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J. -F. Yang

Publications and source records attributed to J. -F. Yang.

16 recordsLinked to original sources
arXiv2020

Covariant propagator and chiral power counting

Some one-loop diagrams with one and two external baryons/nucleons are revisited using covariant baryon propagators in chiral effective theory. We showed that it is enough to separate and subtract all the local terms that violate chiral power counting to recover chiral power counting, no need to introduce extra operations. The structures of leading chiral corrections and IR enhancement or threshold effects are 'stable' or persist as long as covariant propagators are employed for all particles.

hep-th↗
arXiv2014

Anomalous mapping between pionfull and pionless EFT's

The pion contributions to the coupling $C_0$ of pionless EFT are studied via both non-relativistic and relativistic forms of chiral effective field theory for nuclear forces. A definite item in the $2N$-reducible component of the box diagram is shown to be dominant over the $2N$-irreducible (potential) ones due to the pinching of low-lying nucleon poles, and this anomalous mapping between pionless and pionfull EFT's occurs right within the non-relativistic regime. A natural strategy for renormalization of the pionfull theory emerges as a byproduct through the interactive analysis of the box diagram. Such mapping perspective may shed some light on the efficient organization of the pionfull effective field theory for nuclear forces.

nucl-th↗
arXiv2013

$NN$ scattering in $^3S_1-^3D_1$ channels of EFT ($\notπ$)

The closed-form $T$ matrices in the $^3S_1$$-$$^3D_1$ channels of EFT($\not/!/!/pi$) for $NN$ scattering with the potentials truncated at order $\mathcal{O}(Q^4)$ are presented with the nonperturbative divergences parametrized in a general manner. The stringent constraints imposed by the closed form of the $T$ matrices are exploited in the underlying theory perspective and turned into virtues in the implementation of subtractions and the manifestation of power counting rules in nonperturbative regimes, leading us to the concept of EFT scenario. A number of scenarios of the EFT description of $NN$ scattering are compared with PSA data in terms of effective range expansion and $^3S_1$ phase shifts, showing that it is favorable to proceed in a scenario with conventional EFT couplings and sophisticated renormalization in order to have large $NN$ scattering lengths. The informative utilities of fine tuning are demonstrated in several examples and naturally interpreted in the underlying theory perspective. In addition, some of the approaches adopted in the recent literature are also addressed in the light of EFT scenario.

nucl-th↗
arXiv2009

A note on nonperturbative renormalization of effective field theory

Within the realm of contact potentials, the key structures intrinsic of nonperturbative renormalization of $T$-matrices are unraveled using rigorous solutions and an inverse form of algebraic Lippmann-schwinger equation. The intrinsic mismatches between effective field theory power counting and nonperturbative divergence structures are shown for the first time to preclude the conventional counterterm algorithm from working in the renormalization of EFT for $NN$ scattering in nonperturbative regimes.

hep-th↗
arXiv2009

A nonperturbative parametrization and scenario for EFT renormalization

We present a universal form of the $T$-matrices renormalized in nonperturbative regime and the ensuing notions and properties that fail conventional wisdoms. A universal scale is identified and shown to be renormalization group invariant. The effective range parameters are derived in a nonperturbative scenario with some new predictions within the realm of contact potentials. Some controversies are shown to be due to the failure of conventional wisdoms.

nucl-th↗
arXiv2009

Nonperturbative $^3S_1$-$^3D_1$ NN scattering in pionless EFT

The rigorous on-shell $T$-matrices for $NN$ scattering in the coupled channels $^3S_1$$-$$^3D_1$ are briefly presented in the context of EFT($\notπ$) with the contact potentials truncated at order $Δ=4$. The nonperturbative features of renormalization are highlighted and elaborated. A simple scenario for EFT power counting's and renormalization prescriptions is also presented with its consequences being roughly analyzed and discussed.

nucl-th↗
arXiv2007

Callan-Symanzik equations and low-energy theorems with trace anomalies

Basing on some new and concise forms of the Callan-Symanzik equations, the low-energy theorems involving trace anomalies à la Novikov-Shifman-Vainshtein-Zakharov, first advanced and proved in Nucl. Phys. \textbf{B165}, 67 (1980), \textbf{B191}, 301 (1981), are proved as immediate consequences. The proof is valid in any consistent effective field theories and these low-energy theorems are hence generalized. Some brief discussions about related topics are given.

hep-th↗
arXiv2007

Comparative analysis of non-perturbative effects in B -> X_u l anti-nu_l decays

In order to extract the Cabibbo-Kobayashi-Maskawa matrix element |V_{ub}| from B -> X_u l anti-nu_l decays, the overwhelming background from B -> X_c l anti-nu_l decays must be reduced by appropriate acceptance cuts. We study the non-perturbative effects due to the motion of the b quark inside the B meson on the phenomenologically relevant decay distributions of B -> X_u l anti-nu_l in the presence of such cuts in a comparative analysis based on shape functions and the parton model in the light-cone limit. Comparisons with recent data from the CLEO, BABAR, and BELLE collaborations favor the shape-function approach.

hep-ph↗
arXiv2006

Trace anomalies and chiral Ward identities

In a simple abelian spinor field theory, the canonical trace identities for certain axial-vector and axial-scalar operators are reexamined in dimensional regularization, some disagreements with previous results are found and an interesting new phenomenon is observed and briefly discussed.

hep-ph↗
arXiv2005

Renormalization of $NN$ scattering: contact potential

The renormalization of the $T$-matrix for $NN$ scattering with a contact potential is reexamined in a nonperturbative regime through rigorous nonperturbative solutions. Based on the underlying theory point of view, it is shown that the UV divergences in the nonperturbative solutions of the $T$-matrix should be subtracted through 'endogenous' counter terms, which in turn leads to a nontrivial prescription dependence. Moreover, employing the effective range expansion, the important procedure for imposing physical boundary conditions to remove the nontrivial prescription dependence is discussed and highlighted, especially before making physical claims. As byproducts, some relations between the effective range expansion parameters are derived. We also discussed the power counting of the couplings for the nucleon-nucleon interactions and other subtle points present within EFT framework beyond perturbative treatment.

nucl-th↗
arXiv2004

Renormalization of EFT for nucleon-nucleon scattering

The renormalization of EFT for nucleon-nucleon scattering in nonperturbative regimes is investigated in a compact parametrization of the $T$-matrix. The key difference between perturbative and nonperturbative renormalization is clarified. The underlying theory perspective and the 'fixing' of the prescriptions for the $T$-matrix from physical boundary conditions are stressed.

nucl-th↗
arXiv2004

Renormalization of EFT for nucleon-nucleon scattering

The renormalization of EFT for nucleon-nucleon scattering in nonperturbative regimes is investigated in a compact parametrization of the $T$-matrix. The key difference between perturbative and nonperturbative renormalization is clarified. The underlying theory perspective and the 'fixing' of the prescriptions for the $T$-matrix from physical boundary conditions are stressed.

nucl-th↗
arXiv2001

Dynamical symmetry breaking of massless $λϕ^4$ and renormalization scheme dependence

Through two loop effective potential we demonstrate that the $\bar{MS}$ scheme of dimensional regularization and Jackiw's prescription in cut-off regularization allow for the dynamical breaking solution in massless $λϕ^4$ theory, while the Coleman-Weinberg prescription does not. The beta function of the broken phase is negative, like in the one loop effective potential, but the UV fixed point is not zero, i.e., not an asymptotic freedom solution, unlike the one loop case. Some related issues were briefly discussed.

hep-ph↗