Searcharxiv⌕ Search

arXiv subjects

S. De Leo

Publications and source records attributed to S. De Leo.

At least 19 recordsLinked to original sources
arXiv2019

Experimental evidence of laser power oscillations induced by the relative Fresnel (Goos-Haenchen) phase

The amplification of the relative Fresnel (Goos-Haenchen) phase by an appropriate number of total internal reflections and the choice of favorable incidence angles allow to observe full oscillations in the power of a DPSS laser transmitted through sequential BK7 blocks. The experimental results confirm the theoretical predictions. The optical apparatus used in this letter can be seen as a new type of two-phase ellipsometric system where the phase of the complex refractive index is replaced by the relative Fresnel (Goos-Haenchen) phase.

physics.optics↗
arXiv2009

Potential Scattering in Dirac Field Theory

We develop the potential scattering of a spinor within the context of perturbation field theory. As an application, we reproduce, up to second order in the potential, the diffusion results for a potential barrier of quantum mechanics. An immediate consequence is a simple generalization to arbitrary potential forms, a feature not possible in quantum mechanics.

hep-th↗
arXiv2004

Quaternionic commutations

Given n quaternions we investigate the extent of non-commutativity of their multiple products, commutators and exponential products.

math.RA↗
arXiv2004

Above potential barrier diffusion

The stationary phase method is applied to diffusion by a potential barrier for an incoming wave packet with energies greater then the barrier height. It is observed that a direct application leads to paradoxical results. The correct solution, confirmed by numerical calculations is the creation of multiple peaks as a consequence of multiple reflections. Lessons concerning the use of the stationary phase method are drawn.

quant-ph↗
arXiv2004

Wave packets and quantum oscillations

We give a detailed analysis of the oscillation formula within the context of the wave packet formalism. Particular attention is made to insure flavor eigenstate creation in the physical cases (Delta p not equal 0). This requirement imposes non instantaneous particle creation in all frames. It is shown that the standard formula is not only exact when the mass wave packets have the same velocity, but it is a good approximation when minimal slippage occurs. For more general situations the oscillation formula contains additional arbitrary parameters, which allows for the unknown form of the wave packet envelope.

hep-ph↗
arXiv2004

Survival law in a potential model

The radial equation of a simple potential model has long been known to yield an exponential decay law in lowest order (Breit-Wigner) approximation. We demonstrate that if the calculation is extended to fourth order the decay law exhibits the quantum Zeno effect. This model has further been studied numerically to characterize the extra exponential time parameter which compliments the lifetime. We also investigate the inverse Zeno effect.

quant-ph↗
arXiv2004

Amplification of coupling for Yukawa potentials

It is well known that Yukawa potentials permit bound states in the Schrodinger equation only if the ratio of the exchanged mass to bound mass is below a critical multiple of the coupling constant. However, arguments suggested by the Darwin term imply a more complex situation. By numerically studying the Dirac equation with a Yukawa potential we investigate this amplification effect.

hep-th↗
arXiv2003

Solving simple quaternionic differential equations

The renewed interest in investigating quaternionic quantum mechanics, in particular tunneling effects, and the recent results on quaternionic differential operators motivate the study of resolution methods for quaternionic differential equations. In this paper, by using the real matrix representation of left/right acting quaternionic operators, we prove existence and uniqueness for quaternionic initial value problems, discuss the reduction of order for quaternionic homogeneous differential equations and extend to the non-commutative case the method of variation of parameters. We also show that the standard Wronskian cannot uniquely be extended to the quaternionic case. Nevertheless, the absolute value of the complex Wronskian admits a non-commutative extension for quaternionic functions of one real variable. Linear dependence and independence of solutions of homogeneous (right) H-linear differential equations is then related to this new functional. Our discussion is, for simplicity, presented for quaternionic second order differential equations. This involves no loss of generality. Definitions and results can be readily extended to the n-order case.

math-ph↗
arXiv2002

Quaternionic eigenvalue problem

We discuss the (right) eigenvalue equation for $\mathbb{H}$, $\mathbb{C}$ and $\mathbb{R}$ linear quaternionic operators. The possibility to introduce an isomorphism between these operators and real/complex matrices allows to translate the quaternionic problem into an {\em equivalent} real or complex counterpart. Interesting applications are found in solving differential equations within quaternionic formulations of quantum mechanics.

math-ph↗
arXiv2002

Quaternionic differential operators

Motivated by a quaternionic formulation of quantum mechanics, we discuss quaternionic and complex linear differential equations. We touch only a few aspects of the mathematical theory, namely the resolution of the second order differential equations with constant coefficients. We overcome the problems coming out from the loss of the fundamental theorem of the algebra for quaternions and propose a practical method to solve quaternionic and complex linear second order differential equations with constant coefficients. The resolution of the complex linear Schrodinger equation, in presence of quaternionic potentials, represents an interesting application of the mathematical material discussed in this paper.

math-ph↗
arXiv2002

Quaternionic potentials in non-relativistic quantum mechanics

We discuss the Schrodinger equation in presence of quaternionic potentials. The study is performed analytically as long as it proves possible, when not, we resort to numerical calculations. The results obtained could be useful to investigate an underlying quaternionic quantum dynamics in particle physics. Experimental tests and proposals to observe quaternionic quantum effects by neutron interferometry are briefly reviewed.

hep-th↗
arXiv2002

Timelapse

We discuss the existence in an arbitrary frame of a finite time for the transformation of an initial quantum state into another e.g. in a decay. This leads to the introduction of a timelapse $\tildeτ$ in analogy with the lifetime of a particle. An argument based upon the Heisenberg uncertainty principle suggests the value of $\tildeτ=1 / M_0$. Consequences for the exponential decay formula and the modifications that $\tildeτ$ introduces into the Breit-Wigner mass formula are described.

hep-ph↗
arXiv1999

The Dirac-Hestenes Lagrangian

We discuss the variational principle within Quantum Mechanics in terms of the noncommutative even Space Time sub-Algebra, the Clifford $\Ra$-algebra $Cl_{1,3}^+$. A fundamental ingredient, in our multivectorial algebraic formulation, is the adoption of a $\D $-complex geometry, $\D \equiv span_{\RR} \{1,γ_{21} \}$, $γ_{21} \in Cl_{1,3}^+$. We derive the Lagrangian for the Dirac-Hestenes equation and show that such Lagrangian must be mapped on $\D \otimes {\cal F}$, where $\cal F$ denotes an $\Ra$-algebra of functions.

hep-ph↗
arXiv1999

Towards an octonionic world

In order to obtain a consistent formulation of octonionic quantum mechanics (OQM), we introduce left-right barred operators. Such operators enable us to find the translation rules between octonionic numbers and $8\times 8$ real matrices (a translation is also given for $4\times 4$ complex matrices). The use of a complex geometry allows us to overcome the hermiticity problem and define an appropriate momentum operator within OQM. As an application of our results, we develop an octonionic relativistic free wave equation, linear in the derivatives. Even if the wave functions are only one-component we show that four independent solutions, corresponding to those of the Dirac equation, exist.

hep-th↗
arXiv1999

Complex Geometry and Dirac Equation

Complex geometry represents a fundamental ingredient in the formulation of the Dirac equation by the Clifford algebra. The choice of appropriate complex geometries is strictly related to the geometric interpretation of the complex imaginary unit $i=\sqrt{-1}$. We discuss {\em two} possibilities which appear in the multivector algebra approach: the $σ_{123}$ and $σ_{21}$ complex geometries. Our formalism permits to perform a set of rules which allows an immediate translation between the complex standard Dirac theory and its version within geometric algebra. The problem concerning a double geometric interpretation for the complex imaginary unit $i=\sqrt{-1}$ is also discussed.

hep-th↗
arXiv1999

Quaternionic Groups in Physics: A Panoramic Review

Due to the non-commutative nature of quaternions we introduce the concept of left and right action for quaternionic numbers. This gives the opportunity to manipulate appropriately the $H$-field. The standard problems arising in the definitions of transpose, determinant and trace for quaternionic matrices are overcome. We investigate the possibility to formulate a new approach to Quaternionic Group Theory. Our aim is to highlight the possibility of looking at new quaternionic groups by the use of left and right operators as fundamental step toward a clear and complete discussion of Unification Theories in Physics.

hep-th↗
arXiv1997

Breaking the symmetry in bimodal frequency distributions of globally coupled oscillators

The mean-field Kuramoto model for synchronization of phase oscillators with an asymmetric bimodal frequency distribution is analyzed. Breaking the reflection symmetry facilitates oscillator synchronization to rotating wave phases. Numerical simulations support the results based of bifurcation theory and high-frequency calculations. In the latter case, the order parameter is a linear superposition of parameters corresponding to rotating and counterrotating phases.

patt-sol↗