Imaginary part of the self-energy of a layered two-dimensional disordered electron gas

1995 ◽  
Vol 51 (14) ◽  
pp. 9038-9044 ◽  
Author(s):  
M. Crisan ◽  
L. Tǎtaru
Keyword(s):  
Imaginary Part ◽  
Electron Gas ◽  
The Self ◽  
Two Dimensional ◽  
Self Energy

scholarly journals Opacity from Loops in AdS

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
Alexandria Costantino ◽  
Sylvain Fichet
Keyword(s):  
Imaginary Part ◽  
Quantum Dynamics ◽  
Model Building ◽  
Asymptotic Properties ◽  
The Self ◽  
Effective Theory ◽  
Self Energy ◽  
Higher Dimensional ◽  
Timelike Region ◽  
Spectral Representations

Abstract We investigate how quantum dynamics affects the propagation of a scalar field in Lorentzian AdS. We work in momentum space, in which the propagator admits two spectral representations (denoted “conformal” and “momentum”) in addition to a closed-form one, and all have a simple split structure. Focusing on scalar bubbles, we compute the imaginary part of the self-energy ImΠ in the three representations, which involves the evaluation of seemingly very different objects. We explicitly prove their equivalence in any dimension, and derive some elementary and asymptotic properties of ImΠ.Using a WKB-like approach in the timelike region, we evaluate the propagator dressed with the imaginary part of the self-energy. We find that the dressing from loops exponentially dampens the propagator when one of the endpoints is in the IR region, rendering this region opaque to propagation. This suppression may have implications for field-theoretical model-building in AdS. We argue that in the effective theory (EFT) paradigm, opacity of the IR region induced by higher dimensional operators censors the region of EFT breakdown. This confirms earlier expectations from the literature. Specializing to AdS5, we determine a universal contribution to opacity from gravity.

scholarly journals Self-Consistent Calculation of Particle-Hole Diagrams on the Matsubara Frequency: Flex Approximation

1997 ◽  
Vol 08 (05) ◽  
pp. 1145-1158
Author(s):  
J. J. Rodríguez-Núñez ◽  
S. Schafroth
Keyword(s):  
Hubbard Model ◽  
Imaginary Part ◽  
Chemical Potential ◽  
Order Approximation ◽  
The Self ◽  
Green Functions ◽  
Matsubara Frequency ◽  
Self Energy ◽  
Peak Structure ◽  
Self Consistent

We implement the numerical method of summing Green function diagrams on the Matsubara frequency axis for the fluctuation exchange (FLEX) approximation. Our method has previously been applied to the attractive Hubbard model for low density. Here we apply our numerical algorithm to the Hubbard model close to half filling (ρ =0.40), and for T/t = 0.03, in order to study the dynamics of one- and two-particle Green functions. For the values of the chosen parameters we see the formation of three branches which we associate with the two-peak structure in the imaginary part of the self-energy. From the imaginary part of the self-energy we conclude that our system is a Fermi liquid (for the temperature investigated here), since Im Σ( k , ω) ≈ w2 around the chemical potential. We have compared our fully self-consistent FLEX solutions with a lower order approximation where the internal Green functions are approximated by free Green functions. These two approches, i.e., the fully self-consistent and the non-self-consistent ones give different results for the parameters considered here. However, they have similar global results for small densities.

Spin radiation effects in the BMT model of spinning charge

2014 ◽  
Vol 29 (31) ◽  
pp. 1450186 ◽  
Author(s):  
S. L. Lebedev
Keyword(s):  
Imaginary Part ◽  
Radiation Effects ◽  
Degrees Of Freedom ◽  
The Self ◽  
Spin Magnetic Moment ◽  
Self Energy ◽  
Radiation Processes ◽  
Nonzero Spin ◽  
Derivatives Of ◽  
Spin Contribution

The radiation processes emerging as a result of interaction between spin and orbit degrees of freedom of spinning charge are investigated with the use of the Bargmann–Michel–Telegdi (BMT) model. The spin contribution to the self-energy of the ultrarelativistic particle is imaginary and proportional to invariant constructed from the derivatives of the worldline and from the spin. This invariant determines up to negative numerical factor of the QED spin contribution to the imaginary part of the mass shift (MS). Particular cases of crossed, electric and magnetic external fields are considered in detail. The influence of an ideal boundary upon the self-energy of the particle is analyzed for the crossed field case. In the presence of the "mirror" the imaginary part of the MS gets an addition and the nonzero spin dependent real part appears, both however giving the small corrections to no-boundary MS. An alternative method to obtain the spin magnetic moment correction to the power of synchrotron radiation entails in generalization of the result known for the planar motion. Special attention is given to disagreement between classical and quantum pictures of spin radiation.

ANISOTROPIC PSEUDOGAP IN THE HALF-FILLING TWO-DIMENSIONAL HUBBARD MODEL AT FINITE TEMPERATURE

2000 ◽  
Vol 14 (21) ◽  
pp. 2271-2286
Author(s):  
TAIICHIRO SAIKAWA ◽  
ALVARO FERRAZ
Keyword(s):  
Fermi Surface ◽  
Fermi Level ◽  
Hubbard Model ◽  
Spectral Function ◽  
Density Of States ◽  
Spin Fluctuation ◽  
The Self ◽  
Two Dimensional ◽  
Self Energy ◽  
Half Filling

We have studied the pseudogap formation in the single-particle spectra of the half-filling two-dimensional Hubbard model. Using a Green's function with the one-loop self-energy correction of the spin and charge fluctuations, we have numerically calculated the self-energy, the spectral function, and the density of states in the weak-coupling regime at finite temperatures. Pseudogap formations have been observed in both the density of states and the spectral function at the Fermi level. The pseudogap in the spectral function is explained by the non-Fermi-liquid-like nature of the self-energy. The anomalous behavior in the self-energy is caused by both the strong antiferromagnetic spin fluctuation and the nesting condition on the non-interacting Fermi surface. In the present approximation, we find a logarithmic singularity in the integrand of the self-energy imaginary part. The pseudogap in the spectral function is highly momentum dependent on the Fermi surface. This anisotropy of the pseudogap is produced by the flatness of the band dispersion around the saddle point rather than the nesting condition on the Fermi level.

Über den Zusammenhang zwischen Selbstenergiefunktional und Ansprechfunktion eines wechselwirkenden Elektronengases

1969 ◽  
Vol 24 (12) ◽  
pp. 1871-1878
Author(s):  
W Kessel
Keyword(s):  
Integral Equation ◽  
Force Field ◽  
Response Function ◽  
Linear Functional ◽  
Electron Gas ◽  
Dyson Equation ◽  
Energy Functional ◽  
The Self ◽  
Applied Force ◽  
Self Energy

AbstractBy linearizing the Dyson equation of the electron gas in an externally applied force field an integral equation for the adiabatic response function is derived. Its relation to the electron self-energy is considered which leads to certain approximations in the response function if the self-energy functional is given. This is illustrated for the case that the self-energy is a linear functional of the electron Green's function.

SINGULAR FERMI SURFACES II: THE TWO-DIMENSIONAL CASE

2008 ◽  
Vol 20 (03) ◽  
pp. 275-334 ◽  
Author(s):  
JOEL FELDMAN ◽  
MANFRED SALMHOFER
Keyword(s):  
Perturbation Theory ◽  
Spatial Dimension ◽  
Physical Significance ◽  
The Self ◽  
Two Dimensional ◽  
Singular Case ◽  
Fermi Surfaces ◽  
Self Energy ◽  
Fermion Systems ◽  
Derivatives Of

We consider many-fermion systems with singular Fermi surfaces, which contain Van Hove points where the gradient of the band function k ↦ e(k) vanishes. In a previous paper, we have treated the case of spatial dimension d ≥ 3. In this paper, we focus on the more singular case d = 2 and establish properties of the fermionic self-energy to all orders in perturbation theory. We show that there is an asymmetry between the spatial and frequency derivatives of the self-energy. The derivative with respect to the Matsubara frequency diverges at the Van Hove points, but, surprisingly, the self-energy is C1 in the spatial momentum to all orders in perturbation theory, provided the Fermi surface is curved away from the Van Hove points. In a prototypical example, the second spatial derivative behaves similarly to the first frequency derivative. We discuss the physical significance of these findings.

scholarly journals Momentum structure of the self-energy and its parametrization for the two-dimensional Hubbard model

2016 ◽  
Vol 93 (19) ◽  
Author(s):  
P. Pudleiner ◽  
T. Schäfer ◽  
D. Rost ◽  
G. Li ◽  
K. Held ◽  
...  
Keyword(s):  
Hubbard Model ◽  
The Self ◽  
Two Dimensional ◽  
Self Energy
Sign in / Sign up

Export Citation Format

Share Document