118556516
The boundary multiplet of N = 4 SU(2) ⊗ U(1) gauged supergravity on asymptotically-AdS5
We consider N =4 SU(2) ⊗ U(1) gauged supergravity on asymptotically-AdS5 backgrounds. By a near-boundary analysis we determine the boundary-dominant components of the bulk fields from their partially gauge-fixed field equations. Subdominant components are projected out in the boundary limit and we find a reduced set of boundary fields, constituting the N =2 Weyl multiplet. The residual bulk symmetries are found to act on the boundary fields as four-dimensional diffeomorphisms, N =2 supersymmetry and (super-) Weyl transformations. This shows that the on-shell N =4 supergravity multiplet yields the N =2 Weyl multiplet on the boundary with the appropriate local N =2 super-conformal transformations. Building on these results we use the AdS/CFT conjecture to calculate the Weyl anomaly of the dual four-dimensional superconformal field theories in a generic bosonic N =2 conformal supergravity background.
118522139
Spacetime noncommutativity in models with warped extradimensions
We construct consistent noncommutative (NC) deformations of the Randall-Sundrum spacetime that solve the NC Einstein equations with a non-trivial Poisson tensor depending on the fifth coordinate. In a class of these deformations where the Poisson tensor is exponentially localized on one of the branes (the NC-brane), we study the effects on bulk particles in terms of Lorentz-violating operators induced by NC-brane interactions. We sketch two models in which massive bulk particles mediate NC effects to an almost-commutative SM-brane, such that observables at high energy colliders are enhanced with respect to low energy and astrophysical observables.
118599677
High energy improved scalar quantum field theory from noncommutative geometry without UV/IR-mixing
We consider an interacting scalar quantum field theory on noncommutative Euclidean space. We implement a family of noncommutative deformations, which – in contrast to the well known Moyal-Weyl deformation – lead to a theory with modified kinetic term, while all local potentials are unaffected by the deformation. We show that our models, in particular, include propagators with anisotropic scaling z = 2 in the ultraviolet (UV). For a � 4 -theory on our noncommutative space we obtain an improved UV behaviour at the one-loop level and the absence of UV/IR-mixing and of the Landau pole.
119184636
Beyond the unitarity bound in AdS/CFT(A)dS
A bstractIn this work we expand on the holographic description of CFTs on de Sitter (dS) and anti-de Sitter (AdS) spacetimes and examine how violations of the unitarity bound in the boundary theory are recovered in the bulk physics. To this end we consider a Klein-Gordon field on AdSd+1 conformally compactified such that the boundary is (A)dSd, and choose masses and boundary conditions such that the corresponding boundary operator violates the CFT unitarity bound. The setup in which the boundary is AdSd exhibits a particularly interesting structure, since in this case the boundary itself has a boundary. The bulk theory turns out to crucially depend on the choice of boundary conditions on the boundary of the AdSd slices. Our main result is that violations to the unitarity bound in CFTs on dSd and AdSd are reflected in the bulk through the presence of ghost excitations. In addition, analyzing the setup with AdSd on the boundary allows us to draw conclusions on multi-layered AdS/CFT-type dualities.
12425682
Dirac operators on noncommutative curved spacetimes
We study the notion of a Dirac operator in the framework of twist-deformed noncommutative geometry. We provide a number of well-motivated candidate constructions and propose a minimal set of axioms that a noncommutative Dirac operator should satisfy. These criteria turn out to be restrictive, but they do not fix a unique construction: two of our operators generally satisfy the axioms, and we provide an explicit example where they are inequivalent. For highly symmetric spacetimes with Drinfeld twists constructed from sufficiently many Killing vector fields, all of our operators coincide. For general noncom- mutative curved spacetimes we find that demanding formal self-adjointness as an additional condition singles out a preferred choice among our candidates. Based on this noncommu- tative Dirac operator we construct a quantum field theory of Dirac fields. In the last part we study noncommutative Dirac operators on deformed Minkowski and AdS spacetimes as explicit examples.
118596724
Generalized gravitational entropy of probe branes: flavor entanglement holographically
A bstractThe notion of generalized gravitational entropy introduced by Lewkowycz and Maldacena allows, via the AdS/CFT correspondence, to calculate CFT entanglement entropies. We adapt the method to the case where flavor branes are present and treated in the probe approximation. This allows to calculate the leading flavor correction to the CFT entanglement entropy from the on-shell action of the probe, while dealing with the backreaction is avoided entirely and from the outset. As an application we give concise derivations for the contribution of massless and massive flavor degrees of freedom to the entanglement entropy in $ \mathcal{N} $ = 4 SYM theory.
119242094
Newton to Einstein — dust to dust
We investigate the relation between the standard Newtonian equations for a pressureless fluid (dust) and the Einstein equations in a double expansion in small scales and small metric perturbations. We find that parts of the Einstein equations can be rewritten as a closed system of two coupled differential equations for the scalar and transverse vector metric perturbations in Poisson gauge. It is then shown that this system is equivalent to the Newtonian system of continuity and Euler equations. Brustein and Riotto (2011) conjectured the equivalence of these systems in the special case where vector perturbations were neglected. We show that this approach does not lead to the Euler equation but to a physically different one with large deviations already in the 1-loop power spectrum. We show that it is also possible to consistently set to zero the vector perturbations which strongly constrains the allowed initial conditions, in particular excluding Gaussian ones such that inclusion of vector perturbations is inevitable in the cosmological context. In addition we derive nonlinear equations for the gravitational slip and tensor perturbations, thereby extending Newtonian gravity of a dust fluid to account for nonlinear light propagation effects and dust-induced gravitational waves.
118728953
Schrödinger method asN-body double and UV completion of dust
We investigate large-scale structure formation of collisionless dark matter in the phase space description based on the Vlasov equation whose nonlinearity is induced solely by gravitational interaction according to the Poisson equation. Determining the time-evolution of density and peculiar velocity demands solving the full Vlasov hierarchy for the moments of the phase space distribution function. In the presence of long-range interaction no consistent truncation of the hierarchy is known apart from the pressure- less fluid (dust) model which is incapable of describing virialization due to the occurrence of shell-crossing singularities and the inability to generate vorticity and higher cumulants like velocity dispersion. Our goal is to find a simple ansatz for the phase space distribution function that approximates the full Vlasov distribution function without pathologies in a controlled way and therefore can serve as theoretical N-body double and as a replacement for the dust model. We argue that the coarse-grained Wigner probability distribution obtained from a wave function fulfilling the Schr\"odinger-Poisson equation (SPE) is the sought-after function. We show that its evolution equation approximates the Vlasov equation and therefore also the dust equations before shell-crossing, but cures the shell-crossing singularities and is able to describe regions of multi-streaming and virialization. This feature was already employed in simulations by Widrow & Kaiser (1993). The coarse-grained Wigner ansatz allows to calculate all higher moments from density and velocity analytically, thereby incorporating nonzero higher cumulants in a self-consistent manner. On this basis we are able to show that the Schr\"odinger method (ScM) automatically closes the corresponding hierarchy such that it suffices to solve the SPE in order to directly determine density and velocity and all higher cumulants.