It is possible that the standard model is coupled, through new massive charged or colored particles, to a hidden sector whose low energy dynamics is controlled by a pure Yang-Mills theory, with no light matter. Such a sector would have numerous metastable "hidden glueballs" built from the hidden gluons. These states would decay to particles of the standard model. We consider the phenomenology of this scenario, and find formulas for the lifetimes and branching ratios of the most important of these states. The dominant decays are to two standard model gauge bosons, or by radiative decays with photon emission, leading to jet-and photon-rich signals.

In the large Nc limit cold dense nuclear matter must be in a lattice phase. This applies also to holographic models of hadron physics. In a class of such models, like the generalized Sakai-Sugimoto model, baryons take the form of instantons of the effective flavor gauge theory that resides on probe flavor branes. In this paper we study the phase structure of baryonic crystals by analyzing discrete periodic configurations of such instantons. We find that instanton configurations exhibit a series of "popcorn" transitions upon increasing the density. Through these transitions normal (3D) lattices expand into the transverse dimension, eventually becoming a higher dimensional (4D) multi-layer lattice at large densities.We consider 3D lattices of zero size instantons as well as 1D periodic chains of finite size instantons, which serve as toy models of the full holographic systems. In particular, for the finite-size case we determine solutions of the corresponding ADHM equations for both a straight chain and for a 2D zigzag configuration where instantons pop up into the holographic dimension. At low density the system takes the form of an "abelian anti-ferromagnetic" straight periodic chain. Above a critical density there is a second order phase transition into a zigzag structure. An even higher density yields a rich phase space characterized by the formation of multi-layer zigzag structures. The finite size of the lattices in the transverse dimension is a signal of an emerging Fermi sea of quarks. We thus propose that the popcorn transitions indicate the onset of the "quarkyonic" phase of the cold dense nuclear matter.

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The Klebanov-Strassler background is invariant under the Z 2 symmetry I, which acts by exchanging the bi-fundamental fields A and B, accompanied by the charge conjugation. We study the background perturbations in the I-odd sector and find an exhaustive list of bosonic states invariant under the global SU(2)×SU(2) symmetry. In addition to the scalars identified in an earlier publication arXiv: 0712.4404 we find 7 families of massive states of spin 1. Together with the spin 0 states they form 3 families of massive vector multiplets and 2 families of massive gravitino multiplets, containing a vector, a pseudovector and fermions of spin 3/2 and 1/2. In the conformal Klebanov-Witten case these I-odd particles belong to the N = 1 superconformal Vector Multiplet I and Gravitino Multiplets II and IV. The operators dual to the I-odd singlet sector include those without bi-fundamental fields making an interesting connection with the pure N = 1 SYM theory. We calculate the mass spectrum of the corresponding glueballs numerically and discuss possible applications of our results. * Now at Tel Aviv University, Ramat Aviv 69978, IsraelThe Klebanov-Strassler supergravity solution, which corresponds to a certain vacuum of the SU(k(M + 1)) × SU(kM) gauge theory [1], provides an interesting and rich example of the gauge/string duality [2,3,4]. It generalizes the duality between the superconformal SU(N) × SU(N) gauge theory with bi-fundamentals and string theory on AdS 5 × T 1,1 [5].Adding extra colors to one of the gauge groups breaks the conformal symmetry [6,7,8] and leads to the cascade behavior [1,9,10]. The gauge group SU(k(M + 1)) × SU(kM) shrinks to SU(M) at the bottom of the cascade and the KS theory reduces to the pure gauge N = 1 SYM [1]. Unfortunately such a limit requires small g s M, which makes the supergravity approximation invalid. Nevertheless this connection between the KS solution and the pure super-Yang-Mills theory strongly motivates the studies of the bifundamental free sector of the SU(k(M +1))×SU(kM) theory that survives at the bottom of the cascade. The KS solution is invariant under the Z 2 symmetry I, which acts by exchanging the two two-spheres of the deformed conifold accompanied by the inversion of sign of the 3-form flux. On the field theory side this symmetry exchanges and conjugates the bi-fundamental fields A and B. Thus the KS solution corresponds to one particular Iinvariant vacuum |A| 2 = |B| 2 . The latter spontaneously breaks U(1) Baryon symmetry A → Ae ia , B → Be −ia . The corresponding massless Goldstone pseudoscalar a combines with the scalar U ∼ |A| 2 − |B| 2 into a I-odd scalar supermultiplet [11]. While a corresponds to the longitudinal part of the U(1) Baryon current J µ = ∂ µ a, the fluctuation of U changes the expectation values of the baryon operators A, B and moves the theory along the baryonic branch of the moduli space [11,12,13,14].The massless I-odd supermultiplet (U, a) was first studied in [11]. Later this analysis was generalized to the massive excitations in [15]. In partic...

In this paper we study the spectra of glueballs on the Klebanov-Strassler background and its extension to the baryonic branch. We numerically calculate the mass spectrum of glueballs from the spin 2 "gravity" multiplet, which contains the traceless part of the stress-energy tensor and the transverse part of the U (1) R-current. The mass spectra of the corresponding fluctuations in supergravity coincide due to supersymmetry, which is manifest in the effective five-dimensional theory through a Supersymmetric Quantum Mechanics transformation. We show that the glueball spectra grow as m 2 n ∝ U n 2 for large values of the baryonic branch parameter U .

In a wide class of holographic models, like the one proposed by Sakai and Sugimoto, baryons can be approximated by instantons of non-Abelian gauge fields that live on the world-volume of flavor D-branes. In the leading order, those are just the Yang-Mills instantons, whose solutions can be constructed from the celebrated Atiyah-Drinfeld-Hitchin-Manin (ADHM) construction. This fact can be used to study various properties of baryons in the holographic limit. In particular, one can attempt to construct a holographic description of the cold dense nuclear matter phase of baryons. It can be argued that holographic baryons in such a regime are necessarily in a solid crystalline phase. In this review, we summarize the known results on the construction and phases of crystals of the holographic baryons. Keywords: Cold dense nuclear matter; Sakai-Sugimoto model; holographic baryons; instantons. * Corresponding author. 1540052-1 Mod. Phys. Lett. B 2015.29. Downloaded from www.worldscientific.com by UNIVERSITY OF CALIFORNIA @ SANTA BARBARA on 08/23/15. For personal use only. V. Kaplunovsky, D. Melnikov & J. Sonnenschein 1540052-4 Mod. Phys. Lett. B 2015.29. Downloaded from www.worldscientific.com by UNIVERSITY OF CALIFORNIA @ SANTA BARBARA on 08/23/15. For personal use only. Holographic baryons and instanton crystalsdistances between the baryons, the repulsion is due to the fact that the lightest isoscalar vector, whose exchange yields repulsion, is lighter than the lightest scalar that yields attraction. In the near and intermediate zones, the interaction between two instantons of the SS model is purely repulsive. By using the gSS instead of the SS model, the severeness of the problem can be reduced. As was shown in Ref. 28 in the gSS (and not in the SS) model, there is, in addition to the repulsive force, also an attractive one due to an interaction of the instantons with a scalar field that associates with the fluctuation of the embedding, though the ratio of the attractive to repulsive potential can never exceed 1/9. Thus in both, the SS and the gSS nuclei will not be formed.In Ref. 37, it was shown that there is another holographic model 38 with a dominance of the attraction at long distances, but at the same time, a tiny ∼ 1.7% binding energy. In that model, the lightest scalar is in fact a pseudo-Goldstone boson associated with the spontaneous breaking of the scale symmetry. This meson can be made to be lighter, but not much lighter, than the lightest isoscalar vector and hence the emerging system is that of small attraction dominance. 37 The fact that in the gSS, the interaction between the baryons is for any separation distance repulsive will be important, but not crucial for this review, as we shall see in more detail later.Motivated by the interesting behavior of skyrmions at high density and being equipped with the new methodology of holography, in Refs. 29 and 30, the authors of this review decided to look at the problem of the cold nuclear matter from the holographic perspective. Conversely to the real nuclear m...

In this paper we study a simple gravity model dual to a 2 + 1-dimensional system with a boundary at finite charge density and temperature. In our naive AdS/BCF T extension of a well known AdS/CFT system a non-zero charge density must be supported by a magnetic field. As a result, the Hall conductivity is a constant inversely proportional to the coefficients of pertinent topological terms. Since the direct conductivity vanishes, such behaviors resemble that of a quantum Hall system with Fermi energy in the gap between the Landau levels. We further analyze the properties stemming from our holographic approach to a quantum Hall system. We find that at low temperatures the thermal and electric conductivities are related through the Wiedemann-Franz law, so that every charge conductance mode carries precisely one quantum of the heat conductance. From the computation of the edge currents we learn that the naive holographic model is dual to a gapless system if tensionless RS branes are used in the AdS/BCFT construction. To reconcile this result with the expected quantum Hall behavior we conclude that gravity solutions with tensionless RS branes must be unstable, calling for a search of more general solutions. We briefly discuss the expected features of more realistic holographic setups.

Entanglement is a special feature of the quantum world that reflects the existence of subtle, often non-local, correlations between local degrees of freedom. In topological theories such non-local correlations can be given a very intuitive interpretation: quantum entanglement of subsystems means that there are "strings" connecting them. More generally, an entangled state, or similarly, the density matrix of a mixed state, can be represented by cobordisms of topological spaces. Using a formal mathematical definition of TQFT we construct basic examples of entangled states and compute their von Neumann entropy. arXiv:1809.04574v1 [hep-th]