\rm S}^3$'s is studied from a world-sheet perspective. It is shown that the spacetime spectrum, as well as the algebra of spectrum generating operators, matches precisely that of the symmetric orbifold of ${\rm S}^3\times \mathrm{S}^1$ in the large $N$ limit. This gives strong support for the proposal that these two descriptions are exactly dual to one another.Comment: 25+23 page

The Worldsheet Dual of the Symmetric Product CFT

Superstring theory on ${\rm AdS}_3\times {\rm S}^3\times \mathbb{T}^4$ with the smallest amount of NS-NS flux (`$k=1$') is shown to be dual to the spacetime CFT given by the large $N$ limit of the free symmetric product orbifold $\mathrm{Sym}^N(\mathbb{T}^4)$. To define the worldsheet theory at $k=1$, we employ the hybrid formalism in which the ${\rm AdS}_3\times {\rm S}^3$ part is described by the $\mathfrak{psu}(1,1|2)_1$ WZW model (which is well defined). Unlike the case for $k\geq2$, it turns out that the string spectrum at $k=1$ does {\it not} exhibit the long string continuum, and perfectly matches with the large $N$ limit of the symmetric product. We also demonstrate that the fusion rules of the symmetric orbifold are reproduced from the worldsheet perspective. Our proposal therefore affords a tractable worldsheet description of a tensionless limit in string theory, for which the dual CFT is also explicitly known.Comment: 29+24 page

Higher spin algebras and large N=4\mathcal{N}=4 holography

A new family of higher spin algebras that arises upon restricting matrix extensions of $\mathfrak{shs}[\lambda]$ is found. We identify coset CFTs realising these symmetry algebras, and thus propose new higher spin-CFT dual pairs. These higher spin theories arise naturally as a subsector of string theory on ${\rm AdS}_3\times {\rm S}^3 \times {\rm S}^3 \times {\rm S}^1$ for specific ratios of the radii of the two spheres.Comment: 22 page

A holographic dual for string theory on AdS3×S3×S3×S1\mathrm{AdS}_3 \times \mathrm{S}^3 \times \mathrm{S}^3 \times \mathrm{S}^1

The CFT dual of string theory on $\mathrm{AdS}_3 \times \mathrm{S}^3 \times \mathrm{S}^3 \times \mathrm{S}^1$ is conjectured to be the symmetric orbifold of the $\mathcal{S}_\kappa$ theory, provided that one of the two $Q_5^\pm$ quantum numbers is a multiple of the other. We determine the BPS spectrum of the symmetric orbifold in detail, and show that it reproduces precisely the BPS spectrum that was recently calculated in supergravity. We also determine the BPS spectrum of the world-sheet theory that is formulated in terms of WZW models, and show that, apart from some gaps (which are reminiscent of those that appear in the corresponding $\mathbb{T}^4$ calculation), it also reproduces this BPS spectrum. In fact, the matching seems to work as well as for the familiar $\mathbb{T}^4$ case, and thus our results give strong support for this proposal.Comment: 41 pages, 2 figure

DOGMA 95 als Genre

In letzter Zeit ist es erstaunlich ruhig um DOGMA 95 geworden – jene Bewegung, die kurzfristig zu einer der wichtigsten Erneuerungsbestrebungen des europäischen Films avanciert war. Anfang des Jahres 2003 erschien im Spiegel ein großer Artikel, in dem Urs Jenny einen Abgesang auf DOGMA 95 anstimmte. Susanne Biers Film Open Hearts (2002) wurde zur gleichen Zeit vor allem deshalb wahrgenommen, weil der Film als vermeintlich letzter DOGMA-Film promotet wurde. Die Gründungsregisseure Lars von Trier und Thomas Vinterberg arbeiten längst an neuen Projekten, die mit dem "Schwur der Keuschheit" kaum noch etwas zu tun haben: Von Trier drehte mit Björk das Musical Dancer in the Dark (2000) und arbeitet nun für seinen neuen Film Dogville mit Hollywood-Ikone Nicole Kidman zusammen; Vinterberg hat gerade mit It's all about Love (2002) einen ästhetizistischen Science-Fiction-Film vorgestellt. Bereits im Sommer 2002 haben die beteiligten dänischen Produktionsfirmen ihr "DOGMA-Sekretariat" geschlossen. Als Grund wurde, neben den Kosten, die Herausbildung eines DOGMA-Genres genannt. Die dominante Rolle der DOGMA-Brüder bei der Interpretation der Regeln sei daran mitschuldig und solle durch ihr Verstummen aufgegeben werden

Group Membership, Competition, and Altruistic versus Antisocial Punishment: Evidence from Randomly Assigned Army Groups

We investigate how group boundaries, and the economic environment surrounding groups, affect altruistic cooperation and punishment behavior. Our study uses experiments conducted with 525 officers in the Swiss Army, and exploits random assignment to platoons. We find that, without competition between groups, individuals are more prone to cooperate altruistically in a prisoner's dilemma game with in-group as opposed to out-group members. They also use a costly punishment option to selectively harm those who defect, encouraging a norm of cooperation towards the group. Adding competition between groups causes even stronger in-group cooperation, but also a qualitative change in punishment: punishment becomes antisocial, harming cooperative and defecting out-group members alike. These findings support recent evolutionary models and have important organizational implications.group membership, competition, punishment, army, experiment

The perfect crime? : CCSVI not leaving a trace in MS

Background: Multiple sclerosis (MS) is a chronic, inflammatory demyelinating disease of the central nervous system, believed to be triggered by an autoimmune reaction to myelin. Recently, a fundamentally different pathomechanism termed ‘chronic cerebrospinal venous insufficiency’ (CCSVI) was proposed, provoking significant attention in the media and scientific community. Methods: Twenty MS patients (mean age 42.2±13.3 years; median Extended Disability Status Scale 3.0, range 0–6.5) were compared with 20 healthy controls. Extra- and intracranial venous flow direction was assessed by colour-coded duplex sonography, and extracranial venous cross-sectional area (VCSA) of the internal jugular and vertebral veins (IJV/VV) was measured in B-mode to assess the five previously proposed CCSVI criteria. IJV-VCSA≤0.3 cm2 indicated ‘stenosis,’ and IJV-VCSA decrease from supine to upright position ‘reverted postural control.’ The sonographer, data analyser and statistician were blinded to the patient/control status of the participants. Results: No participant showed retrograde flow of cervical or intracranial veins. IJV-VCSA≤0.3 cm2 was found in 13 MS patients versus 16 controls (p=0.48). A decrease in IJV-VCSA from supine to upright position was observed in all participants, but this denotes a physiological finding. No MS patient and one control had undetectable IJV flow despite deep inspiration (p=0.49). Only one healthy control and no MS patients fulfilled at least two criteria for CCSVI. Conclusions: This triple-blinded extra- and transcranial duplex sonographic assessment of cervical and cerebral veins does not provide supportive evidence for the presence of CCSVI in MS patients. The findings cast serious doubt on the concept of CCSVI in MS