Estudo Geralhttps://estudogeral.uc.ptThe DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material.Wed, 21 Feb 2024 06:06:26 GMT2024-02-21T06:06:26Z50191Top condensation model: a step towards the correct prediction of the Higgs masshttps://hdl.handle.net/10316/106073Title: Top condensation model: a step towards the correct prediction of the Higgs mass
Authors: Osipov, A. A.; Hiller, B.; Blin, A. H.; Palanga, F.; Moreira, J.; Sampaio, M.
Abstract: A realization of the composite Higgs scenario in
the context of the effective model with the SU(2)L ×U(1)R
symmetric four-Fermi interactions proposed by Miransky,
Tanabashi and Yamawaki is studied. The model implements
Nambu’s mechanism of dynamical electroweak symmetry
breaking leading to the formation of ¯tt and ¯ bb quark condensates.
We explore the vacuum structure and spectrum of
the model by using the Schwinger proper-time method. As
a direct consequence of this mechanism, the Higgs acquires
a mass in accord with its experimental value. The present
prediction essentially differs from the known overestimated
value, mχ = 2mt , making more favourable the top condensation
scenario presented here. The mass formulas for the
members of the second Higgs doublet are also obtained. The
Nambu sum rule is discussed. It is shown that the anomalous
U(1)A symmetry breaking modifies this rule at next to
leading order in 1/Nc.
Wed, 01 Jan 2020 00:00:00 GMThttps://hdl.handle.net/10316/1060732020-01-01T00:00:00ZNonuniform phases in a three-flavor Nambu–Jona-Lasinio modelhttps://hdl.handle.net/10316/46567Title: Nonuniform phases in a three-flavor Nambu–Jona-Lasinio model
Authors: Moreira, J.; Hiller, B.; Broniowski, W.; Osipov, A. A.; Blin, A. H.
Mon, 24 Feb 2014 00:00:00 GMThttps://hdl.handle.net/10316/465672014-02-24T00:00:00ZA general framework to diagonalize vector–scalar and axial-vector–pseudoscalar transitions in the effective meson Lagrangianhttps://hdl.handle.net/10316/46708Title: A general framework to diagonalize vector–scalar and axial-vector–pseudoscalar transitions in the effective meson Lagrangian
Authors: Morais, J.; Hiller, B.; Osipov, A. A.
Wed, 23 Aug 2017 00:00:00 GMThttps://hdl.handle.net/10316/467082017-08-23T00:00:00ZStrange quark matter in the presence of explicit symmetry breaking interactionshttps://hdl.handle.net/10316/46532Title: Strange quark matter in the presence of explicit symmetry breaking interactions
Authors: Moreira, J.; Morais, J.; Hiller, B.; Osipov, A. A.; Blin, A. H.
Wed, 10 Jun 2015 00:00:00 GMThttps://hdl.handle.net/10316/465322015-06-10T00:00:00Zπ 0 − η − η ′ mixing in a generalized multiquark interaction schemehttps://hdl.handle.net/10316/46496Title: π 0 − η − η ′ mixing in a generalized multiquark interaction scheme
Authors: Osipov, A. A.; Hiller, B.; Blin, A. H.
Fri, 24 Jun 2016 00:00:00 GMThttps://hdl.handle.net/10316/464962016-06-24T00:00:00ZImplications of a new effective chiral meson Lagrangianhttps://hdl.handle.net/10316/4496Title: Implications of a new effective chiral meson Lagrangian
Authors: Osipov, Alexander A.; Sampaio, Marcos; Hiller, Brigitte
Abstract: Based on a recently derived effective chiral meson Lagrangian from the extended SU(2)[circle times operator]SU(2) Nambu-Jona-Lasinio (ENJL) model, in the linear realization of chiral symmetry, we extract to leading order in the 1/Nc expansion all associated relevant three-point functions [rho]-->[pi][pi], [sigma]-->[pi][pi], a1-->[rho][pi], a1-->[sigma][pi], as well as the amplitude for [pi][pi] scattering. We discuss the formal differences of these amplitudes as compared with those derived in the literature and calculate the associated decay widths and scattering parameters. The differences have two origins:
Tue, 01 Jan 2002 00:00:00 GMThttps://hdl.handle.net/10316/44962002-01-01T00:00:00ZPath integral bosonization of the 't Hooft determinant: fluctuations and multiple vacuahttps://hdl.handle.net/10316/4490Title: Path integral bosonization of the 't Hooft determinant: fluctuations and multiple vacua
Authors: Osipov, Alexander A.; Hiller, Brigitte
Abstract: The 't Hooft six-quark flavor mixing interaction (Nf=3) is bosonized by the path integral method. The considered complete Lagrangian is constructed on the basis of the combined 't Hooft and U(3)Ã—U(3) extended chiral four fermion Nambu-Jona-Lasinio interactions. The method of the steepest descents is used to derive the effective mesonic Lagrangian. Additionally to the known lowest order stationary phase (SP) result of Reinhardt and Alkofer we obtain the contribution from the small quantum fluctuations of bosonic configurations around their stationary phase trajectories. It affects the vacuum state of hadrons at low energies: whereas without the inclusion of quantum fluctuations the vacuum is uniquely defined for a fixed set of the model parameters, fluctuations give rise to multivalued solutions of the gap equations, marked at instances by drastic changes in the quark condensates. We derive the new gap equations and analyze them in comparison with known results. We classify the solutions according to the number of extrema they may accommodate. We find up to four solutions in the 0<mu,ms<3Â GeV region.
Tue, 01 Jan 2002 00:00:00 GMThttps://hdl.handle.net/10316/44902002-01-01T00:00:00ZInverse mass expansion of the one-loop effective actionhttps://hdl.handle.net/10316/4510Title: Inverse mass expansion of the one-loop effective action
Authors: Osipov, Alexander A.; Hiller, Brigitte
Abstract: A method is described for the development of the one-loop effective action expansion as an asymptotic series in inverse powers of the fermion mass. The method is based on the Schwinger-DeWitt proper-time technique, which allows for loop particles with nondegenerate masses. The case with SU(2)×SU(2) as the symmetry group is considered. The obtained novel series generalizes the well-known Schwinger-DeWitt inverse mass expansion for equal masses, and is chiral invariant at each order. We calculate the asymptotic coefficients up to the fifth order and clarify their relationship with the standard Seeley-DeWitt coefficients.
Mon, 01 Jan 2001 00:00:00 GMThttps://hdl.handle.net/10316/45102001-01-01T00:00:00ZThe role of hidden ambiguities in the linear sigma model with fermionshttps://hdl.handle.net/10316/4406Title: The role of hidden ambiguities in the linear sigma model with fermions
Authors: Hiller, Brigitte; Mota, A. L.; Nemes, M. C.; Osipov, Alexander A.; Sampaio, Marcos
Abstract: The UL(3)×UR(3) linear sigma model (LSM) with quark degrees of freedom is used to show that radiative corrections generate undetermined finite contributions. Their origin is related to surface terms which are differences between divergent integrals with the same degree of divergence. The technique used to detect these ambiguities is an implicit regularization on basic divergent integrals that do not depend on external momenta. We show that such contributions are absorbed by renormalization or fixed by symmetry requirements. The general expression for surface terms is derived. Renormalization group coefficients are calculated, as well as relevant observables for this model, such as f[pi], f[kappa] and the pion and kaon form factors.
Sun, 01 Jan 2006 00:00:00 GMThttps://hdl.handle.net/10316/44062006-01-01T00:00:00ZOne-loop fermion determinant with explicit chiral symmetry breakinghttps://hdl.handle.net/10316/4525Title: One-loop fermion determinant with explicit chiral symmetry breaking
Authors: Osipov, Alexander A.; Hiller, Brigitte
Abstract: We use a proper-time regularization to define the real part of the one-loop fermion determinant for the case in which explicit chiral symmetry breaking takes place. We demonstrate that beyond the chiral limit the standard definition of Re[lndetD] by lndetD deforms the symmetry breaking pattern of the basic fermionic Lagrangian. We show how to obtain the correcting functional in order to arrive at the fermion determinant whose transformation properties are consistent with the general symmetry requirements. As an example it is shown how the fundamental symmetries and the explicit chiral symmetry breaking pattern associated with the ENJL model are consistently preserved in this way.
Sat, 01 Jan 2000 00:00:00 GMThttps://hdl.handle.net/10316/45252000-01-01T00:00:00ZOne-loop determinant of Dirac operator in non-renormalizable modelshttps://hdl.handle.net/10316/4537Title: One-loop determinant of Dirac operator in non-renormalizable models
Authors: Osipov, A. A.; Hiller, B.; Blin, A. H.
Abstract: We use proper-time regularizations to define the one-loop fermion determinant in the form suggested by Gasser and Leutwyler some years ago. We show how to obtain the polynomial by which this definition of ln detD needs to be modified in order to arrive at the fermion determinant whose modulus is invariant under chiral transformations. As an example it is shown how the fundamental symmetries associated with the NJL model are preserved in a consistent way.
Sat, 01 Jan 2000 00:00:00 GMThttps://hdl.handle.net/10316/45372000-01-01T00:00:00ZOZI violating eight-quark interactions as a thermometer for chiral transitionshttps://hdl.handle.net/10316/4339Title: OZI violating eight-quark interactions as a thermometer for chiral transitions
Authors: Osipov, A. A.; Hiller, B.; Moreira, J.; Blin, A. H.
Abstract: This work is a follow-up of our recent observation that in the SU(3) flavor limit with vanishing current quark masses the temperature for the chiral transition is substantially reduced by adding eight-quark interactions to the Nambu-Jona-Lasinio Lagrangian with UA(1) breaking. Here we generalize the case to realistic light and strange quark masses and confirm our prior result. Additionally, we demonstrate that depending on the strength of OZI violating eight-quark interactions, the system undergoes either a rapid crossover or a first order phase transition. The meson mass spectra of the low lying pseudoscalars and scalars at T=0 are not sensitive to the difference in the parameter settings that correspond to these two alternatives, except for the singlet-octet mixing scalar channels, mainly the [sigma] meson.
Tue, 01 Jan 2008 00:00:00 GMThttps://hdl.handle.net/10316/43392008-01-01T00:00:00ZPath integral bosonization of the ‘t Hooft determinant: quasi-classical correctionshttps://hdl.handle.net/10316/7697Title: Path integral bosonization of the ‘t Hooft determinant: quasi-classical corrections
Authors: Osipov, A. A.; Hiller, B.
Abstract: The many-fermion Lagrangian which includes the ‘t Hooft six-quark flavor mixing interaction ( N f = 3) and the U L(3) x U R(3) chiral symmetric four-quark Nambu-Jona-Lasinio- (NJL-) type interactions is bosonized by the path integral method. The method of the steepest descents is used to derive the effective quark-mesonic Lagrangian with linearized many-fermion vertices. We obtain, additionally to the known lowest order stationary phase result of Reinhardt and Alkofer, the next to leading order (NLO) contribution arising from quantum fluctuations of auxiliary bosonic fields around their stationary phase trajectories (the Gaussian integral contribution). Using the gap equation we construct the effective potential, from which the structure of the vacuum can be settled. For some set of parameters the effective potential has several extrema, that in the case of SU(2) I x U(1) Y flavor symmetry can be understood on topological grounds. With increasing strength of the fluctuations the spontaneously broken phase gets unstable and the trivial vacuum is restored. The effective potential reveals furthermore the existence of logarithmic singularities at certain field expectation values, signalizing caustic regions.
Thu, 01 Jan 2004 00:00:00 GMThttps://hdl.handle.net/10316/76972004-01-01T00:00:00ZStationary phase corrections in the process of bosonization of multi-quark interactionshttps://hdl.handle.net/10316/7684Title: Stationary phase corrections in the process of bosonization of multi-quark interactions
Authors: Osipov, A. A.; Hiller, B.; Moreira, J.; Blin, A. H.
Abstract: Abstract The functional integration over the auxiliary bosonic variables of cubic order related with the effective action of the Nambu–Jona–Lasinio model with ’t Hooft term has recently been obtained in the form of a loop expansion. Even numbers of loops contribute to the action, while odd numbers of loops are assigned to the measure. We consider the two-loop corrections and analyse their effect on the low-lying pseudoscalar and scalar mass spectra, quark condensates and weak decay constants. The results are compared to the leading order calculations and other approaches.
Sun, 01 Jan 2006 00:00:00 GMThttps://hdl.handle.net/10316/76842006-01-01T00:00:00ZEffects of eight-quark interactions on the hadronic vacuum and mass spectra of light mesonshttps://hdl.handle.net/10316/4366Title: Effects of eight-quark interactions on the hadronic vacuum and mass spectra of light mesons
Authors: Osipov, A. A.; Hiller, B.; Blin, A. H.; Providência, J. da
Abstract: The combined effective low energy QCD Lagrangians of Nambu-Jona-Lasinio (NJL) and 't Hooft are supplemented with eight-quark interactions. This work is a follow-up of recent findings, namely (i) the six quark flavour determinant 't Hooft term destabilizes the NJL vacuum, (ii) the addition of a chiral invariant eight-fermion contact term renders the ground state of the theory globally stable; (iii) stability constrains the values of coupling constants of the model, meaning that even in the presence of eight-quark forces the system can be unstable in a certain parameter region. In the present work we study a phenomenological output of eight-quark interactions considering the mass spectra of pseudoscalar and scalar mesons. Mixing angles are obtained and their equivalence to the two angle approach is derived. We show that the masses of pseudoscalars are almost neutral to the eight-quark forces. The only marked effect of the second order in the SU(3) breaking is found in the [eta]-[eta]' system. The scalars are more sensitive to the eight-quark interactions. A strong repulsion between the singlet and octet members is the reason for the obtained low mass of the [sigma] state within the model considered.
Mon, 01 Jan 2007 00:00:00 GMThttps://hdl.handle.net/10316/43662007-01-01T00:00:00ZDynamical chiral symmetry breaking by a magnetic field and multi-quark interactionshttps://hdl.handle.net/10316/4370Title: Dynamical chiral symmetry breaking by a magnetic field and multi-quark interactions
Authors: Osipov, A. A.; Hiller, B.; Blin, A. H.; Providência, J. da
Abstract: Catalysis of dynamical symmetry breaking by a constant magnetic field in (3+1) dimensions is considered. We use the three flavour Nambu-Jona-Lasinio type model with 't Hooft and eight-quark interaction terms. It is shown that the multi-quark interactions introduce new additional features to this phenomenon: (a) the local minimum of the effective potential catalyzed by the constant magnetic field is smoothed out with increasing strength of the field at the characteristic scale H~1019 G, (b) the multi-quark forces generate independently another local minimum associated with a larger dynamical fermion mass. This state may exist even for multi-quark interactions with a subcritical set of couplings, and is globally stable with respect to a further increase of the magnetic field.
Mon, 01 Jan 2007 00:00:00 GMThttps://hdl.handle.net/10316/43702007-01-01T00:00:00ZLong distance expansion for the NJL model with SU(3) and UA(1) breakinghttps://hdl.handle.net/10316/4432Title: Long distance expansion for the NJL model with SU(3) and UA(1) breaking
Authors: Osipov, A. A.; Hansen, H.; Hiller, B.
Abstract: This work is a follow up of recent investigations, where we study the implications of a generalized heat kernel expansion, constructed to incorporate non-perturbatively the effects of a non-commutative quark mass matrix in a fully covariant way at each order of the expansion. As underlying Lagrangian we use the Nambu-Jona-Lasinio model of QCD, with SUf(3) and UA(1) breaking, the latter generated by the 't Hooft flavour determinant interaction. The associated bosonized Lagrangian is derived in leading stationary phase approximation (SPA) and up to second order in the generalized heat kernel expansion. Its symmetry breaking pattern is shown to have a complex structure, involving all powers of the mesonic fields allowed by symmetry. The considered Lagrangian yields a reliable playground for the study of the implications of symmetry and vacuum structure on the mesonic spectra, which we evaluate for the scalar and pseudoscalar meson nonets and compare with other approaches and experiment.
Thu, 01 Jan 2004 00:00:00 GMThttps://hdl.handle.net/10316/44322004-01-01T00:00:00ZMulti-quark interactions with a globally stable vacuumhttps://hdl.handle.net/10316/4414Title: Multi-quark interactions with a globally stable vacuum
Authors: Osipov, A. A.; Hiller, B.; Providência, J. da
Abstract: It is shown that U(3)L×U(3)R eight-quark interactions stabilize the asymmetric ground state of the well-known model with four-quark Nambu-Jona-Lasinio and six-quark 't Hooft interactions. The result remains when the reduced SU(3) flavour symmetry is explicitly broken by the general current quark mass term with .
Sun, 01 Jan 2006 00:00:00 GMThttps://hdl.handle.net/10316/44142006-01-01T00:00:00ZLowering the critical temperature with eight-quark interactionshttps://hdl.handle.net/10316/4381Title: Lowering the critical temperature with eight-quark interactions
Authors: Osipov, A. A.; Hiller, B.; Moreira, J.; Blin, A. H.; Providência, J. da
Abstract: It is shown that eight-quark interactions, which are needed to stabilize the ground state of the combined three flavor Nambu-Jona-Lasinio and 't Hooft Lagrangians, play also an important role in determining the critical temperature at which transitions occur from the dynamically broken chiral phase to the symmetric phase.
Mon, 01 Jan 2007 00:00:00 GMThttps://hdl.handle.net/10316/43812007-01-01T00:00:00Z