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001-es BibID:BIBFORM108058
035-os BibID:(cikkazonosító)12 (WOS)000820641000001 (Scopus)85133395748
Első szerző:Alexandre, J.
Cím:Renormalisation of non-differentiable potentials / J. Alexandre, N. Defenu, G. Grigolia, I. G. Márián, D. Mdinaradze, A. Trombettoni, Y. Turovtsi-Shiutev, I. Nándori
Dátum:2022
ISSN:1126-6708 1029-8479
Megjegyzések:Non-differentiable potentials, such as the V-shaped (linear) potential, appear in various areas of physics. For example, the effective action for branons in the framework of the brane world scenario contains a Liouville-type interaction, i.e., an exponential of the V-shaped function. Another example is coming from particle physics when the standard model Higgs potential is replaced by a periodic self-interaction of an N-component scalar field which depends on the length, thus it is O(N) symmetric. We first compare classical and quantum dynamics near non-analytic points and discuss in this context the role of quantum fluctuations. We then study the renormalisation of such potentials, focusing on the Exact Wilsonian Renormalisation approach, and we discuss how quantum fluctuations smoothen the bare singularity of the potential. Applications of these results to the non-differentiable effective branon potential and to the O(N) models when the spatial dimension is varied and to the O(N) extension of the sine-Gordon model in (1+1) dimensions are presented.
Tárgyszavak:Természettudományok Fizikai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
folyóiratcikk
Megjelenés:Journal of High Energy Physics. - 2022 : 7 (2022), p. 1-24. -
További szerzők:Defenu, N. Grigolia, G. Márián István Gábor (1992-) (fizikus) Mdinaradze, D. Trombettoni, Andrea Turovtsi-Shiutev, Y. Nándori István (1973-) (fizikus)
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2.

001-es BibID:BIBFORM088495
035-os BibID:(cikkazonosító)345002
Első szerző:Defenu, N.
Cím:Berezinskii-Kosterlitz-Thouless transition and criticality of an elliptic deformation of the sine-Gordon model / N. Defenu, V. Bacsó, I. G, Márián, I. Nándori, A. Trombettoni
Dátum:2019
ISSN:1751-8113 1751-8121
Megjegyzések:We introduce and study the properties of a periodic model interpolating between the sine-and the sinh-Gordon theories in 1 + 1 dimensions. This model shows the peculiarities, due to the preservation of the functional form of their potential across RG flows, of the two limiting cases: the sine-Gordon, not having conventional order/magnetization at finite temperature, but exhibiting Berezinskii?Kosterlitz?Thouless (BKT) transition; and the sinh-Gordon, not having a phase transition, but being integrable. The considered interpolation, which we term as sn-Gordon model, is performed with potentials written in terms of Jacobi functions. The critical properties of the sn-Gordon theory are discussed by a renormalization-group approach. The critical points, except the sinh-Gordon one, are found to be of BKT type. Explicit expressions for the critical coupling as a function of the elliptic modulus are given.
Tárgyszavak:Természettudományok Fizikai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
folyóiratcikk
Megjelenés:Journal of Physics A-Mathematical and Theoretical. - 52 : 34 (2019), p. 1-18. -
További szerzők:Borbélyné Bacsó Viktória (1975-) (fizika-matematika tanár) Márián István Gábor (1992-) (fizikus) Nándori István (1973-) (fizikus) Trombettoni, Andrea
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3.

001-es BibID:BIBFORM082933
035-os BibID:(cikkazonosító)141 (WoS)000355342600002 (Scopus)84930208464
Első szerző:Defenu, N.
Cím:Truncation effects in the functional renormalization group study of spontaneous symmetry breaking / N. Defenu, P. Mati, I. G. Márián, I. Nándori, A. Trombettoni
Dátum:2015
ISSN:1126-6708 1029-8479
Megjegyzések:We study the occurrence of spontaneous symmetry breaking (SSB) for O(N) models using functional renormalization group techniques. We show that even the local potential approximation (LPA) when treated exactly is sufficient to give qualitatively correct results for systems with continuous symmetry, in agreement with the Mermin-Wagner theorem and its extension to systems with fractional dimensions. For general N (including the Ising model N=1) we study the solutions of the LPA equations for various truncations using a finite number of terms (and different regulators), showing that SSB always occurs even where it should not. The SSB is signalled by Wilson-Fisher fixed points which for any truncation are shown to stay on the line defined by vanishing mass beta functions.
Tárgyszavak:Természettudományok Fizikai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
folyóiratcikk
Megjelenés:Journal of High Energy Physics. - 2015 : 5 (2015), p. 1-11. -
További szerzők:Mati Péter (1985-) (fizikus) Márián István Gábor (1992-) (fizikus) Nándori István (1973-) (fizikus) Trombettoni, Andrea
Pályázati támogatás:TÁMOP-4.2.4.A/ 2-11/1-2012-0001
TÁMOP
TÁMOP-4.2.1/B-09/1/KONV-2010-0007
TÁMOP
TÁMOP-4.2.2.C-11/1/KONV-2012-0010
TÁMOP
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4.

001-es BibID:BIBFORM108061
035-os BibID:(cikkazonosító)062 (WOS)000779813100006 (Scopus)85128410375
Első szerző:Márián István Gábor (fizikus)
Cím:Vacuum energy and renormalization of the field-independent term / I. G. Márián, U. D. Jentschura, N. Defenu, A. Trombettoni, I. Nándori
Dátum:2022
ISSN:1475-7516
Megjegyzések:Due to its construction, the nonperturbative renormalization group (RG) evolution of the constant, field-independent term (which is constant with respect to field variations but depends on the RG scale k) requires special care within the Functional Renormalization Group (FRG) approach. In several instances, the constant term of the potential has no physical meaning. However, there are special cases where it receives important applications. In low dimensions (d = 1), in a quantum mechanical model, this term is associated with the ground-state energy of the anharmonic oscillator. In higher dimensions (d = 4), it is identical to the A term of the Einstein equations and it plays a role in cosmic inflation. Thus, in statistical field theory, in flat space, the constant term could be associated with the free energy, while in curved space, it could be naturally associated with the cosmological constant. It is known that one has to use a subtraction method for the quantum anharmonic oscillator in d = 1 to remove the k 2 term that appears in the RG flow in its high-energy (UV) limit in order to recover the correct results for the ground-state energy. The subtraction is needed because the Gaussian fixed point is missing in the RG flow once the constant term is included. However, if the Gaussian fixed point is there, no further subtraction is required. Here, we propose a subtraction method for k(4) and k(2) terms of the UV scaling of the RG equations for d = 4 dimensions if the Gaussian fixed point is missing in the RG flow with the constant term. Finally, comments on the application of our results to cosmological models are provided.
Tárgyszavak:Természettudományok Fizikai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
folyóiratcikk
Megjelenés:Journal of Cosmology and Astroparticle Physics. - 2022 : 03 (2022), p. -. -
További szerzők:Jentschura, Ulrich David (fizikus) Defenu, N. Trombettoni, Andrea Nándori István (1973-) (fizikus)
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5.

001-es BibID:BIBFORM088494
035-os BibID:(cikkazonosító)114642
Első szerző:Márián István Gábor (fizikus)
Cím:Pseudo-periodic natural Higgs inflation / I. G. Márián, N. Defenu, U. D. Jentschura, A. Trombettoni, I. Nándori
Dátum:2019
ISSN:0550-3213
Megjegyzések:Inflationary cosmology represents a well-studied framework to describe the expansion of space in the early universe, as it explains the origin of the large-scale structure of the cosmos and the isotropy of the cosmic microwave background radiation. The recent detection of the Higgs boson renewed research activ- ities based on the assumption that the inflaton could be identified with the Higgs field. At the same time, the question whether the inflationary potential can be extended to the electroweak scale and whether it should be necessarily chosen ad hoc in order to be physically acceptable are at the center of an intense de- bate. Here, we propose and perform the slow-roll analysis of the so-called Massive Natural Inflation (MNI) model which has three adjustable parameters, the explicit mass term, a Fourier amplitude u, and a fre- quency parameter ?, in addition to a constant term of the potential. This theory has the advantage to present a structure of infinite non-degenerate minima and is amenable to an easy integration of high-energy modes. We show that, using PLANCK data, one can fix, in the large ?-region, the parameters of the model in a unique way. We also demonstrate that the value for the parameters chosen at the cosmological scale does not influence the results at the electroweak scale. We argue that other models can have similar properties both at cosmological and electroweak scales, but with the MNI model one can complete the theory towards low energies and easily perform the integration of modes up to the electroweak scale, producing the correct order-of-magnitude for the Higgs mass.
Tárgyszavak:Természettudományok Fizikai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
folyóiratcikk
Megjelenés:Nuclear Physics B. - 945 (2019), p. 1-19. -
További szerzők:Defenu, N. Jentschura, Ulrich David (fizikus) Trombettoni, Andrea Nándori István (1973-) (fizikus)
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6.

001-es BibID:BIBFORM088496
Első szerző:Márián István Gábor (fizikus)
Cím:Renormalization-group running induced cosmic inflation / I. G. Márián, N. Defenu, U. D. Jentschura, A. Trombettoni, I. Nándori
Dátum:2020
ISSN:1475-7516
Megjegyzések:As a contribution to a viable candidate for a standard model of cosmology, we here show that pre-inflationary quantum fluctuations can provide a scenario for the long- sought initial conditions for the inflaton field. Our proposal is based on the assumption that at very high energies (higher than the energy scale of inflation) the vacuum-expectation value (VeV) of the field is trapped in a false vacuum and then, due to renormalization-group (RG) running, the potential starts to flatten out toward low energy, eventually tending to a convex one which allows the field to roll down to the true vacuum. We argue that the proposed mechanism should apply to large classes of inflationary potentials with multiple concave regions. Our findings favor a particle physics origin of chaotic, large-field inflationary models as we eliminate the need for large field fluctuations at the GUT scale. In our analysis, we provide a specific example of such an inflationary potential, whose parameters can be tuned to reproduce the existing cosmological data with good accuracy.
Tárgyszavak:Természettudományok Fizikai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
folyóiratcikk
Megjelenés:Journal of Cosmology and Astroparticle Physics. - 2020 : 06 (2020), p. 028-028. -
További szerzők:Defenu, N. Jentschura, Ulrich David (fizikus) Trombettoni, Andrea Nándori István (1973-) (fizikus)
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