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Results for "Francesco Giacosa"

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Nuclear matter and chiral phase transition at large-$N_{c}$Jun 02 2011Two aspects of the QCD phase diagrams are studied in the limit of a large number of colors: at zero temperature and nonzero density the (non)existence of nuclear matter, and at zero density and nonzero temperature the chiral phase transition.
Mixing of scalar tetraquark and quarkonia states in a chiral approachNov 30 2006Feb 11 2007A chiral invariant Lagrangian describing the tetraquark-quarkonia interaction is considered at the leading and subleading order in the large-$N_{c}$ expansion. Spontaneous chiral symmetry breaking generates mixing of scalar tetraquark and quarkonia states ... More
Mesons beyond the quark-antiquark pictureNov 14 2015Jan 11 2016The vast majority of mesons can be understood as quark-antiquark states. Yet, various other possibilities exists: glueballs (bound-state of gluons), hybrids (quark-antiquark plus gluon), and four-quark states (either as diquark-antidiquark or molecular ... More
On unitary evolution and collapse in Quantum MechanicsJun 09 2014Dec 09 2014In the framework of an interference setup in which only two outcomes are possible (such as in the case of a Mach-Zehnder interferometer), we discuss in a simple and pedagogical way the difference between a standard, unitary quantum mechanical evolution ... More
Light scalars as tetraquarks: decays and mixing with quarkoniaNov 20 2007Nov 25 2007The tetraquark assignement for light scalar states below 1 GeV is discussed on the light of strong decays. The next-to-leading order in the large-N expansion for the strong decays is considered. Mixing with quarkonia states above 1 GeV is investigated ... More
Spontaneous breaking of chiral symmetry, and eventually of parity, in a $σ$-model with two Mexican hatsJul 21 2009Dec 20 2009A sigma-model with two linked Mexican hats is discussed. This scenario could be realized in low-energy QCD when the ground state and the first excited (pseudo)scalar mesons are included, and where not only in the subspace of the ground states, but also ... More
Dynamical generation and dynamical reconstructionMar 25 2009Dec 06 2009A definition of `dynamical generation', a hotly debated topic at present, is proposed and its implications are discussed. This definition, in turn, leads to a method allowing to distinguish in principle tetraquark and molecular states. The different concept ... More
Non-exponential decay in Quantum Mechanics and Quantum Field TheoryDec 11 2013We describe some salient features as well as some recent developments concerning short-time deviations from the exponential decay law in the context of Quantum Mechanics by using the Lee Hamiltonian approach and Quantum Field Theory by using relativistic ... More
Energy uncertainty of the final state of a decay processMay 20 2013Nov 15 2013We derive the expression for the energy uncertainty of the final state of a decay of an unstable quantum state prepared at the initial time $t=0$. This expression is function of the time $t$ at which a measurement is performed to determine if the state ... More
Non-exponential decay in quantum field theory and in quantum mechanics: the case of two (or more) decay channelsOct 26 2011Jul 01 2012We study the deviations from the exponential decay law, both in quantum field theory (QFT) and quantum mechanics (QM), for an unstable particle which can decay in (at least) two decay channels. After a review of general properties of non-exponential decay ... More
Analytical study of a gas of gluonic quasiparticles at high temperature: effective mass, pressure and trace anomalySep 23 2010May 17 2011The thermodynamical properties of a pure Yang-Mills theory SU(N) is described by a gas of gluonic quasiparticles with temperature dependent mass $m(T)$ and a bag function $B(T).$ The analytic behavior of $m(T)$ and the pressure $p$ at high $T$ are derived ... More
Two-photon decay of a light scalar quark-antiquark stateApr 20 2008The two-photon decay of a light scalar quarkonium is evaluated in a local and a nonlocal approaches. It is shown that the two-photon decay, driven by a triangle quark-loop diagram, is smaller than 1 keV for a mass below 0.7 GeV.
Non-conventional mesons at PANDAFeb 09 2015Non-conventional mesons, such as glueballs and tetraquarks, will be in the focus of the PANDA experiment at the FAIR facility. In this lecture we recall the basic properties of QCD and describe some features of unconventional states.\ We focus on the ... More
Thermal ground state for pure SU(2) Yang-Mills thermodynamicsDec 15 2008Dec 16 2008In this proceeding the emergence of a composite, adjoint-scalar field as an average over (trivial holonomy) calorons and anti-calorons is reviewed. This composite field acts as a background field to the dynamics of perturbative gluons, to which is coupled ... More
Decay law and time dilatationDec 01 2015Apr 16 2016We study the decay law for a moving unstable particle. The usual time-dilatation formula states that the decay width for an unstable state moving with a momentum $p$ and mass $M$ is $\tilde{\Gamma}_{p}=\Gamma M/\sqrt{p^{2}+M^{2}}$ with $\Gamma$ being ... More
f_{2}(1270),$ $a_{1}(1260)$ and $f_{0}(1370)$ as dynamically reconstructed quark-antiquark statesOct 05 2010It is explained why the interpretation of the resonances $f_{2}(1270),$ $a_{1}(1260)$ and $f_{0}(1370)$ as quark-antiquark states is legitimate. The result of the quark model and of recently performed Bethe-Salpeter studies are not (necessarily) in conflict ... More
The eLSM at nonzero densityApr 16 2016The extended Linear Sigma Model (eLSM) is an effective model of QCD which includes in the mesonic sector (pseudo)scalar and (axial-)vector quarkonia mesons as well as one dilaton/glueball field and in the baryonic sector the nucleon doublet and its chiral ... More
Strong and electromagnetic decays of the light scalar mesons interpreted as tetraquark statesMay 17 2006Jul 13 2006The study of two-pseudoscalar and two-photon decays for the scalar meson nonet below 1 GeV is performed within an effective approach in which the scalar resonances are described as (Jaffe's) tetraquark states. The dominant (fall apart decay) and the subdominant ... More
Properties of hadrons in a chiral model with (axial-)vector mesonsNov 21 2011Recent advances in the development of a chiral linear $\sigma$-model with (axial-)vector mesons are presented. The model is based on the basic requirements of global chiral symmetry and dilatation invariance. The role of (axial-)vector states turns out ... More
Two-photon decay of light scalars: a comparison of tetraquark and quarkonium assignmentsDec 02 2007Mar 31 2009Two-photon decays of light scalar mesons are discussed within the quarkonium and tetraquark asignements: in both cases the decay rate of the sigma resonances turns out to be smaller than 1 keV.
Modelling glueballsSep 26 2016Glueballs are predicted in various theoretical approaches of QCD (most notably lattice QCD), but their experimental verification is still missing. In the low-energy sector some promising candidate for the scalar glueball exist, and some (less clear) candidates ... More
A Planck-scale axion and SU(2) Yang-Mills dynamics: Present acceleration and the fate of the photonDec 15 2005Nov 27 2006From the time of CMB decoupling onwards we investigate cosmological evolution subject to a strongly interacting SU(2) gauge theory of Yang-Mills scale $\Lambda\sim 10^{-4}$ eV (masquerading as the $U(1)_{Y}$ factor of the SM at present). The viability ... More
Mirror versus naive assignment in chiral models for the nucleonAug 22 2013Jun 05 2014In the framework of chiral model(s) based on the linear realization of chiral symmetry, we investigate the low-energy phenomenological properties of the nucleon and its chiral partner (identified with either $N(1535)$ or $N(1650)$) in the naive assignment ... More
Non exponential decays of hadronsAug 13 2011We analyze the survival probability of unstable particles in the context of quantum field theory. After introducing the spectral function of resonances, we show that deviations from the exponential decay law occur at short times after the creation of ... More
Decay of light scalar mesons into vector-photon and into pseudoscalar mesonsMay 22 2009The decays of a light scalar meson into a vector meson and a photon ($S\to V\gamma)$ are evaluated in the tetraquark and quarkonium assignments of the scalar states. A link with the radiative decays $\phi\to S\gamma$ is established: experimental results ... More
On the spectral functions of scalar mesonsJul 24 2007Jul 25 2007In this work we study the spectral functions of scalar mesons in one- and two-channel cases. When the propagators satisfy the K\"allen-Lehman representation a normalized spectral function is obtained, allowing to take into account finite-width effects ... More
Does nuclear matter bind at large $N_c$?Feb 16 2011Sep 06 2011The existence of nuclear matter at large $N_{c}$ is investigated in the framework of effective hadronic models of the Walecka type. This issue is strongly related to the nucleon-nucleon attraction in the scalar channel, and thus to the nature of the light ... More
Potential for inert adjoint scalar field in SU(2) Yang-Mills thermodynamicsSep 25 2006Aug 20 2007A scalar adjoint field is introduced as a spatial average over (anti)calorons in a thermalized SU(2) Yang-Mills theory. This field is associated with the thermal ground state in the deconfining phase and acts as a background for gauge fields of trivial ... More
Linear growth of the trace anomaly in Yang-Mills thermodynamicsMar 14 2007Nov 25 2007In the lattice work by Miller [1,2] and in the work by Zwanziger [3] a linear growth of the trace anomaly for high temperatures was found in pure SU(2) and SU(3) Yang-Mills theories. These results show the remarkable property that the corresponding systems ... More
Spectral function of a scalar boson coupled to fermionsOct 15 2012Aug 26 2013We present the calculation of the spectral function of an unstable scalar boson coupled to fermions as resulting from the resummation of the one loop diagrams in the scalar particle self energy. We work with a large but finite high-energy cutoff: in this ... More
Radiative $φ$ decays with derivative interactionsApr 09 2008Oct 14 2008We study the line shapes of radiative $\phi$-decays involving virtual $f_{0}(980)$ and $a_{0}(980)$ mesons which decay, via derivative couplings, to $\pi^{0}\pi^{0}$ and $\pi^{0}\eta$ respectively. After developing the formalism for derivative interactions ... More
Oscillations in the decay law: A possible quantum mechanical explanation of the anomaly in the experiment at the GSI facilityOct 07 2011Jul 16 2012We study the deviations from the usual exponential decay law for quantum mechanical systems. We show that simple and physically motivated deviations from the Breit-Wigner energy distribution of the unstable state are sufficient to generate peculiar deviations ... More
The scalar-isovector sector in the extended Linear Sigma ModelApr 23 2014Aug 20 2014We study basic properties of scalar hadronic resonances within the so-called extended Linear Sigma Model (eLSM), which is an effective model of QCD based on chiral symmetry and dilatation invariance. In particular, we focus on the mass and decay width ... More
The lightest scalar meson in a simple approachMay 12 2013Sep 04 2013We study basic properties of scalar hadronic resonances within a quantum field theoretical toy model. In particular, we focus on the spectral function, the mass and the decay width of the resonance $f_{0}(500)$. In this work, this meson is understood ... More
\(τ\) vector and axial-vector spectral functions in the extended linear sigma modelApr 16 2015The extended linear sigma model describes the vacuum phenomenology of scalar, pseudoscalar, vector and axial-vector mesons at energies \(\simeq 1\text{ GeV}\). We combine the chiral \(U(2)_L\times U(2)_R\) symmetry of this model with a local \(SU(2)_L\times ... More
Bursts of low-energy electron-positron pairs in TeV-range collider physicsJun 23 2008Jun 25 2008In this Letter we investigate the possible emission of low-energy electron neutrinos and electron-positron pairs of anomalously large multiplicity in close-to-central $pp$ collisions at LHC. The scenario is based on confining SU(2) Yang-Mills dynamics ... More
(Oscillating) non-exponential decays of unstable statesApr 09 2012Jul 11 2012We discuss deviations from the exponential decay law which originate when going beyond the Breit-Wigner distribution for an unstable state. In particular, we concentrate on an oscillating behavior, reminiscent of the Rabi-oscillations, in the short-time ... More
A covariant nonlocal Lagrangian for the description of the scalar kaonic sectorJul 06 2016Mesons are extended objects, hence their interaction can be described by utilizing form factors. At the Lagrangian level, one can use nonlocal interaction terms. Here we describe two possible nonlocal Lagrangians leading to a 3D form factor: the first ... More
Resonances f0(1370), f0(1500) and f0(1710) within the extended Linear Sigma ModelDec 05 2013Dec 13 2013In the framework of the extended Linear Sigma Model (eLSM) we investigate the masses and decays of the three scalar-isoscalar resonances $f_{0}(1370)$, $f_{0}(1500)$ and $f_{0}(1710)$. The degrees of freedom of the eLSM are (pseudo)scalars and (axial)vectors ... More
$a_{0}(980)$ as a companion pole of $a_{0}(1450)$Oct 17 2015Jan 28 2016Light scalar hadrons are often understood as dynamically generated resonances. These arise as `companion poles' in the propagators of $q\bar{q}$ seed states when accounting for meson-loop contributions to the self-energies of the latter. Following this ... More
Nonperturbative screening of the Landau poleApr 19 2007Based on the trace anomaly for the energy-momentum tensor, an effective theory for the thermodynamics of the deconfining phase, and by assuming the asymptotic behavior to be determined by one-loop perturbation theory we compute the nonperturbative beta ... More
Phenomenology of pseudotensor mesons and the pseudotensor glueballAug 31 2016We study the decays of the pseudotensor mesons $[ \pi_{2}(1670) , K_{2}(1770) , \eta_{2}(1645) , \eta_{2}(1870) ]$ interpreted as the ground-state nonet of $1^1 D_{2}$ $\bar{q}q$ states using interaction Lagrangians which couple them to pseudoscalar, ... More
Pulsed and continuous measurements of exponentially decaying systemsMay 27 2014We study the influence of a detector on the decay law of a quantum state whose "undisturbed" survival probability is purely exponential. In particular, we consider a detector with a finite energy band of detection, i.e. it interacts only with decay products ... More
Influence of the measurement on the decay law: the bang-bang caseNov 09 2014After reviewing the description of an unstable state in the framework of nonrelativistic Quantum Mechanics (QM) and relativistic Quantum Field Theory (QFT), we consider the effect of pulsed, ideal measurements repeated at equal time intervals on the lifetime ... More
Excited Scalar Mesons and the Search for GlueballsJun 17 2016We discuss the importance of mixing between glueballs -- bound states of gluons -- and excited $\bar{q}q$ states for the glueball search. A preliminary study of the excited states in the Extended Linear Sigma Model (eLSM) suggests their masses in the ... More
Propagator poles and an emergent stable state below threshold: general discussion and the E(38) stateSep 11 2012Mar 27 2013In the framework of a simple quantum field theory describing the decay of a scalar state into two (pseudo)scalar ones we study the pole(s) motion(s) of its propagator: besides the expected pole on the second Riemann sheet, we find -- for a large enough ... More
Deviation from the exponential decay law in relativistic quantum field theory: the example of strongly decaying particlesMay 26 2010Oct 12 2011We show that a short-time regime, in which a deviation from the exponential decay law occurs, exists also in the framework of a superrenormalizable relativistic quantum field theory. This, in turn, implies the possibility of a quantum Zeno effect also ... More
Brief report on `Radiative $φ$ decays with derivative interactions'Dec 17 2008We study the line shapes of radiative $\phi$-decays with a direct coupling of the $\phi$ meson to the $f_{0}(980)$ and $a_{0}(980)$ scalar mesons. The latter couple via derivative interactions to $\pi_0 \pi_0$ and $\pi_0 \eta$, respectively. Although ... More
Anomalies in weak decays of H-like ionsDec 01 2016We investigate the emergence of oscillations in the decay law of unstable systems. We discuss in particular the case of the so-called GSI anomaly seen in the electron capture decays of H-like ions and prove that such oscillations cannot be explained by ... More
Decays of open charmed mesons in the extended Linear Sigma ModelSep 17 2014Nov 09 2014We enlarge the so-called extended linear Sigma model (eLSM) by including the charm quark according to the global $U(4)_r\times U(4)_l$ chiral symmetry. In the eLSM, besides scalar and pseudoscalar mesons, also vector and axial-vector mesons are present. ... More
Thermal contribution of unstable statesFeb 08 2019Within the framework of the Lee model, we analyze in detail the difference between the energy derivative of the phase shift and the standard spectral function of the unstable state. The fact that the model is exactly solvable allows us to demonstrate ... More
Nuclear matter within a dilatation-invariant parity doublet model: the role of the tetraquark at nonzero densityMay 25 2011We investigate the role of a scalar tetraquark state for the description of nuclear matter within the parity doublet model in the mirror assignment. In the dilatation-invariant version of the model a nucleon-nucleon interaction term mediated by the lightest ... More
A model for the very early UniverseJan 02 2008Jan 31 2008A model with N species of massless fermions interacting via (microscopic) gravitational torsion in de Sitter spacetime is investigated in the limit N->infinity. The U_V(N)*U_A(N) flavor symmetry is broken dynamically irrespective of the (positive) value ... More
Large-$N_{c}$ pole trajectories of the vector kaon $K^{\ast}(892) $ and of the scalar kaons $K_{0}^{\ast}(800)$ and $K_{0}^{\ast}(1430)$Apr 06 2016May 17 2016We study the spectral functions, the poles and their trajectories for increasing $N_{c}$ of the vector kaon state $K^{\ast}(892),$ characterized by $I(J^{P})=\frac{1}{2}(1^{-})$, and of the scalar kaons $K_{0}^{\ast}(800)$ and $K_{0}^{\ast}(1430),$ characterized ... More
Chiral density wave in nuclear matterDec 11 2013Dec 19 2014Inspired by recent work on inhomogeneous chiral condensation in cold, dense quark matter within models featuring quark degrees of freedom, we investigate the chiral density-wave solution in nu- clear matter at zero temperature and nonvanishing baryon ... More
Influence of Vector Mesons on the f0(600) Decay Width in a Linear Sigma Model with Global Chiral InvarianceNov 20 2009We consider a globally invariant chiral Lagrangian that contains vector and axial-vector mesons. We compute the f0(600) decay width into two pions and pion-pion scattering lengths and compare with the corresponding results in which the (axial-)vector ... More
Cancellation of the sigma meson in thermal modelsJun 03 2015Sep 14 2015The by now well-established scalar-isoscalar resonance $f_{0}(500)$ (the $\sigma$ meson) seems potentially relevant in the evaluation of thermodynamic quantities of a hadronic gas, since its mass is low. However, we recall that its contribution to isospin-averaged ... More
$K_{0}^{\ast}(800)$ as a companion pole of $K_{0}^{\ast}(1430)$Dec 03 2015Jun 17 2016We study the light scalar sector up to $1.8$ GeV by using a quantum field theoretical approach which includes a single kaonic state in a Lagrangian with both derivative and non-derivative interactions. By performing a fit to $\pi K$ phase shift data in ... More
Gap in the black-body spectrum at low temperatureMar 22 2006Nov 27 2006We postulate that the U(1)$_Y$ factor of the Standard Model is an effective manifestation of SU(2) gauge dynamics being dynamically broken by nonperturbative effects. The modified propagation properties of the photon at low temperatures and momenta are ... More
Meson production in proton-proton scattering within an extended linear sigma modelJun 13 2014We study the production of non-strange mesons in proton-proton scattering reactions within an effective model of mesons and baryons with global chiral symmetry. The model includes the nucleon ($N$) and its chiral partner ($N^{\ast}$) and their couplings ... More
Irrelevance of $f_{0}(500)$ in bulk thermal propertiesMar 24 2016We discuss why the scalar-isoscalar resonance $f_{0}(500)$ should in practice not be included in thermal models describing the freeze-out of heavy-ion collisions. Its contribution into pion multiplicities is in principle relevant because it is light and ... More
The chiral partner of the nucleon in the mirror assignment with global symmetryJan 26 2009We calculate the pion-nucleon scattering lengths $a_{0}^{(\pm)}$ and the mass parameter $m_{0}$, which describes the nucleon mass in the chiral limit, at tree-level in the framework of a globally symmetric linear sigma model with parity-doubled nucleons. ... More
On the two-photon decay width of the sigma mesonOct 17 2007Mar 12 2008We shortly report on the two-photon decay width of the light $\sigma$-meson interpreted as a quarkonium state. Results are given in dependence on the $\sigma$-mass and the constituent mass of the light quark. The triangle quark-loop diagram, responsible ... More
A study of the resonances $K_{0}^{*}(800)$ and $K_{0}^{*}(1430)$Jun 09 2016We study the scalar kaonic states $K_{0}^{\ast}(800)$ and $K_{0}^{\ast}(1430)$ by using a relativistic QFT Lagrangian in which only a single kaonic field corresponding to the well-established scalar state $K_{0}^{\ast}(1430)$ is considered and in which ... More
Radiative corrections to the pressure and the one-loop polarization tensor of massless modes in SU(2) Yang-Mills thermodynamicsMar 09 2006Nov 27 2006We compute the one-loop polarization tensor $\Pi$ for the on-shell, massless mode in a thermalized SU(2) Yang-Mills theory being in its deconfining phase. Postulating that SU(2)$_{\tiny{CMB}}\stackrel{\tiny{today}}=U(1)_Y$, we discuss $\Pi$'s effect on ... More
Is f0(1710) a glueball?Aug 21 2014We study the three-flavor chirally and dilatation invariant extended Linear Sigma Model with (pseudo)scalar and (axial-)vector mesons as well as a scalar dilaton field whose excitations are interpreted as a glueball. The model successfully describes masses ... More
$a_{0}(980)$ revisitedAug 03 2015Jan 11 2016Light scalar hadrons can be understood as dynamically generated resonances. These arise as `companion poles' in the propagators of quark-antiquark seed states when accounting for meson-loop contributions to the self-energies of the latter. Along this ... More
Classical and quantum theory of the massive spin-two fieldAug 01 2015In this paper, we review classical and quantum field theory of massive non-interacting spin-two fields. We derive the equations of motion and Fierz-Pauli constraints via three different methods: the eigenvalue equations for the Casimir invariants of the ... More
Vacuum phenomenology of the chiral partner of the nucleon in a linear sigma model with vector mesonsJul 29 2009Jul 05 2010We investigate a linear sigma model with global chiral $U(2)_{R} \times U(2)_{L}$ symmetry. The mesonic degrees of freedom are the standard scalar and pseudoscalar mesons and the vector and axial-vector mesons. The baryonic degrees of freedom are the ... More
Decay widths of resonances and pion scattering lengths in a globally invariant linear sigma model with vector mesonsDec 11 2008We calculate low-energy meson decay processes and pion-pion scattering lengths in a two-flavour linear sigma model with global chiral symmetry, exploring the scenario in which the scalar mesons $f_0$(600) and $a_0$(980) are assumed to be $\bar q q$ states. ... More
How Universal is the Coupling in the Sigma Model?Apr 24 2008We calculate pion-pion scattering lengths and sigma, rho and a1 decay widths from a gauged linear sigma model with two flavours and its globally invariant generalisation.
Reply to comment on "Two-photon decay of the sigma meson"May 12 2009We reply to the preceding Comment by E. van Beveren et al., arXiv:0811.2589 [hep-ph].
Decays of the vector glueballJul 13 2016We calculate two- and three-body decays of the (lightest) vector glueball into (pseudo)scalar, (axial-)vector, as well as pseudovector and excited vector mesons. By setting the mass of this yet hypothetical vector glueball to 3.8 GeV as predicted by Lattice ... More
Correlation of energy density in deconfining SU(2) Yang-Mills thermodynamicsNov 27 2007Oct 29 2008We compute the two-point correlation of the energy density for the massless mode in deconfining SU(2) Yang-Mills thermodynamics and point towards a possible application for the physics of cold, dilute, and stable clouds of atomic hydrogen within the Milky ... More
Masses of Heavy and Light Scalar Tetraquarks in a Non-Relativistic Quark ModelJul 13 2015Feb 24 2016Scalar tetraquark states are studied within the diquark-antidiquark picture in a non-relativistic approach. We consider two types of confining potentials, a quadratic and a linear one, to which we also add spin-spin, isospin-isospin, and spin-isospin ... More
Structure of Scalar Mesons f(0)(600), a(0)(980), f(0)(1370) and a(0)(1450)Apr 27 2010We calculate low-energy meson decay processes and pion-pion scattering lengths in a globally chirally invariant two-flavour linear sigma model exploring the quark content of the scalar mesons f(0)(600) and a(0)(980), as well as f(0)(1370) and a(0)(1450). ... More
Vacuum Properties of Mesons in a Linear Sigma Model with Vector Mesons and Global Chiral InvarianceMar 25 2010We present a two-flavour linear sigma model with global chiral symmetry and vector and axial-vector mesons. We calculate pion-pion scattering lengths and the decay widths of scalar, vector, and axial-vector mesons. It is demonstrated that vector and axial-vector ... More
Pion-nucleon scattering within a gauged linear sigma model with parity-doubled nucleonsFeb 23 2007We compute pion-nucleon scattering at tree-level within a gauged linear sigma model which contains the nucleon and its chiral partner. Such an investigation in principle allows to make definite predictions as to whether the main contribution to the nucleon ... More
The role of the next-to-leading order triangle-shaped diagram in two-body hadronic decaysJul 28 2014Oct 18 2014The next-to-leading-order contribution to the amplitude of a two-body decay process is a triangle-shaped diagram in which the unstable state is exchanged by the emitted particles. In this work we calculate this diagram in the framework of a scalar quantum ... More
Explosive Z PinchApr 20 2006Nov 08 2006We propose an explanation for the recently observed powerful contained explosion in a Z pinch experiment performed at Sandia National Laboratories. Our arguments are based on the assumption that a pure SU(2) Yang-Mills theory of scale $\sim 0.5 $MeV is ... More
Phenomenology of axial-vector and pseudovector mesons: decays and mixing in the kaonic sectorJun 05 2013Oct 19 2013We study the decays of the lightest axial-vector and pseudovector mesons, interpreted as quark-antiquark states, into a vector and a pseudoscalar meson. We show that the quarkonium assignment delivers a good description of the decays and allows also to ... More
Restoration of chiral symmetry in the large-N_c limitOct 07 2011We study the large-N_c behavior of the critical temperature T_c for chiral symmetry restoration in the framework of the Nambu-Jona-Lasinio (NJL) model and the linear \sigma-model. While in the NJL case T_c scales as N_c^0 and is, as expected, of the same ... More
Study of chiral symmetry restoration in linear and nonlinear O(N) models using the auxiliary field methodAug 09 2011Aug 13 2012We consider the O(N) linear {\sigma} model and introduce an auxiliary field to eliminate the scalar self-interaction. Using a suitable limiting process this model can be continuously transformed into the nonlinear version of the O(N) model. We demonstrate ... More
Role of scalar dibaryon and $f_0(500)$ in the isovector channel of low-energy neutron-proton scatteringMar 14 2016We calculate the total and the differential cross section for $np$ scattering at low energies in the isospin $I=1$ channel within the so-called extended Linear Sigma Model. This model contains conventional (pseudo)scalar and (axial--)vector mesons, as ... More
Inhomogeneous condensation in effective models for QCD using the finite-mode approachAug 25 2015Jan 11 2016We use a numerical method, the finite-mode approach, to study inhomogeneous condensation in effective models for QCD in a general framework. Former limitations of considering a specific ansatz for the spatial dependence of the condensate are overcome. ... More
Light tetraquark state at nonzero temperatureJun 28 2010We study the implications of a light tetraquark on the chiral phase transition at nonzero temperature $T$: The behavior of the chiral and four-quark condensates and the meson masses are studied in the scenario in which the resonance $f_{0}(600)$ is described ... More
Pressure of the O(N) Model in 1+1 DimensionsOct 28 2012The O(N) model in 1+1 dimensions presents some features in common with Yang-Mills theories: asymptotic freedom, trace anomaly, non-petrurbative generation of a mass gap. An analytical approach to determine the termodynamical properties of the O(3) model ... More
Role of the tetraquark in the chiral phase transitionMay 08 2008Mar 24 2009We investigate the implications of a tetraquark field on chiral symmetry restoration at nonzero temperature. In order for the chiral phase transition to be cross-over, as shown by lattice QCD studies, a strong mixing between scalar quarkonium and tetraquark ... More
Phenomenology of charmed mesons in the extended Linear Sigma ModelMay 05 2014Sep 22 2015We study the so-called extended linear sigma model for the case of four quark flavors. This model is based on global chiral symmetry and dilatation invariance and includes, besides scalar and pseudoscalar mesons, vector and axial-vector mesons. Most of ... More
A Three-Flavor Chiral Effective Model with Four Baryonic Multiplets within the Mirror AssignmentNov 16 2015Feb 15 2016In the case of three quark flavors, (pseudo)scalar diquarks transform as antiquarks under chiral transformations. We construct four spin-1/2 baryonic multiplets from left- and right-handed quarks as well as left- and right-handed diquarks. The fact that ... More
The Glueball in a Chiral Linear Sigma Model with Vector MesonsMar 16 2011We present a two-flavour linear sigma model with global chiral symmetry and (axial-)vector mesons as well as an additional glueball degree of freedom. We study the structure of the well-established scalar resonances f0(1370) and f0(1500): by a fit to ... More
Lattice versus 2PI: 2d O(N) model at nonzero TOct 17 2012The thermodynamics of the O(N) model in 1+1 dimensions is studied applying the CJT formalism and the auxiliary field method as well as fully nonperturbative finite temperature lattice simulations. The numerical results for the renormalized mass of the ... More
Black-Body Anomaly: Analysis of Temperature OffsetsJul 20 2007Based on the postulate that photon propagation is governed by a dynamically broken SU(2) gauge symmetry (scale $\sim 10^{-4} $eV) we make predictions for temperature offsets due to a low-temperature (a few times the present CMB temperature) spectral anomaly ... More
The O(2) model in polar coordinates at nonzero temperatureOct 12 2011May 11 2013We study the restoration of spontaneously broken symmetry at nonzero temperature in the framework of the O(2) model using polar coordinates. We apply the CJT formalism to calculate the masses and the condensate in the double-bubble approximation, both ... More
Thermodynamics of the O(3) model in 1+1 dimensions: lattice vs. analytical resultsSep 19 2012Jul 01 2013A detailed study of the thermodynamics of the O(N=3) model in 1+1 dimensions is presented, employing a two-particle-irreducible resummation prescription as well as fully nonperturbative finite-temperature lattice simulations. The analytical results are ... More
Spatial Wilson loop in continuum, deconfining SU(2) Yang-Mills thermodynamicsDec 10 2008Dec 09 2009The uniquess of the effective actions describing 4D SU(2) and SU(3) continuum, infinite-volume Yang-Mills thermodynamics in their deconfining and preconfining phases is made explicit. Subsequently, the spatial string tension is computed in the approach ... More
Masses of Axial-Vector Resonances in a Linear Sigma Model with Nf=3Nov 28 2010We discuss an Nf=3 linear sigma model with vector and axial-vector mesons (extended Linear Sigma Model - eLSM). We present first results regarding the masses of axial-vector mesons determined from the extended model.
Role of scalar dibaryon and $f_0(500)$ in the isovector channel of low-energy neutron-proton scatteringMar 14 2016Nov 17 2016We calculate the total and the differential cross section for $np$ scattering at low energies in the isospin $I=1$ channel within the so-called extended Linear Sigma Model. This model contains conventional (pseudo)scalar and (axial--)vector mesons, as ... More
Decay of the pseudoscalar glueball into scalar and pseudoscalar mesonsAug 31 2012Apr 29 2013We study a chiral Lagrangian which describes the two- and three-body decays of a pseudoscalar glueball into scalar and pseudoscalar mesons. The various branching ratios are a parameter-free prediction of our approach. We compute the decay channels for ... More
Low-energy limit of the extended Linear Sigma ModelMay 17 2016The extended Linear Sigma Model (eLSM) is an effective hadronic model based on the linear realization of chiral symmetry $SU(N_f)_L \times SU(N_f)_R$, with (pseudo)scalar and (axial-)vector mesons as degrees of freedom. In this paper, we study the low-energy ... More