15481553
Bridging p-wave {pi} production and weak processes in few-nucleon systems with chiral perturbation theory
I study an aspect of chiral perturbation theory ({chi}PT) that enables one to 'bridge' different reactions. That is, an operator fixed in one of the reactions can then be used to predict the other. For this purpose, I calculate the partial-wave amplitude for the p-wave pion production (pp{yields}pn{pi}{sup +}) using the pion production operator from the lowest and the next nonvanishing orders. The operator includes a contact operator whose coupling has been fixed using a matrix element of a low-energy weak process (pp{yields}de{sup +}{nu}{sub e}). I find that this operator does not reproduce the partial-wave amplitude extracted from experimental data, showing that the bridging over the reactions with significantly different kinematics is not necessarily successful. I study the dependence of the amplitude on the various inputs such as the NN potential, the {pi}N{delta} coupling, and the cutoff. I argue the importance of a higher-order calculation. To gain an insight into a higher-order calculation, I add a higher-order counter term to the operator used above and fit the couplings to both the low-energy weak process and the pion production. The energy dependence of the partial-wave amplitude for the pion production is described by the operator consistently with the data. However, Imore » find a result that tells us to be careful about the convergence of the chiral expansion for the pp{yields}pn{pi}{sup +} reaction.« less
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.
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.
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.
1110514
Renormalization group analysis of nuclear force
We study a relation between nuclear forces based on phenomenological approach ( V ph ) and nuclear effective field theory ( V EFT ) from a viewpoint of renormalization group. We find the relation between these two types of nuclear force using Wilsonian renormalization group equation. Considering the fact that V EFT is defined in a certain small model space, we show that a simple contact interaction accurately simulates short-distance physics, and that V EFT is free from dependence on modelling the details of the short-distance physics. Based on our result, we discuss some features of nuclear effective field theory.
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.
29394289
A New Phase at a Finite Quark Density from AdS/CFT
We explore phases of N=2 super Yang-Mills theory at finite quark density by introducing quark chemical potential in a D3-D7 setup. We formulate the thermodynamics of brane embeddings and find that we need to renormalize the finite chemical potential due to the divergence of the thermodynamic potentials and we find that the density versus chemical potential equation of state has rich structure. This yields two distinct first order phase transitions in a small window of quark density. In order words, there is a new first order phase transition in the region of deconfined quarks. In this new phase, the chemical potential is a decreasing function of the density. We suggest that this might be relevant to the difference in sQGP--wQGP phases of QCD.
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.
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.
124882255
Nonequilibrium Phase Transitions in Gauge-Theory Plasma
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.