Grants-Networking





Research Grants



Marie Curie Grant "RG x GRAV"



 

Understanding the dependence of physical systems on the length scale at which they are studied provides a powerful perspective formalised in the renormalization group (RG). This perspective can be used to reformulate this scale dependence as a flow in the space of quantum field theories. A remarkable feature of the renormalization group is its ability to characterise wildly different physical systems via a universal framework. Indeed, applications of the RG machinery appear across the energy spectrum, from electronic and atomic systems to the physics of interacting quarks and gluons. Despite its ubiquity in theoretical physics, some of the most interesting aspects of RG flow remain ill-understood. This is particularly true when the relevant deformation driving the RG flow explicitly breaks space-time symmetries of the UV theory.

Such deformations have the potential to be of great phenomenological interest. They can be used to explore the low energy physics of UV fixed point theories deformed by a lattice, or placed on a curved background. Additionally, they describe theories with localised defects, such as impurities or interfaces, as well as systems with boundaries. These systems arise in nearly all disciplines of contemporary physics research, including condensed matter, high energy particle physics, and cosmology. Accordingly, it is highly desirable to develop and extend RG techniques that are well suited to this class of flows, and can subsequently inform and advance our expectations of the physics in these diverse theories. This is the primary objective of this proposal.

In this action, we investigate such "non-relativistic RG flows" and advance our understanding of their properties along several significant directions. Among the most important conclusions of this research is the insight that techniques from supergravity can be used in concert with holographic duality to compute precision data for the IR endpoint of RG flows initiated by deforming superconformal theories with spatially varying couplings. Specifically, we showed that in such situations quantities like central charges which characterize the IR theory can be computed exactly without ever explicitly solving the gravitational equations. This surprising result represents not only an enormous technical simplification, but also extends and generalizes the validity of (defect) field theory results and hints at a more fundamental mathematical structure underlying such systems which has subsequently received considerable attention.

More information can be found at the dedicated website of the project.

The project has taken place entirely at CCTP.



HFRI grant "Gravity at its most extreme (AKRAIOS)"



 

In this project we will study the following two questions. First, what will one observe in the region far from an extreme black hole if the boundary of its near-horizon spacetime is deformed, while the interior is left intact? Second, what will one observe if the near-horizon spacetime is dynamically evolving, with conserved quantities on the event horizon, while the exterior is kept stationary?

In particular, we will identify and study the astrophysically relevant imprints of two universal gravitational aspects associated with the symmetries of two-dimensional AdS spacetime (AdS2). The first aspect is the existence of so-called "large diffeomorphisms," which are elements of a non-trivial asymptotic symmetry group. The second aspect is the existence of a kind of black hole hair for so-called "dynamical extreme black holes," which are seen numerically as possible endpoints of the nonlinear evolution of an instability of linear fields on extreme black hole horizons. As a result, we have two concrete research objectives for this project.

The first objective is for black holes with a near-horizon AdS2 part, such as near-extreme Kerr, to identify how the large diffeomorphisms of AdS2 manifest themselves in the far asymptotically flat region. We will specifically focus on deriving two associated observational signatures. Namely we will show that large AdS2 diffeomorphisms excite propagating gravitational waves in the far region and that they lead to gravitational memory effects.

The second objective is to write down analytically the metric for a dynamical extreme Kerr black hole. The dynamical extreme black hole exhibits 'hair' on its horizon in the form of conserved quantities which are distinct from the black hole's mass and angular momentum. This hair may be associated with the breaking of AdS2 large diffeomorphisms, induced by the connection with an asymptotically flat region.

The PI of this project is Achilleas Porfyriadis. The project will take place entirely at CCTP.



Research Networks



* The Center is a founding institution and is also coordinating the participation of Greek Scientists in the ESF network "HoloGrav" that pools efforts in the research area of the AdS/CFT correspondence (also known as gauge/gravity duality) worldwide. All major teams around the world are included.

The webpage of the Greek teams can be found here.

The funding of the network is targeted mainly for exchange visits and collaborations and the participation at the annual conference, the annual advanced school and the workshops that are supported by the network. More information can be found at the ESF network webpage.



* The Center is a participating and coordinating institution of the COST network The String Theory Universe. The full Memorandum of Understanding can be found here.

It is coordinated at a European level by Prof. Silvia Penati from the University of Milano.

The coordinators from the Greek side are Prof. Elias Kiritsis (CCTP) and Prof. Anastasios Petkou (University of Thessaloniki).

Substitute coordinators are Prof. Ioannis Bakas (NTUA) and Prof. Panagiota Kanti (University of Ioannina).

The members of the network from Greece can be found here. The list is dynamical and changes as a function of time.

The funding of the network is targeted mainly for exchange visits and collaborations and the participation at the COST conferences and workshops. More information can be found at the COST network webpage.



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Past Grants and Networks