We generalize the description of baryons as instantons of Sakai-Sugimoto model to the case where the flavor branes are non-anti-podal. The later corresponds to quarks with a "string endpoint mass". We show that the baryon vertex is located on the flavor branes and hence the generalized baryons also associate with instantons. We calculate the baryon mass spectra, the isoscalar and axial mean square radii, the isoscalar and isovector magnetic moments and the axial coupling as a function of the mass scale M_{KK} and the location ζof the tip of U-shaped flavor D8-branes. We determine the values of M_{KK} and ζfrom a best fit comparison with the experimental data. The later comes out to be in a forbidden region, which may indicate that the incorporation of baryons in Sakai-Sugimoto model has to be modified. We discuss the analogous baryons in a non-critical gravity model. A brief comment on the single flavor case (N_f=1) is also made.
We study solitons in the context of Sakai-Sugimoto-Witten holographic model of QCD. In the large 't Hooft coupling limit, flat space instantons give an approximate description of baryons. We provide an ansatz through deforming the BPST instanton by zero modes and obtain a subleading correction to the effective action. We also consider the quantum mechanical description of the collective coordinates. The correction term appears as a perturbation to the potential of the Hamiltonian and hence we can derive a first order correction to the mass spectrum of baryons.
We investigate a holographic realization in Type-IIB string theory of pure Chern-Simons theories, and focus on the level/rank dualities that they enjoy. The level/rank duality is established between the boundary theory, engineered utilizing D3-branes compactified on a $S^1$, and the theory on probe D7-branes located at a specific bulk location. Paying attention to the boundary conditions imposed on the Ramond-Ramond (RR) two- and six-forms, we show that holography precisely reproduces several different level/rank dual pairs. The $SL(2,\mathbf{Z})$ action relating all these theories is realized…
We study the di-baryon in the holographic QCD. The di-baryon is composed of six quarks and bound by the color interaction. In this paper, we adopt the Sakai-Sugimoto (SS) model as the holographic QCD to study the di-baryon. The SS model is formulated in a $\mathrm{D4}/\mathrm{D8}/\overline{\mathrm{D8}}$ system of the Type IIA string theory. It is expected that the di-baryon is described by the 2-instanton configuration of the flavor symmetry on D8-branes since the baryon number is identified as the instanton number. We will construct the 't Hooft 2-instanton solution explicitly and use it to d…
We present three different Type IIB AdS$_4$ Supergravity solutions, derived using the electrostatic-like problem formalism which preserves 8 Poincaré Supercharges. Two of these solutions correspond to the Abelian and non-Abelian T-duals of a Type IIA background, obtained from the dimensional reduction of 11D AdS$_4 \times S^7$ Supegravity. The third solution is a new background with some special properties. We compute the Page charges in each case, and provide brane set-up descriptions of the geometries. Also, we argue that the non-Abelian T-dual can be understood as a zoom-in of a more genera…
The shrinking of the bottomonium spectral function towards narrow quasi-particle states in a cooling strong-interaction medium at finite baryon density is followed within a holographic bottom-up model. The 5-dimensional Einstein-dilaton-Maxwell background is adjusted to lattice-QCD results of sound velocity and susceptibilities. The zero-temperature bottomonium spectral function is adjusted to experimental $Υ$ ground-state mass and first radial excitations. At baryo-chemical potential $μ_B = 0$, these two pillars let emerge the narrow quasi-particle state of the $Υ$ ground state at a temperatu…
We consider the noncommutative deformation of the finite temperature holographic QCD (Sakai--Sugimoto) model in external electric and magnetic field and evaluate the effect of the noncommutaivity on the properties of the conductor-insulator phase transition associated with a baryon number current. Although the noncommutative deformation of the gauge theory does not change the phase structure with respect to the baryon number current, the transition temperature $T_{c}$, the transition electric field $e_{c}$ and magnetic field $b_{c}$ in the conductor-insurator phase transition depend on the non…
Holographic phase transitions at finite chemical potential
最近，全息技术被用来研究N=2超杨-米尔斯理论的热性质，该理论具有规范群SU（Nc），耦合到基本物质的Nf << Nc味，在大Nc和大t Hooft耦合下。这里我们考虑相图作为温度和重子化学势μ的函数。对于固定的μ < Nc Mq there is a line of first order thermal phase transitions separating a region with vanishing baryon density and one with nonzero density. For fixed mu >Nc Mq，没有作为温度的函数的相变，并且重子密度总是非零的。我们还比较了巨正则系综和重子密度固定的正则系综的结果。
The Ryu-Takayanagi (RT) formula has been a key ingredient in our understanding of holography. Recent work on TT deformations has also boosted our understanding of holography away from the conformal boundary of AdS. In this short note, we aim to refine some recent work demonstrating the success of the RT formula in TT deformed theories. We emphasize general arguments that justify the use of the RT formula in general holographic theories that obey a GKPW-like dictionary. In doing so, we clarify subtleties related to holographic counterterms and discuss the implications for holography in general …
We explore entanglement negativity, a measure of the distillable entanglement contained in a quantum state, in relativistic field theories in various dimensions. We first give a general overview of negativity and its properties and then explain a well known result relating (logarithmic) negativity of pure quantum states to the Renyi entropy (at index $1/2$), by exploiting the simple features of entanglement in thermal states. In particular, we show that the negativity of the thermofield double state is given by the free energy difference of the system at temperature $T$ and $2\,T$ respectively…
We study the relationship between chiral symmetry breaking and baryons in holographic QCD. We construct a soliton with unit baryon charge in the presence of a nonzero mean value of the scalar bifundamental field, which is dual to the chiral condensate. We obtain a relation between the chiral condensate and the mass of the baryon and find in a clear-cut way that at large values of the condensate the holographic soliton is no longer located on the IR wall. Instead it is split into two halves, which are symmetrically located on the left and right flavor branes. On the other hand we find that the …
The Sakai-Sugimoto model is the most pre-eminent model of holographic QCD, in which baryons correspond to topological solitons in a five-dimensional bulk spacetime. Recently it has been shown that a single soliton in this model can be well approximated by a flat-space self-dual Yang-Mills instanton with a small size, although studies of multi-solitons and solitons at finite density are currently beyond numerical computations. A lower-dimensional analogue of the model has also been studied in which the Sakai-Sugimoto soliton is replaced by a baby Skyrmion in three spacetime dimensions with a wa…
We establish a holographic bottom-up model which covers both the baryonic and quark matter phases in cold and dense QCD. This is obtained by including the baryons using simple approximation schemes in the V-QCD model, which also includes the backreaction of the quark matter to the dynamics of pure Yang-Mills. We examine two approaches for homogeneous baryon matter: baryons as a thin layer of noninteracting matter in the holographic bulk, and baryons with a homogeneous bulk gauge field. We find that the second approach exhibits phenomenologically reasonable features. At zero temperature, the va…
We present an analysis of the three-flavor holographic model of QCD associated to a $D4/D8$ brane configuration, with symmetry breaking induced by a worldsheet instanton associated to a closed loop connecting $D4-D8-D6-\overline{D8}$. We calculate the electromagnetic and axial couplings of all octet and decuplet baryons, as well as several negative parity excitations, with and without symmetry breaking effects, and demonstrate qualitative and quantitative agreement with many available experimental measurements, with marked improvement over the analogous two-flavor models.
