NOTAS DE FÍSICA

Nonlocality Effect in Alpha Decay of Heavy and Superheavy Nuclei

Emil L. Medeiros, N. Teruya, Sérgio B. Duarte, O. A. P. Tavares — Sun, 10 Apr 2022 00:00:00 -0300

Alpha decay half-life of heavy and superheavy nuclei has been investigated using a potential barrier penetration model that adapts semiclassical WKB calculations to incorporate a coordinate-dependent effective mass for the alpha particle. This effect is a consequence of a dynamic property of nonlocality in the particle-nucleus interaction, as implemented in the barrier tunneling calculations of Ref. [1]. Calculations have been performed for a recent set of experimental data of 255 alpha-emitting nuclides, all selected with angular momentum $\ell = 0$ experimentally assigned. Results show a good agreement when compared to experimental half-life data, obtaining a standard deviation $\sigma=0.306$, and fully satisfying the universal NUP and UDL systematics of alpha decay. Additionally, the present model has been applied to make half-life predictions for thirty-four possible, new alpha decay cases.

The Periodic Table of the Elements

Maria Terranova, Odilon A. P. Tavares — Sun, 10 Apr 2022 00:00:00 -0300

The Periodic Table of Mendeleev, initially proposed on the basis of 66 elements, and containing 82 elements at the time of Moseley (1887−1915), describes nowadays 118 elements. The huge challenge of this scientific adventure was, and still is, the development of technologies and methods capable of producing elements of atomic number Z > 103, known as superheavy elements (SHE), or transactinides. This paper presents a survey of experiments and theoretical approaches that led physicists and chemists of today to discover and characterize a number of SHE isotopes. A glance is also given to the feasibility studies performed by scientists aiming to going beyond Z = 118, building-up further neutron-rich nuclides and reaching the ultimate goal of creating long-living new elements at the edge of the Table.

First quantization of braided Majorana fermions

Francesco Toppan — Sun, 10 Apr 2022 00:00:00 -0300

A Z2-graded qubit represents an even (bosonic) “vacuum state” and an odd, excited,
Majorana fermion state. The multiparticle sectors of N, braided, indistinguishable Majorana fermions are constructed via first quantization. The framework is that of a graded
Hopf algebra endowed with a braided tensor product. The Hopf algebra is U(gl(1|1)), the
Universal Enveloping Algebra of the gl(1|1) superalgebra. A 4×4 braiding matrix Bt defines
the braided tensor product. Bt, which is related to the R-matrix of the Alexander-Conway
polynomial, depends on the braiding parameter t belonging to the punctured plane (t ∈ C
∗
);
the ordinary antisymmetry property of fermions is recovered for t = 1.
For each N, the graded dimension m|n of the graded multiparticle Hilbert space is computed.
Besides the generic case, truncations occur when t coincides with certain roots of unity which
appear as solutions of an ordered set of polynomial equations. The roots of unity are organized into levels which specify the maximal number of allowed braided Majorana fermions
in a multiparticle sector.
By taking into account that the even/odd sectors in a Z2-graded Hilbert space are superselected, a nontrivial braiding with t 6= 1 is essential to produce a nontrivial Hilbert space
described by qubits, qutrits, etc., since at t = 1 the N-particle vacuum and the antisymmetrized excited state encode the same information carried by a classical $1$-bit.