A new approach to the functional integral formalism and its application to some simple physical problems

1989 ◽  
Vol 196 (2) ◽  
pp. 419
Keyword(s):  
Functional Integral ◽  
Integral Formalism ◽  
New Approach ◽  
Physical Problems ◽  
Functional Integral Formalism

An unified approach to inelastic light scattering in Keldysh–Schwinger functional integral formalism

2015 ◽  
Vol 29 (07) ◽  
pp. 1550040 ◽  
Author(s):  
Hyun Cheol Lee
Keyword(s):  
Light Scattering ◽  
Cross Sections ◽  
Golden Rule ◽  
Functional Integral ◽  
Integral Formalism ◽  
Inelastic Light Scattering ◽  
Scattering Geometry ◽  
The One ◽  
Resonant Part ◽  
Functional Integral Formalism

We propose a theoretical framework which can treat the nonresonant and the resonant inelastic light scattering on an equal footing in the form of correlation function, employing Keldysh–Schwinger functional integral formalism. The interference between the nonresonant and the resonant process can be also incorporated in this framework. This approach is applied to the magnetic Raman scattering of two-dimensional antiferromagnetic insulators. The entire set of the scattering cross-sections are obtained at finite temperature, the result for the resonant part agrees with the one obtained by the conventional Fermi golden rule at zero temperature. The interference contribution is shown to be very sensitive to the scattering geometry and the band structure.

Low-Temperature Spin Fluctuations beyond Spin Waves

2015 ◽  
Vol 233-234 ◽  
pp. 20-24 ◽  
Author(s):  
N.B. Melnikov ◽  
B.I. Reser
Keyword(s):  
Low Temperature ◽  
Spin Fluctuation ◽  
Functional Integral ◽  
Spin Fluctuations ◽  
Integral Formalism ◽  
Ferromagnetic Metals ◽  
Wave Approximation ◽  
Dynamic Spin ◽  
Functional Integral Formalism ◽  
Temperature Dynamic

A simple low-temperature dynamic spin-fluctuation theory of ferromagnetic metals is developed. The theory is based on the functional integral formalism for the multiband Hubbard Hamiltonian and takes into account both single-site and nonlocal spin fluctuations. We show that our approach correctly reproduces the T3/2 law at low temperatures. The calculated results of magnetic properties for Fe and Fe0.65Ni0.35 Invar demonstrate that the approach works on a much wider temperature interval than the spin-wave approximation.

Derivation of anomalous commutator in the functional integral formalism

1987 ◽  
Vol 73 (2) ◽  
pp. 1149-1151 ◽  
Author(s):  
A. Yu. Alekseev ◽  
Ya. Madaichik ◽  
L. D. Faddeev ◽  
S. L. Shatashvili
Keyword(s):  
Functional Integral ◽  
Integral Formalism ◽  
Functional Integral Formalism

scholarly journals A NEW DERIVATION OF THE COLEMAN–WEINBERG MECHANISM IN MASSLESS SCALAR QED

1996 ◽  
Vol 11 (09) ◽  
pp. 749-754 ◽  
Author(s):  
A.P.C. MALBOUISSON ◽  
F.S. NOGUEIRA ◽  
N.F. SVAITER
Keyword(s):  
Phase Transition ◽  
Effective Potential ◽  
Functional Integral ◽  
Massless Scalar ◽  
Integral Formalism ◽  
First Order ◽  
Unitary Gauge ◽  
Feynman Graphs ◽  
Functional Integral Formalism

We present a new derivation of the Coleman–Weinberg expression for the effective potential for massless scalar QED. Our result is obtained using the functional integral formalism, without expansions in Feynman graphs. We perform our calculations in the unitary gauge. The first-order character of the phase transition is established.

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