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001-es BibID:BIBFORM069606
Első szerző:Kovács József (fizikus)
Cím:Quantum-classical transition in the Caldeira-Leggett model / J. Kovács, B. Fazekas, S. Nagy, K. Sailer, K.
Dátum:2017
ISSN:0003-4916
Megjegyzések:The quantum-classical transition in the Caldeira-Leggett model is investigated in the framework of the functional renormalization group method. It is shown that a divergent quadratic term arises in the action due to the heat bath in the model. By removing the divergence with a frequency cutoff we considered the critical behavior of the model. The critical exponents belonging to the susceptibility and the correlation length are determined and their independence of the frequency cutoff and the renormalization scheme is shown.
Tárgyszavak:Természettudományok Fizikai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
renormalization
Megjelenés:Annals Of Physics 376 (2017), p. 372-381. -
További szerzők:Fazekas B. Nagy Sándor (1975-) (fizikus) Sailer Kornél (1951-) (fizikus)
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DOI
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001-es BibID:BIBFORM084627
Első szerző:Nagy Sándor (fizikus)
Cím:Lectures on renormalization and asymptotic safety / Nagy Sándor
Dátum:2014
ISSN:0003-4916
Megjegyzések:A short introduction is given on the functional renormalization group method, putting emphasis on its nonperturbative aspects. The method enables to find nontrivial fixed points in quantum field theoretic models which make them free from divergences and leads to the concept of asymptotic safety. It can be considered as a generalization of the asymptotic freedom which plays a key role in the perturbative renormalization. We summarize and give a short discussion of some important models, which are asymptotically safe such as the Gross-Neveu model, the nonlinear model, the sine-Gordon model, and we consider the model of quantum Einstein gravity which seems to show asymptotic safety, too. We also give a detailed analysis of infrared behavior of such scalar models where a spontaneous symmetry breaking takes place. The deep infrared behavior of the broken phase cannot be treated within the framework of perturbative calculations. We demonstrate that there exists an infrared fixed point in the broken phase which creates a new scaling regime there, however its structure is hidden by the singularity of the renormalization group equations. The theory spaces of these models show several similar properties, namely the models have the same phase and fixed point structure. The quantum Einstein gravity also exhibits similarities when considering the global aspects of its theory space since the appearing two phases there show analogies with the symmetric and the broken phases of the scalar models. These results be nicely uncovered by the functional renormalization group method.
Tárgyszavak:Természettudományok Fizikai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
folyóiratcikk
functional renormalization group
asymptotic safety
infrared fixed point
Megjelenés:Annals Of Physics. - 350 (2014), p. 310-346. -
Pályázati támogatás:TÁMOP-4.2.4.A/2-11-1-2012-0001
TÁMOP
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3.

001-es BibID:BIBFORM020949
Első szerző:Nagy Sándor (fizikus)
Cím:Functional renormalization group for quantized anharmonic oscillator / S. Nagy, K. Sailer
Dátum:2011
ISSN:0003-4916
Megjegyzések:Functional renormalization group methods formulated in the real-time formalism are applied to the O(N) symmetric quantum anharmonic oscillator, considered as a 0+1 dimensional quantum field-theoric model, in the next-to-leading order of the gradient expansion of the one- and two-particle irreducible effective action. The infrared scaling laws and the sensitivity-matrix analysis show the existence of only a single, symmetric phase. The Taylor expansion for the local potential converges fast while it is found not to work for the field-dependent wavefunction renormalization, in particular for the double-well bare potential. Results for the gap energy for the bare anharmonic oscillator potential hint on improving scheme-independence in the next-to-leading order of the gradient expansion, although the truncated perturbation expansion in the bare quartic coupling provides strongly scheme-dependent results for the infrared limits of the running couplings.
Tárgyszavak:Természettudományok Fizikai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
renormálási csoport
Megjelenés:Annals Of Physics. - 326 (2011), p. 1839-1876. -
További szerzők:Sailer Kornél (1951-) (fizikus)
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