arXiv subjects

Y. Sumino

Publications and source records attributed to Y. Sumino.

58 records · Page 4Linked to original sources

arXiv1995

New Method for Exact Calculation of Green Functions in Scalar Field Theory

We present a new method for calculating the Green functions for a lattice scalar field theory in $D$ dimensions with arbitrary potential $V(ϕ)$. The method for non-perturbative evaluation of Green functions for $D \! = \! 1$ is generalized to higher dimensions. We define ``hole functions'' $A^{(i)}~(i=0,1,2,\cdots,N \! -\! 1)$ from which one can construct $N$-point Green functions. We derive characteristic equations of $A^{(i)}$ that form a {\it finite closed} set of coupled local equations. It is shown that the Green functions constructed from the solutions to the characteristic equations satisfy the Dyson-Schwinger equations. To fix the boundary conditions of $A^{(i)}$, a prescription is given for selecting the vacuum state at the boundaries.

hep-th↗

arXiv1995

Bern-Kosower Rule for Scalar QED

We derive a full Bern-Kosower-type rule for scalar QED starting from quantum field theory: we derive a set of rules for calculating $S$-matrix elements for any processes at any order of the coupling constant. Gauge-invariant set of diagrams in general is first written in the worldline path-integral expression. Then we integrate over $x(τ)$, and the resulting expression is given in terms of correlation function on the worldline $\left< x(τ) x(τ') \right>$. Simple rules to decompose the correlation function into basic elements are obtained. Gauge transformation known as integration by parts technique can be used to reduce the number of independent terms before integration over proper-time variables. The surface terms can be omitted provided the external scalars are on-shell. Also, we clarify correspondence to the conventional Feynman rule, which enabled us to avoid any ambiguity coming from the infinite dimensionality of the path-integral approach.

hep-ph↗

arXiv1995

Search for Dynamical Symmetry Breaking Physics by Using Top Quark

We report first results from the investigation on probing dynamical mechanism of the electroweak symmetry breaking using top quark. We consider the case where the top mass originates from a fermion-antifermion pair condensate, which necessitates (i)strong interaction to cause condensation, and (ii)4-fermi interaction to give top mass. From the observed top mass and the unitarity constraint, we obtain, for the 4-fermi interaction (ii), lower bounds for its strength and upper bounds for its intrinsic new mass scale as we vary the type of the strong interaction (i). Bethe-Salpeter and Schwinger-Dyson equations are solved numerically to study the dynamical symmetry breaking effect semi-quantitatively.

hep-ph↗

arXiv1994

Review on Physics of $e^+e^- \to t\bar{t}$ Near Threshold$^*$

We review the recent developments of studies on $e^+ e^- \to t\bar{t}$ in the threshold region. It has been shown that the top threshold cross sections will be able to provide many important and interesting physics. Due to the large mass and the large decay width of top quark, there will appear a number of unique features at top threshold. First, theoretical background is summarized. Then we present observables that are typical to the top threshold region, and discuss the physics that can be extracted. Also, we list the results of the recent parameter determination study taking a sample case of $m_t = 170$~GeV.

hep-ph↗