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C. L. Lima

Publications and source records attributed to C. L. Lima.

12 recordsLinked to original sources
arXiv2013

Low-temperature Raman spectra of L-histidine crystal

We present a Raman spectroscopy investigation of the vibrational properties of L-histidine crystals at low temperatures. The temperature dependence of the spectra show discontinuities at 165 K, which we identify with modifications in the bonds associated to both the NH3+ and CO2- motifs indicative of a conformational phase transition that changes the intermolecular bonds. Additional evidence of such a phase transition was provided by differential scanning calorimetry measurements, which identified an enthalpic anomaly at ~165 K.

physics.chem-ph↗
arXiv2007

Effective interactions from q-deformed inspired transformations

From the mass term for the transformed quark fields, we obtain effective contact interactions of the NJL type. The parameters of the model that maps a system of non-interacting transformed fields into quarks interacting via NJL contact terms are discussed.

nucl-th↗
arXiv2007

Quantum spin tunneling of magnetization in small ferromagnetic particles

A new quantum approach is presented that can account for the description of small ferromagnetic particles magnetization tunneling. An estimate of the saturation value of an external applied magnetic field along the easy axis is obtained. An analytic expression for the tunneling factor in the absence of an external magnetic field is deduced from the present approach that also allows to obtain the crossover temperature characterizing the regime where tunneling is dominated by the quantum effects.

cond-mat.mes-hall↗
arXiv2004

Quantum spin tunneling in a soluble quasi-spin model: An angle-based potential description

We propose an approach which allows to construct and use a potential function written in terms of an angle variable to describe interacting spin systems. We show how this can be implemented in the Lipkin-Meshkov-Glick, here considered a paradigmatic spin model. It is shown how some features of the energy gap can be interpreted in terms of a spin tunneling. A discrete Wigner function is constructed for a symmetric combination of two states of the model and its time evolution is obtained. The physical information extracted from that function reinforces our description of phase oscillations in a potential.

quant-ph↗
arXiv2001

Mass formula for T=0 and T=1 ground states of N=Z nuclei

An algebraic model is developed to calculate the T=0 and T=1 ground state binding energies for N=Z nuclei. The method is tested in the sd shell and is then extended to 28-50 shell which is currently the object of many experimental studies.

nucl-th↗
arXiv2001

11Li stability and its single particle structure

The stability of the 11Li exotic nucleus is discussed focusing on the existence of single particle positive energy components in its ground state structure. The existence of these continuum components is an outcome of many models using the available experimental data of 10Li. We show that if this were the case, the 11Li main decay mode could not be the beta decay.

nucl-th↗
arXiv1999

On the q-deformation of the NJL model

Using a q-deformed fermionic algebra we perform explicitly a deformation of the Nambu-Jona-Lasinio (NJL) Hamiltonian. In the Bogoliubov-Valatin approach we obtain the deformed version of the functional for the total energy, which is minimized to obtain the corresponding gap equation. The breaking of chiral symmetry and its restoration in the limit $q \to 0$ are then discussed.

nucl-th↗
arXiv1999

Effect of q-deformation in the NJL gap equation

We obtain a q-deformed algebra version of the Nambu-Jona-Lasinio model gap equation. In this framework we discuss some hadronic properties such as the dynamical mass generated for the quarks, the pion decay constant and the phase transition present in this model.

nucl-th↗
arXiv1998

Peripheral N$α$ Scattering: A Tool For Identifying The Two Pion Exchange Component Of The NN Potential

We study elastic N$α$ scattering and produce a quantitative correlation between the range of the effective potential and the energy of the system. This allows the identification of the waves and energies for which the scattering may be said to be peripheral. We then show that the corresponding phase shifts are sensitive to the tail of the NN potential, which is due to the exchange of two pions. However, the present uncertainties in the experimental phase shifts prevent the use of N$α$ scattering to discriminate the existing models for the NN interaction.

nucl-th↗
arXiv1995

Unitary operator bases and q-deformed algebras

Starting from the Schwinger unitary operator bases formalism constructed out of a finite dimensional state space, the well-known q-deformed commutation relation is shown to emerge in a natural way, when the deformation parameter is a root of unity.

q-alg↗
arXiv1993

Deformed Gaussian Orthogonal Ensemble Analysis of the Interacting Boson Model

A Deformed Gaussian Orthogonal Ensemble (DGOE) which interpolates between the Gaussian Orthogonal Ensemble and a Poissonian Ensemble is constructed. This new ensemble is then applied to the analysis of the chaotic properties of the low lying collective states of nuclei described by the Interacting Boson Model (IBM). This model undergoes a transition order-chaos-order from the $SU(3)$ limit to the $O(6)$ limit. Our analysis shows that the quantum fluctuations of the IBM Hamiltonian, both of the spectrum and the eigenvectors, follow the expected behaviour predicted by the DGOE when one goes from one limit to the other.

nucl-th↗