118686725
Dynamical Model for Meson Production off Nucleon and Application to Neutrino‐Nucleus Reactions
I explain the Sato‐Lee (SL) model and its extension to the neutrino‐induced pion production off the nucleon. Then I discuss applications of the SL model to incoherent and coherent pion productions in the neutrino‐nucleus scattering. I mention a further extension of this approach with a dynamical coupled‐channels model developed in Excited Baryon Analysis Center of JLab.
119109289
Explanation of the More Effective Effective Field Theory
We show that the so-called more effective effective field theory (MEEFT) is essentially equivalent to the proper nuclear effective field theory (NEFT) in describing low-energy electroweak processes in nuclei. A key to understanding their equivalence is the relation between aN EFT-based NN -potential and a phenomenological potential through the Wilsonian renormalization group equation. We also discuss an important advantage of MEEFT.
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.
85451103
Extraction of Meson Resonances from Three-pions Photo-production Reactions
We have investigated the model dependence of meson resonance properties extracted from the Dalitz-plot analysis of the three-pions photoproduction reactions on the nucleon. Within a unitary model developed in Phys. Rev. D 84, 114019 (2011), we generate Dalitz-plot distributions as data to perform an isobar model fit that is similar to most of the previous analyses of three-pion production reactions. It is found that the resonance positions from the two models agree well when both fit the data accurately, except for the resonance poles near branch points. The residues of the resonant amplitudes extracted from the two models and by the usual Breit-Wigner procedure agree well only for the isolated resonances with narrow widths. For overlapping resonances, most of the extracted residues could be drastically different. Our results suggest that even with high precision data, the resonance extraction should be based on models within which the amplitude parametrization is constrained by three-particle unitarity condition.
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.
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.
121911984
Hydrodynamic Constants from Cosmic Censorship
We study a gravity dual of Bjorken flow of N = 4 SYM-theory plasma. We point out that the cosmic censorship hypothesis may explain why the regularity of the dual geometry constrains the hydrodynamic constants. We also investigate the apparent horizon of the dual geometry. We find that the dual geometry constructed on Fefferman-Graham (FG) coordinates is not appropriate for examination of the apparent horizon since the coordinates do not cover the trapped region. However, the preliminary analysis on FG coordinates suggests that the location of the apparent horizon is very sensitive to the hydrodynamic parameters.
18217443
Extension of boundary string field theory on disc and RP 2 worldsheet geometries
We present a construction of open-closed string field theory based on disc and RP 2 geometries. Finding an appropriate BRS operator in the case of the RP 2 geometry, we generalize the background independent open string field theory (or boundary string field theory) of Witten on a unit disc. The coupling constant flow at the closed string side is driven by the scalar operator inserted at the nontrivial loop of RP 2 . We discuss the off-shell extension of the boundary/crosscap states. Our construction provides an interpolation of orientifold planes of various dimensions as well as that of D-branes.
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.
118285847
Closed-string tachyon condensation and loop corrected on-shell effective action of open-string tachyons
We propose a basic strategy to obtain a consistent on-shell effective action of open-string tachyons, on the background where closed-string tachyons are already condensed. We use sigma-model approach, basically. We regard D-instanton-like objects with appropriate weight as closed-string tachyon tadpoles, and we insert them into worldsheets to analyze the effect of closed-string tachyons.
124882255
Nonequilibrium Phase Transitions in Gauge-Theory Plasma