Phase diagram of the Holstein-Hubbard two-leg ladder using a functional renormalization-group method

The Local Potential Approximation (LPA) to the Wetterich-equation is formulated explicitly in terms of operators, which are invariant under the U (n)× U (n) symmetry group. Complete formulas are presented for the two-flavor ( U (2)× U (2)) case. The same approach leads to a unique natural truncation of the functional driving the renormalization flow of the potential of the three-flavor case ( U (3)× U (3)). The procedure applied to the SU (3)× SU (3) symmetric theory, results in an equation, which potentially allows an RG-investigation of the effect of the 't Hooft term representing the U A(1) anomaly, disentangled from the other operators.

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Optimized regulator for the quantized anharmonic oscillator

International Journal of Modern Physics A ◽

10.1142/s0217751x1550058x ◽

2015 ◽

Vol 30 (12) ◽

pp. 1550058 ◽

Cited By ~ 1

Author(s):

J. Kovacs ◽

S. Nagy ◽

K. Sailer

Keyword(s):

Renormalization Group ◽

Ground State ◽

Evolution Equations ◽

Energy Gap ◽

Anharmonic Oscillator ◽

Group Method ◽

Renormalization Group Method ◽

Functional Renormalization Group ◽

First Excited State ◽

Symmetric Phase

The energy gap between the first excited state and the ground state is calculated for the quantized anharmonic oscillator in the framework of the functional renormalization group method. The compactly supported smooth regulator is used which includes various types of regulators as limiting cases. It was found that the value of the energy gap depends on the regulator parameters. We argue that the optimization based on the disappearance of the false, broken symmetric phase of the model leads to the Litim's regulator. The least sensitivity on the regulator parameters leads, however, to an IR regulator being somewhat different of the Litim's one, but it can be described as a perturbatively improved, or generalized Litim's regulator and provides analytic evolution equations, too.

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The phase diagram of the multi-matrix model with ABAB interaction from functional renormalization

Journal of High Energy Physics ◽

10.1007/jhep12(2020)131 ◽

2020 ◽

Vol 2020 (12) ◽

Author(s):

Astrid Eichhorn ◽

Antonio D. Pereira ◽

Andreas G. A. Pithis

Keyword(s):

Phase Diagram ◽

Quantum Gravity ◽

Matrix Model ◽

Gravity Models ◽

Group Method ◽

Critical Properties ◽

Renormalization Group Method ◽

Functional Renormalization Group ◽

Tensor Models ◽

Practical Tool

Abstract At criticality, discrete quantum-gravity models are expected to give rise to continuum spacetime. Recent progress has established the functional renormalization group method in the context of such models as a practical tool to study their critical properties and to chart their phase diagrams. Here, we apply these techniques to the multi-matrix model with ABAB interaction potentially relevant for Lorentzian quantum gravity in 3 dimensions. We characterize the fixed-point structure and phase diagram of this model, paving the way for functional RG studies of more general multi-matrix or tensor models encoding causality and subjecting the technique to another strong test of its performance in discrete quantum gravity by comparing to known results.

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COUNTING STATISTICS OF NONEQUILIBRIUM TUNNELING PROCESS USING FUNCTIONAL RENORMALIZATION GROUP

International Journal of Modern Physics B ◽

10.1142/s0217979210054075 ◽

2010 ◽

Vol 24 (05) ◽

pp. 575-585 ◽

Cited By ~ 1

Author(s):

QING-QIANG XU ◽

BEN-LING GAO ◽

SHI-JIE XIONG

Keyword(s):

Renormalization Group ◽

Charge Transfer ◽

Quantum Dot ◽

Group Method ◽

Renormalization Group Method ◽

Functional Renormalization Group ◽

Nonequilibrium Transport ◽

Cumulant Generating Function ◽

Full Counting Statistics ◽

Counting Statistics

We develop a scheme to investigate the flux of nonequilibrium transport based on the full counting statistics and nonequilibrium functional renormalization group method. As an illustrative example, we study the charge transfer in the system of an interacting quantum dot connected to two noninteracting reservoirs via tunneling. Within the lowest approximation in functional renormalization group, we obtain the cumulant generating function analytically.

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