Chiral Soliton Model Research Articles

Simulation of time-crystal-like behavior for a few-boson chiral soliton model in a ring

We present numerical simulations for a chiral soliton model with N=2,3 bosons in a ring, which is a few-particle version of our previous mean-field model for a quantum time crystal. Following Syrwid, Kosior, and Sacha (SKS), the notion is that a precise position measurement of one particle can lead to spontaneous formation of a bright soliton that in a time crystal should rotate intact for at least a few revolutions around the ring. In their work SKS found spontaneous formation of a soliton due to the position measurement, but quantum fluctuations cause the soliton to subsequently decay before it has a chance to perform even one revolution of the ring. Based on this, they concluded that time-crystal dynamics are impossible for Wilczek's model of a bright soliton in a ring. In contrast, for our few-boson chiral soliton model, allowing for imprecise (weak) measurements of the particle position, we show that time-crystal-like behavior is possible, allowing for several revolutions of the spontaneously formed soliton around the ring. Published by the American Physical Society 2024

Doubly heavy tetraquarks in the chiral quark soliton model

The chiral quark soliton model has been successfully applied to describe the heavy baryon spectrum, both for charm and bottom, leading to the conclusion that the heavy quark has no effect on the soliton. This suggests that replacing a heavy quark by a heavy antidiquark $\overline{Q}\overline{Q}$ in color triplet should give a viable description of heavy tetraquarks. We follow this strategy to compute tetraquark masses. To estimate heavy diquark masses, we use the Cornell potential with appropriately rescaled parameters. The lightest charm tetraquark is 70 MeV above the $D{D}^{*}$ threshold. On the contrary, both nonstrange and strange bottom tetraquarks are bound by approximately 140 and 60 MeV, respectively.

Singly heavy baryons in nuclear matter from an SU(3) chiral soliton model

We investigate how the masses of singly heavy baryons undergo changes in nuclear matter, based on a medium-modified SU(3) chiral soliton model. Having explained the bulk properties of nuclear matter, we discuss the masses of singly heavy baryons in nuclear matter. We generalize the vector-meson Lagrangian including the heavy-meson soliton interaction. The mass spectrum of singly heavy baryons are obtained with the effects of explicit SU(3) symmetry breaking considered as a perturbation. The results show that the mass of the singly heavy baryon in a nuclear medium is rather sensitive to the medium modifications of the heavy meson mass.

Baryonic matter and the medium modification of the baryon masses

We investigate the properties of baryonic matter within the framework of the in-medium modified chiral soliton model by taking into account the effects of surrounding baryonic environment on the properties of in-medium baryons. The internal parameters of the model are determined based on nuclear phenomenology at nonstrange sector and fitted by reproducing nuclear matter properties near the saturation point. We discuss the equations of state in different nuclear environments such as symmetric nuclear matter, neutron and strange matters. We show that the results for the equations of state are in good agreement with the phenomenology of nuclear matter. We also discuss how the SU(3) baryons masses undergo changes in these various types of nuclear matter.

Chiral Soliton Models and Nucleon Structure Functions

We outline and review the computations of polarized and unpolarized nucleon structure functions within the bosonized Nambu-Jona-Lasinio chiral soliton model. We focus on a consistent regularization prescription for the Dirac sea contribution and present numerical results from that formulation. We also reflect on previous calculations on quark distributions in chiral quark soliton models and attempt to put them into perspective.

Lack of a genuine time crystal in a chiral soliton model

In a recent publication [Phys. Rev. Lett. {\bf 124}, 178902] \"Ohberg and Wright claim that in a chiral soliton model it is possible to realize a genuine time crystal which corresponds to a periodic evolution of an inhomogeneous probability density in the lowest energy state. We show that this result is incorrect and present a solution which possesses lower energy with the corresponding probability density that does not reveal any motion. It implies that the authors' conclusion that a genuine time crystal can exist in the system they consider is not true.

Nucleon quasi-parton distributions in the large Nc limit

In this letter, we investigate the nucleon quasi-parton distribution functions in the chiral quark soliton model. We derive a set of sum-rules depending on the velocity of the nucleon and on the Dirac matrix defining the distribution functions. We present numerical results for the isosinglet unpolarized distribution, in which we find that the anti-quark distribution breaks the positivity condition at nucleon velocities of v≈0.99(PN≈7.0MN) and smaller. We found that, for the isosinglet unpolarized case, a large nucleon momentum is required for the quasi-parton distribution to get close enough to the usual parton distribution function.

Nucleon structure functions from the NJL-model chiral soliton

We present numerical simulations for unpolarized and polarized structure functions in a chiral soliton model. The soliton is constructed self-consistently from quark fields from which the structure functions are extracted. Central to the project is regularizing the Dirac sea (or vacuum) contribution to structure functions directly from the regularized action functional that defines the model. In turn, the structure functions are obtained from matrix elements of symmetry currents without assumptions on the nature of quark bilocal and bilinear operators. We discuss in detail how sum rules are realized at the level of the quark wave-functions in momentum space. The comparison with experimental data is convincing for the polarized structure functions but exhibits some discrepancies in the unpolarized case. The vacuum contribution to the polarized structure functions is particularly small.

Exotic Baryons in Chiral Soliton Models

We cautiously review the treatment of pentaquark exotic baryons in chiral soliton models. We consider two examples and argue that any consistent and self-contained description must go beyond the mean field approximation that only considers the classical soliton and the canonical quantization of its (would-be) zero modes via collective coordinates.

Nucleons in Nuclear Matter and Properties of Nuclei

In this contribution we discuss the properties of nucleons and atomic nuclei in the framework of in-medium modified chiral soliton model. The mesonic Lagrangian of the model takes into account an influence of surrounding nuclear environment to the nucleon properties. The model correctly describes the Equations of State of isospin-symmetric and isospin-asymmetric nuclear matter near the nuclear saturation density ρ0. An extrapolation of the results to high density region allows to describe the properties of neutron stars. The model also can be applied to analysis of the properties of mirror nuclei.

Tensor form factors of the octet hyperons in QCD

Light-cone QCD sum rules to leading order in QCD are used to investigate the tensor form factors of the $\Sigma-\Sigma$, $\Xi-\Xi$ and $ \Sigma-\Lambda$ transitions in the range $1 GeV^2 \leq Q^2 \leq 10 GeV^2$. The DAs of $\Sigma$, $\Xi$ and $\Lambda$ baryon have been calculated without higher order terms. Then, study including higher order corrections have been done for $\Sigma$ and $\Lambda$ baryon. The result of form factors are obtained using these two DAs. We make a comparison with the predictions of the chiral quark soliton model.

LHCb pentaquarks as a baryon-ψ(2S)bound state: Prediction of isospin-32pentaquarks with hidden charm

The pentaquark $P_c^+(4450)$ recently discovered by LHCb has been interpreted as a bound state of $\Psi(2S)$ and nucleon. The charmonium-nucleon interaction which provides the binding mechanism is given, in the heavy quark limit, in terms of charmonium chromoelectric polarizabilities and densities of the nucleon energy-momentum tensor (EMT). In this work we show in model-independent way, by exploring general properties of the effective interaction, that $\Psi(2S)$ can form bound states with nucleon and $\Delta$. Using the Skyrme model to evaluate the effective interaction in the large-$N_c$ limit and estimate $1/N_c$ corrections, we confirm the results from prior work which were based on a different effective model (chiral quark soliton model). This shows that the interpretation of $P_c^+(4450)$ is remarkably robust and weakly dependent on the details of the effective theories for the nucleon EMT. We explore the formalism further and present robust predictions of isospin $\frac32$ bound states of $\Psi(2S)$ and $\Delta$ with masses around $4.5\,{\rm GeV}$ and widths around $70\,{\rm MeV}$. The approach also predicts broader resonances in the $\Psi(2S)$-$\Delta$ channel at $4.9\,{\rm GeV}$ with widths of the order of $150\,{\rm MeV}$. We discuss in which reactions these new isospin $\frac 32$ pentaquarks with hidden charm can be observed.

Simple estimates of the masses of pentaquarks with hidden beauty or strangeness

The masses of cryptoexotic pentaquarks with hidden beauty are estimated phenomenologically using the results by the LHCb collaboration which discovered recently the cryptoexotic pentaquarks with hidden charm. The expected masses of the hidden beauty pentaquarks are about $10.8$ GeV and $10.7$ GeV in the limit of some kind of heavy quark symmetry. The states with hidden strangeness considered in similar way have masses about $2.37$ Gev and $2.30$ GeV, by several hundreds of MeV higher than states discussed previously in connection with the relatively light positive strangeness pentaquark $\theta^+$. Empirical data on spectra of pentaquarks can be used to get information about quarkonia interaction with nucleons. The results obtained for the case of heavy flavors are in fair agreement with model of isospin (pion) exchange between flavored baryons and anti-flavored vector mesons, proposed by Karliner and Rosner, and in qualitative agreement with the bound state version of the chiral soliton model.

Hyperon semileptonic decay constants with flavor SU(3) symmetry breaking

We investigate the hyperon semileptonic decay constants, $f_2/f_1$, and $g_1/f_1$, within a general framework of a chiral soliton model. All relevant parameters for the SU(3) baryon wave functions were unambiguously determined by using the experimental data for the masses of the baryon octet and the decuplet. Using then the existing experimental data for the magnetic moments of the baryon octet and the decay constants of hyperon semileptonic decays, we are able to determine all the hyperon semileptonic decay constants $f_2/f_1$ and $g_1/f_1$ of the baryon octet unequivocally. In addition, we also present the results of the axial-vector transition constants from the baryon decuplet to the octet.

Heavy baryons with strangeness in a soliton model

We present results from a chiral soliton model calculation for the spectrum of baryons with a single heavy quark (charm or bottom) and non-zero strangeness. We treat the strange components within a three flavor collective coordinate quantization of the soliton that fully accounts for light flavor symmetry breaking. Heavy baryons emerge by binding a heavy meson to the soliton. The dynamics of this heavy meson is described by the heavy quark effective theory with finite mass effects included.

Neutron star structure in an in-medium modified chiral soliton model

We study the internal structure of a static and spherically symmetric neutron star in the framework of an in-medium modified chiral soliton model. The Equations of State describing an infinite and asymmetric nuclear matter are obtained introducing the density dependent functions into the low energy free space Lagrangian of the model starting from the phenomenology of pionic atoms. The parametrizations of density dependent functions are related to the properties of isospin asymmetric nuclear systems at saturation density of symmetric nuclear matter ρ0≃0.16 fm−3. Our results, corresponding to the compressibility of symmetric nuclear matter in the range 250 MeV≤K0≤270 MeV and the slop parameter value of symmetry energy in the range 30 MeV≤LS≤50 MeV, are consistent with the results from other approaches and with the experimental indications. Using the modified Equations of State, near the saturation density of symmetric nuclear matter ρ0, the extrapolations to the high density and highly isospin asymmetric regions have been performed. The calculations showed that the properties of ∼1.4M⊙ and ∼2M⊙ neutron stars can be well reproduced in the framework of present approach.

The baryon mass calculation in the chiral soliton model at finite temperature and density

In the mean-field approximation, we have studied the soliton which is embedded in a thermal medium within the chiral soliton model. The energy of the soliton or the baryon mass in the thermal medium has been carefully evaluated, in which we emphasize that the thermal effective potential in the soliton energy should be properly treated in order to derive a finite and well-defined baryon mass out of the thermal background. The result of the baryon mass at finite temperatures and densities in chiral soliton model are clearly presented.

Flavor structure of the unpolarized and longitudinally polarized sea-quark distributions in the nucleon

It is now widely recognized that a key to unravel the nonperturbative chiral-dynamics of QCD hidden in the deep-inelastic-scattering observables is the flavor structure of sea-quark distributions in the nucleon. We analyze the flavor structure of the nucleon sea in both of the unpolarized and longitudinally polarized parton distribution functions (PDFs) within a single theoretical framework of the flavor SU(3) chiral quark soliton model (CQSM), which contains only one adjustable parameter $\Delta m_s$, the effective mass difference between the strange and nonstrange quarks. A particular attention is paid to a nontrivial correlation between the flavor asymmetry of the unpolarized and longitudinally polarized sea-quark distributions and also to a possible particle-antiparticle asymmetry of the strange quark distributions in the nucleon. We also investigate the charge-symmetry-violation (CSV) effects in the parton distribution functions exactly within the same theretical framework, which is expected to provide us with valuable information on the relative importance of the asymmetry of the strange and antistrange distributions and the CSV effects in the valence-quark distributions inside the nucleon in the resolution scenario of the so-called NuTeV anomaly in the extraction of the Weinberg angle.

Energy–momentum tensor form factors of the nucleon within a π–ρ–ω soliton model

We investigate the energy–momentum tensor form factors (FFs) of the nucleon within the framework of a chiral soliton model, including the ρ and ω vector mesons. We examine the role of each meson degrees of freedom in these FFs. It is explicitly shown that the pion provides strong attraction whereas the ρ and ω yield repulsion in such a way that the soliton becomes stabilized. The results are discussed in comparison with those of other models.

Studying the baryon properties through chiral soliton model at finite temperature and density

We have studied the chiral soliton model in a thermal vacuum. The soliton equations are solved at finite temperature and density. The temperature or density dependent soliton solutions are presented. The physical properties of baryons are derived from the soliton solutions at finite temperature and density. The temperature or density dependent variation of the baryon properties are discussed.