Catálogo de publicaciones - revistas

<jats:p>Dark matter remains one of the most significant scientific mysteries of our time. This Resource Letter provides an overview of the astrophysical evidence for dark matter and describes the broad set of theoretical dark matter candidates that have been proposed. Results from dark matter searches are discussed, with a focus on direct detection experiments.</jats:p>

<jats:p>A general solution to the problem of relativistic acceleration of point objects in the noninertial frame of any of the objects is given in one spatial dimension. The objects are initially at rest in a common inertial frame and accelerate until they are at rest in a second inertial frame. The starting time and position of each object, the acceleration rate of each object, and the number of objects are arbitrary. The solution gives the position and velocity of each object in the noninertial frame of the host object, and the proper time of each, as functions of the proper time of the host. The method is based on system states for a pair of objects, and it is found that there are nine series of states which cover all cases, including those in which objects are separated from the host by its Rindler horizon. The familiar problems of acceleration of an elastic rod and a (Born) rigid rod are treated, and a number of examples are given of spaceflight sequences for multiple craft in tandem.</jats:p>

<jats:p>The factorization method of Schrödinger shows us how to determine the energy eigenstates without needing to determine the wavefunctions in position or momentum space. A strategy to convert the energy eigenstates to wavefunctions is well known for the one-dimensional simple harmonic oscillator by employing the Rodrigues formula for the Hermite polynomials in position or momentum space. In this work, we illustrate how to generalize this approach in a representation-independent fashion to find the wavefunctions of other problems in quantum mechanics that can be solved by the factorization method. We examine three problems in detail: (i) the one-dimensional simple harmonic oscillator; (ii) the three-dimensional isotropic harmonic oscillator; and (iii) the three-dimensional Coulomb problem. This approach can be used in either undergraduate or graduate classes in quantum mechanics.</jats:p>

<jats:p>Statistical physics courses typically employ abstract language that describes objects too small to be seen, making the topic challenging for students to understand. In this work, we introduce a simple experiment that allows conceptualizing some of the underlying ideas of stochastic processes through direct experimentation. Students analyze stochastic trajectories of beads in a bouncing bed of smaller beads subjected to an external periodic drive. The analysis of the trajectories involves the application of a vast toolkit of statistical estimators that are useful in many fields of physics.</jats:p>

<jats:p>The trapping potential induced by the interaction of a highly focused laser light with a spherical dielectric particle can be accurately approximated by a parabolic potential. In this work, we revisit experimental and numerical methodologies used to characterize the Brownian motion of a colloidal particle under the influence of a simple harmonic potential produced by optical tweezers. A classic Brownian dynamics simulation is used to model the experimental results, focusing on statistical properties that can be measured by direct visualization of the system using videomicroscopy. This work represents a useful insight into the underlying physics behind the optical tweezers technique, also giving guidelines regarding programming protocols and experimental analysis methodologies, that may be of help for students working with such techniques, as well as for professors teaching undergraduate advanced optics courses.</jats:p>

<jats:p>The distribution of the time elapsed before a random variable reaches a threshold value for the first time, called the first passage time (FPT) distribution, is a fundamental characteristic of stochastic processes. Here, by solving the standard macroscopic diffusion equation, we derive analytical expressions for the FPT distribution of a diffusing particle hitting a spherical object in two dimensions (2D) and three dimensions (3D) in the course of unrestricted diffusion in open space. In addition, we calculate, analytically, the angular dependence of the FPT, known as the hit distribution. The analytical results are also compared to simulations of the motions of a random walker on a discrete lattice. This topic could be of wide pedagogical interest because the FPT is important not only in physics but also in chemistry, biology, medicine, agriculture, engineering, and finance. Additionally, the central equations often appear in physics and engineering with only trivial variations, making the solution techniques widely applicable.</jats:p>

<jats:p>The interference of single photons going through a double slit is a compelling demonstration of the wave and particle nature of light in the same experiment. Single photons produced by spontaneous parametric down-conversion can be used for this purpose. However, it is particularly challenging to implement this due to coherency and resolution challenges. In this article, we present a table-top laboratory arrangement suitable for the undergraduate instruction laboratory that overcomes these challenges. The apparatus scans a single detector to produce a plot showing the interference patterns of single photons. We include experimental data obtained using this setup, demonstrating double-slit and single-slit interference as well as quantum erasing through the use of sheet polarizers.</jats:p>