Multifractal analysis of nonhyperbolic coupled map lattices: Application to genomic sequences

Symbolic sequences generated by coupled map lattices (CMLs) can be used to model the chaotic-like structure of genomic sequences. In this study it is shown that diffusively coupled Chebyshev maps of order 4 (corresponding to a shift of 4 symbols) very closely reproduce the multifractal spectrum $D_q$ of human genomic sequences for coupling constant $\alpha =0.35\pm 0.01$ if $q>0$. The presence of rare configurations causes deviations for $q<0$, which disappear if the rare event statistics of the CML is modified. Such rare configurations are known to play specific functional roles in genomic sequences serving as promoters or regulatory elements.Comment: 7 pages, 6 picture

An uncombed inversion of multi-wavelength observations reproducing the Net Circular Polarization in a sunspots' penumbra

I derived a geometrical model of the penumbral magnetic field topology from an uncombed inversion setup that aimed at reproducing the NCP of simultaneous spectra in near-IR (1.56 mu) and VIS (630 nm) spectral lines. I inverted the spectra of five photospheric lines with a model that mimicked vertically interlaced magnetic fields with two components, labeled background field and flow channels. The flow channels were modeled as a perturbation of the background field with a Gaussian shape using the SIRGAUS code. The location and extension of the Gaussian perturbation in the optical depth scale was then converted to a geometrical height scale. I investigated the relative amount of magnetic flux in the flow channels and the background field atmosphere. The uncombed model is able to reproduce the NCP well on the limb side of the spot and worse on the center side; the VIS lines are better reproduced than the near-IR lines. The Evershed flow happens along nearly horizontal field lines close to the solar surface. The magnetic flux that is related to the flow channels makes up about 20-50% of the total magnetic flux in the penumbra. The gradients obtainable by a Gaussian perturbation are too small for a perfect reproduction of the NCP in the IR lines with their small formation height range. Two peculiarities of the observed NCP, a sign change of the NCP of the VIS lines on the center side and a ring structure around the umbra in the Ti line at 630.37nm and the FeI line at 1565.2nm deserve closer attention. The large fraction of magnetic flux related to the flow channel component could allow to replenish the penumbral radiative losses in the flux tube picture.Comment: 12 pages, 14 figures + 4 pages Appendix, 5 figures, accepted by Astronomy & Astrophysic

Molecular resonance phenomena and alpha-clustering: recent progress and perspectives

The connection between molecular resonance phenomena in light heavy-ion collisions, alpha-clustering and extremely deformed states in light $\alpha$-like nuclei is discussed. For example, the superdeformed bands recently discovered in light N=Z nuclei such as $^{36}$Ar, $^{40}$Ca, $^{48}$Cr, and $^{56}$Ni by $\gamma$-ray spectroscopy may have a special link with resonant states in collisions with $\alpha$-like nuclei. The resonant reactions involving identical bosons such as $^{12}$C+$^{12}$C, $^{16}$O+$^{16}$O $^{24}$Mg+$^{24}$Mg and $^{28}$Si+$^{28}$Si are of interest. For instance, a butterfly mode of vibration of the J$^{\pi}$ = 38$^{+}$ resonance of $^{28}$Si+$^{28}$Si has been discovered in recent particle $\gamma$-ray angular correlations measurements. The search for signatures of strongly deformed shapes and clustering in light N=Z nuclei is also the domain of charged particle spectroscopy. The investigation of $\gamma$-decays in $^{24}$Mg has been undertaken for excitation energies where previously nuclear molecular resonances were found in $^{12}$C+$^{12}$C collisions. In this case the $^{12}$C-$^{12}$C scattering states can be related to the breakup resonance and, tentatively, to the resonant radiative capture $^{12}$C+$^{12}$C reaction.Comment: 7 pages, 3 figures included. Invited Talk 8th Int. Conf. on Clustering Aspects of Nuclear Structure and Dynamics, Nara, Japan, Nov. 24-29, 2003; To be published in Nucl. Phys.

Molecular structures and clustering effects in reactions induced by light nuclei

$\alpha$-clustering study since the pioneering discovery of $^{12}$C+$^{12}$C molecular resonances half a century ago. Our knowledge on physics of nuclear molecules has increased considerably and nuclear clustering remains one of the most fruitful domains of nuclear physics, facing some of the greatest challenges and opportunities in the years ahead. The occurrence of "exotic" shapes in light $N$=$Z$ $\alpha$-like nuclei is investigated. Various approaches of the superdeformed and hyperdeformed bands associated with quasimolecular resonant structures are presented. Evolution of clustering from stability to the drip-lines is examined: clustering aspects are, in particular, discussed for light exotic nuclei with large neutron excess such as neutron-rich Oxygen isotopes with their complete spectrocopy.Comment: 16 pages, 7 figures, Invited Talk presented at the First International African Symposium on Exotic Nuclei IASEN2013 Ithemba LABS Cape Town, South Africa, December 2-6, 2013; Proceedings to be published by World Scientifi

Competition between quasi-molecular resonances and fusion-fission in light dinuclear systems

The results presented in this paper clearly suggest that a coherent framework may exist which connects the topics of heavy-ion molecular resonances, hyperdeformation effects, and fission shape isomerism. New data on particle-particle-$\gamma$ triple coincidences of the $^{28}$Si+$^{28}$Si reaction at a beam energy corresponding to the population of a conjectured J$^{\pi}$ = 38$^{+}$ resonance in $^{56}$Ni are presented. The absence of alignment of the spins of the outgoing fragments with respect to the orbital angular momentum is found to be in contrast with the alignment as measured for the $^{24}$Mg+$^{24}$Mg resonances. A molecular-model picture is presented to suggest a "butterfly" motion of two oblate $^{28}$Si nuclei interacting in a equator-to-equator molecular configuration.Comment: 10 pages standard REVTeX file, 7 ps and eps Figures included -- Talk given at the International Conference ``Nuclear Physics close to the Barrier", Warsaw, Poland, June 30- July 4, 1998 (Proceedings to be published in Acta Physica Polonica A, fall 1998) -