119155440
Holographic Mean-Field Theory for Baryon Many-Body Systems
We propose a new mean-field approach to analyze many-body systems of fermions in the gauge/gravity duality. We introduce a non-vanishing classical fermionic field in the gravity dual, which we call the holographic mean field. The holographic mean field reflects the dynamics of the fermions in the bulk, and generates the expectation values of the bi-linear operators of the boundary fermions. This enables us to analyze finite-density systems of baryons in the confinement phase. Our method provides a new bulk condition which relates the chemical potential to the charge density in the GKP-Witten prescription. Many-body physics of strongly-correlated fermions is one of the central subjects in modern physics. Stronglycorrelated fermions appear in various places, such as the systems of cold atoms, high-Tc superconductors, neutron stars and the quark-gluon plasma. However, the theoretical description of many-body systems of stronglycorrelated fermions is still a challenge owing to their non-perturbative natures. One of the successful computational frameworks for strongly-interacting fermions is the lattice gauge theory, but the Monte Carlo simulation at finite baryon density suffers from the sign problem. Recently, a great deal of attention has been paid to the AdS/CFT correspondence [1–3] or the holographic method because of its ability for non-perturbative computations and the absence of the sign problem. However, the current framework of the AdS/CFT correspondence still has room for improvement in dealing with the systems at finite baryon density, as we will explain later. It can be summarized as follows: 1) dynamical baryons at finite density have not been satisfactorily incorporated, and 2) the application of the GKP-Witten prescription [2, 3] to relate the baryon chemical potential to the baryon density has an ambiguity in the grand canonical ensemble. In the present paper, we shall propose a new approach, a holographic mean-field theory for fermions, to resolve these two problems. The self-consistent incorporation of dynamical baryons in our mean-field approach provides an eigenvalue equation which eliminates the ambiguity. We shall revisit the details of these problems below. The quarks are realized as fundamental strings attached to the flavor brane in the gravity dual [4]. Each end point of the strings carries a unit charge with respect to a U(1) gauge field on the flavor brane, and the quark density can be evaluated from the electric field in the radial direction at the boundary through the Gausslaw constraint. The quark chemical potential is thus the time component of the U(1) vector potential, A0, at the boundary, which is conjugate to the electric field [5, 6]. This fits the conventional GKP-Witten prescription: The boundary value of A0 gives the source (the chemical potential); the expectation value of the conjugate operator (the density) is given by the derivative of A0 at the boundary with respect to the radial direction. These quantities are boundary conditions for the Gauss-law constraint which may be chosen arbitrarily. However, another physical condition in the bulk, i.e., the bulk condition, fixes the ambiguity in the relationship between them whenever the GKP-Witten prescription works. To the best of the authors’ knowledge, only the example where the bulk condition is yet to be known is the finite density systems of baryons.
117758947
OFF-SHELL BOUNDARY/CROSSCAP STATES AND ORIENTIFOLD PLANES ∗
It is well-known that extending string theory off-shell is a hard problem. In the first quantized string theory based on an action of a single string, the guiding principle is a local Weyl invariance of string worldsheets. This immediately translates into on-shellness of string scattering amplitudes. Off-shellness alone does not suggest any particular symmetry and one has to consider insertions of operators carrying dimensions of arbitrarily high degrees on the bulk of the string worldsheets: this is a hard task to carry out. Situation can be more manageable to handle if the local Weyl invariance is broken only on the boundaries of the worldsheets. To date there are two proposals for off-shell string theory through deformation on the boundary of the string worldsheets. The one is the boundary string field theory (BSFT) of Witten [1] on a unit disc and the other is the sigma model approach of open strings to the spacetime action S. (See for example Ref. [2] and the references therein.) To put simply,
15165421
Descent relation of tachyon condensation from boundary string field theory
We analyze how lower-dimensional bosonic D-branes further decay, using the boundary string field theory. Especially we find that the effective tachyon potential of the lower-dimensional D-brane has the same profile as that of D25-brane.
119110586
Effective temperature of nonequilibrium dense matter in holography
We study properties of effective temperature of non-equilibrium steady states by using the anti-de Sitter spacetime/conformal field theory (AdS/CFT) correspondence. We consider non-equilibrium systems with a constant flow of current along an electric field, in which the current is carried by both the doped charges and those pair created by the electric field. We find that the effective temperature agrees with that of the Langevin systems if we take the limit where the pair creation is negligible. The effect of pair creation raises the effective temperature whereas the current by the doped charges contributes to lower the effective temperature in a wide range of the holographic models.
59125293
Negative Differential Resistivity from Holography
Negative differential resistivity (NDR) in a (3+1)-dimensional quantum system of strongly correlated charge carriers is theoretically reproduced by using the AdS/CFT correspondence. Our system is microscopically defined, and the analysis does not rely on any phenomenological models of NDR mechanism. The interaction between the heat reservoir and the nonequilibrium charge carriers is also taken into account. The system realizes insulation due to the formation of the neutral bound states of the charge carriers at low temperatures. However, the insulation is broken and the field-induced conductor phase appears by applying the external electric field greater than the critical value. We find that the NDR appears right above the critical electric field in this phase, and the pair creation of the charge carriers is crucial to realize the NDR. The present result suggests a possibility to observe a similar NDR in excitonic insulators or in the strongly interacting quark-gluon plasma, where the insulation originates in the formation of the neutral bound states. Subject Index: 121, 231, 346, 356
31657279
Gravity dual of spatially modulated phase
We show that the five-dimensional Maxwell theory with the Chern-Simons term is tachyonic in the presence of a constant electric field. When coupled to gravity, a sufficiently large Chern-Simons coupling causes instability of the Reissner-Nordstrom black holes in anti-de Sitter space. The instability happens only at nonvanishing momenta, suggesting a spatially modulated phase in the holographically dual quantum field theory in (3+1) dimensions, with spontaneous current generation in a helical configuration. The three-charge extremal black hole in the type IIB superstring theory on AdS_5×S^5 barely satisfies the stability condition.
118990154
Neutrino-induced meson productions off nucleon at forward limit in nucleon resonance region
We study forward neutrino-induced meson production off the nucleon in the resonance region. Our calculation is based on a dynamical coupled-channels (DCC) model that reasonably describes π(γ)N → πN, ηN, KΛ, KΣ data in the resonance region. We apply the PCAC hypothesis to the DCC model to relate the πN reaction amplitude to the forward neutrino reaction amplitude. In this way, we give a prediction for νN → πN, ππN, ηN, KΛ, KΣ reaction cross sections. The predicted νN → ππN, ηN, KΛ, KΣ cross sections are, for the first time, based on a model extensively tested by data. We compare our results with those from the Rein-Sehgal model that has been very often used in the existing Monte Carlo simulators for neutrino experiments. We find a significant difference between them.
117947270
Meson spectroscopy with unitary coupled-channels model for heavy-meson decay into three mesons
We develop a model for describing excited mesons decay into three mesons. The properties of the excited mesons can be extracted with this model. The model maintains the three-body unitarity that has been missed in previous data analyses based on the conventional isobar models. We study an importance of the three-body unitarity in extracting hadron properties from data. For this purpose, we use the unitary and isobar models to analyze the same pseudo data of gamma p -> pi+pi+pi-n, and extract the properties of excited mesons. We find a significant difference between the unitary and isobar models in the extracted properties of excited mesons, such as the mass, width and coupling strength to decay channels.
14437805
Consideration of nuclear forces from the viewpoint of the renormalization group: Relation of nuclear forces between phenomenological approach and nuclear effective field theory
A relation between nuclear forces derived using a phenomenological approach and nuclear effective field theory (NEFT) is proposed from a renormalization group point of view. A phenomenological nuclear force (V ph ) and an NEFT-based NN-potential (V EFT ) are satisfactorily related to each other through the Wilsonian renormalization group (WRG) method. It is clearly shown that use of the simple contact interactions in NEFT is adequate to simulate small scale phenomena, and that an NEFT-based NN-potential (V EFT ) is free from dependence on the model used to describe small scale phenomena. We study the characteristics of V EFT from a WRG point of view, emphasizing points that have not previously been fully recognized. We also use the V low k method and a unitary transformation method to relate V ph to V EFT . It is found that they are not appropriate for this purpose.
122375456
Renormalization group analysis of nuclear current operators
A Wilsonian renormalization group (WRG) equation for nuclear current operators in two-nucleon systems is derived. Nuclear current operators relevant to low-energy Gamow-Teller transitions are analyzed using the WRG equation. We employ the axial two-body current operators from phenomenological models and heavy-baryon chiral perturbation theory, which are quite different from one another in describing small-scale physics. After reducing the model space of the operators using the WRG equation, we find that there still remains a significant model dependence at {lambda}=200 MeV, where {lambda} is the sharp cutoff specifying the size of the model space. A model-independent effective current operator is found at a rather small cutoff value, {lambda}=70 MeV. By simulating the effective current operator at {lambda}=70 MeV, we obtain a current operator based on a pionless theory, thereby arguing that an equivalence relation exists between nuclear current operators of phenomenological models and those of effective field theories.
118487263
Effect of three‐pion unitarity on resonance poles from heavy meson decays
We study the final state interaction in 3π decay of meson resonances at the Excited Baryon Analysis Center (EBAC) of JLab. We apply the dynamical coupled‐channels formulation which has been extensively used by EBAC to extract N* information. The formulation satisfies the 3π unitarity condition which has been missed in the existing works with the isobar models. We report the effect of the 3π unitarity on the meson resonance pole positions and Dalitz plot.