Final Report Summary - HQCD (Towards Holographic QCD and beyond)
The main objective of this project was to study various aspects of the AdS/CFT correspondence. In its original formulation in 1997 the correspondence describes duality between a ten dimensional string theory and a four dimensional supersymmetric gauge theory. Since 1997 the duality framework has been greatly extended to numerous cases of field theories other than four dimensional, with broken supersymmetry, no supersymmetry at all etc.
In our project we aimed at constructing a holographic model for quantum chromo-dynamics (QCD). The model incorporates numerous important features of the 'real-life' QCD, like, for instance, chiral symmetry and supersymmetry breaking, that so far has been ignored by most of the proposed holographic QCD models.
My main publication during the stay at the host institution which attacks this problem is properly titled 'On vector meson masses in a holographic SQCD'. Following the ideas outlined in my proposal, we studied probe flavor branes embedded in the so-called Klebanov-Strassler background. This embedding is controlled by a single complex parameter mu related to the quark mass. We investigated the spectrum of the vector mesons as a function of mu and compare it with the existing experimental data. We found a remarkable agreement with the masses of the lightest excited rho-mesons. Also, for a certain range of parameters our model exhibited an unusual intriguing behavior. The mesons built of the lighter quarks become heavier than the ones built of the heavier quarks. There is a possible connection this phenomenon may have with the masses of the putative pure strange-anti strange mesons.
The publication was a result of an international collaboration that involved European as well as American institutions (institute for advanced study at Princeton). An additional paper with almost the same collaboration, which directly follows the original proposal, was completed during my last months at the host institution and currently awaits a referee decision.
My research has not been limited only to the aforementioned model. I enjoyed a fruitful collaboration with other permanent and non-permanent members of the research group. This collaboration resulted in two more publications deeply related to my project.
In the first paper ('Stringy effects in black hole decay') were investigated stringy corrections to low energy decay rates of near-extremal charged black holes. We found perfect agreement between the microscopic and the macroscopic analysis of the decay processes. To arrive at this result we had to adapt and use holographic techniques developed recently in the context of the anti-de Sitter spaces (AdS)/conformal field theories (CFT) correspondence.
In the second paper ('The unconditional renormalisation group (RG) flow of the relativistic holographic fluid') we focused on another fast developing application of the AdS/CFT conjecture, the so-called fluid-gravity correspondence. Our setup consisted of asymptotically slowly varying perturbations of the AdS black brane in five-dimensional Einstein's gravity with a negative cosmological constant. In this setup the four dimensional holographic fluid lives on a radial cut-off surface. The position of the surface determines the energy scale of the field theory. Working in the one-derivative approximation we determined the RG flow of the transport coefficients of the fluid.
Finally, the remaining paper in the publication list ('(In) finite extensions of algebras from their Inonu-Wigner contractions') establishes an intriguing connection between the Inonu-Wigner contraction and the central extensions of the contracted algebra. This paper was a result of an international collaboration as well.
In our project we aimed at constructing a holographic model for quantum chromo-dynamics (QCD). The model incorporates numerous important features of the 'real-life' QCD, like, for instance, chiral symmetry and supersymmetry breaking, that so far has been ignored by most of the proposed holographic QCD models.
My main publication during the stay at the host institution which attacks this problem is properly titled 'On vector meson masses in a holographic SQCD'. Following the ideas outlined in my proposal, we studied probe flavor branes embedded in the so-called Klebanov-Strassler background. This embedding is controlled by a single complex parameter mu related to the quark mass. We investigated the spectrum of the vector mesons as a function of mu and compare it with the existing experimental data. We found a remarkable agreement with the masses of the lightest excited rho-mesons. Also, for a certain range of parameters our model exhibited an unusual intriguing behavior. The mesons built of the lighter quarks become heavier than the ones built of the heavier quarks. There is a possible connection this phenomenon may have with the masses of the putative pure strange-anti strange mesons.
The publication was a result of an international collaboration that involved European as well as American institutions (institute for advanced study at Princeton). An additional paper with almost the same collaboration, which directly follows the original proposal, was completed during my last months at the host institution and currently awaits a referee decision.
My research has not been limited only to the aforementioned model. I enjoyed a fruitful collaboration with other permanent and non-permanent members of the research group. This collaboration resulted in two more publications deeply related to my project.
In the first paper ('Stringy effects in black hole decay') were investigated stringy corrections to low energy decay rates of near-extremal charged black holes. We found perfect agreement between the microscopic and the macroscopic analysis of the decay processes. To arrive at this result we had to adapt and use holographic techniques developed recently in the context of the anti-de Sitter spaces (AdS)/conformal field theories (CFT) correspondence.
In the second paper ('The unconditional renormalisation group (RG) flow of the relativistic holographic fluid') we focused on another fast developing application of the AdS/CFT conjecture, the so-called fluid-gravity correspondence. Our setup consisted of asymptotically slowly varying perturbations of the AdS black brane in five-dimensional Einstein's gravity with a negative cosmological constant. In this setup the four dimensional holographic fluid lives on a radial cut-off surface. The position of the surface determines the energy scale of the field theory. Working in the one-derivative approximation we determined the RG flow of the transport coefficients of the fluid.
Finally, the remaining paper in the publication list ('(In) finite extensions of algebras from their Inonu-Wigner contractions') establishes an intriguing connection between the Inonu-Wigner contraction and the central extensions of the contracted algebra. This paper was a result of an international collaboration as well.