A classical lower bound on the size of a massive neutrino

In this paper, we calculate the size of a massive neutrino in the following approach. We perform our calculation using its mass, spin, and magnetic moment through the neutrino-electron interaction, $via$ the classical magnetic dipole-dipole interaction. Thus, our estimate is obtained by mimicking the low-energy electroweak scattering process $\nu_l$-$l^{\prime}$. This leads to surprisingly accurate result which differs in less than one order of magnitude of more detailed calculations with one-loop corrections based on the neutrino charge radius and the $\nu_l$-$l^{\prime}$ scattering process. The resulting estimates are flavour-blind and gauge independent by construction. We also find that our lower bound is below the reported experimental upper bound on the electron neutrino charged radius. So we obtained a constraining range for the neutrino size.Comment: 5 pages, 1 figur

Fundamental constraints on two-time physics

We show that generalizations of classical and quantum dynamics with two times lead to fundamentally constrained evolution. At the level of classical physics, Newton's second law is extended and exactly integrated in $1+2$ dimensional space, leading to effective single-time evolution for any initial condition. In the domain of quantum mechanics, we follow strictly the hypothesis of probability conservation by extending the Heisenberg picture to unitary evolution with two times. As a result, the observability of two temporal axes is constrained by a generalized uncertainty relation involving level spacings, total duration of the effect and Planck's constant.Comment: 13 pages, 1 figure. This version close to published pape

Second-order Lagrangians admitting a first-order Hamiltonian formalism

Second-order Lagrangian densities admitting a first-order Hamiltonian formalism are studied; namely, i) for each second-order Lagrangian density on an arbitrary fibred manifold $p\colon E\to N$ the Poincar\'e-Cartan form of which is projectable onto $J^1E$, by using a new notion of regularity previously introduced, a first-order Hamiltonian formalism is developed for such a class of variational problems; ii) the existence of first-order equivalent Lagrangians are discussed from a local point of view as well as global; iii) this formalism is then applied to classical Einstein-Hilbert Lagrangian and a generalization of the BF theory. The results suggest that the class of problems studied is a natural variational setting for GR

The stabilizer group of honeycomb lattices and its application to deformed monolayers

Isospectral transformations of exactly solvable models constitute a fruitful method for obtaining new structures with prescribed properties. In this paper we study the stability group of the Dirac algebra in honeycomb lattices representing graphene or boron nitride. New crystalline arrays with conical (Dirac) points are obtained; in particular, a model for dichalcogenide monolayers is proposed and analyzed. In our studies we encounter unitary and non-unitary transformations. We show that the latter give rise to \mbox{\cal P\,}\mbox{\cal T\,}-symmetric Hamiltonians, in compliance with known results in the context of boosted Dirac equations. The results of the unitary part are applied to the description of invariant bandgaps and dispersion relations in materials such as MoS$_2$. A careful construction based on atomic orbitals is proposed and the resulting dispersion relation is compared with previous results obtained through DFT.Comment: 15 pages, 6 figures. This version close to published pape

General circular velocity relation of a test particle in a 3D gravitational potential: application to the rotation curves analysis and total mass determination of UGC 8490 and UGC 9753

In this paper we derive a novel circular velocity relation for a test particle in a 3D gravitational potential applicable to every system of curvilinear coordinates, suitable to be reduced to orthogonal form. As an illustration of the potentiality of the determined circular velocity expression we perform the rotation curves analysis of UGC 8490 and UGC 9753 and we estimate the total and dark matter mass of these two galaxies under the assumption that their respective dark matter halos have spherical, prolate and oblate spheroidal mass distributions. We employ stellar population synthesis models and the total HI density map to obtain the stellar and HI+He+metals rotation curves of both galaxies. The subtraction of the stellar plus gas rotation curves from the observed rotation curves of UGC 8490 and UGC 9753 generates the dark matter circular velocity curves of both galaxies. We fit the dark matter rotation curves of UGC 8490 and UGC 9753 through the newly established circular velocity formula specialised to the spherical, prolate and oblate spheroidal mass distributions, considering the Navarro, Frenk and White, Burkert, Di Cintio, Einasto and Stadel dark matter halos. Our principal findings are the following: globally, cored dark matter profiles Burkert and Einasto prevail over cuspy Navarro, Frenk and White and Di Cintio. Also, spherical/oblate dark matter models fit better the dark matter rotation curves of both galaxies than prolate dark matter halos.Comment: 23 pages, 16 figures, published in MNRAS Main Journa

Diffraction of particles in free fall

The problem of a beam of quantum particles falling through a diffractive screen is studied. The solutions for single and double slits are obtained explicitly when the potential is approximated by a linear function. It is found that the resulting patterns depend on a quasi-time $\tau$ given by a function of the coordinate along the propagation axis in a classical combination $z_0-t^2 F/m$, while the diffraction effects along transverse axes are due solely to $m/\hbar$. The consequences on the precision at which the equivalence principle can be tested are discussed. Realizations with ultra cold neutrons, Bose-Einstein condensates and molecular beams are proposed.Comment: This version accepted for publication, Phys Rev A. 12 pages, 5 figures, double colum

Mass content of UGC 6446 and UGC 7524 through HI rotation curves: deriving the stellar discs from stellar population synthesis models

In this work we study the mass distribution of two irregular galaxies, UGC 6446 and UGC 7524, by means of HI rotation curves derived from high resolution HI velocity fields obtained through the Westerbork Synthesis Radio Telescope data archive. We constrain the stellar and gas content of both galaxies with stellar population synthesis models and by deriving the HI+He+metals rotation curves from the total HI surface density maps, respectively. The discrepancy between the circular velocity maxima of the stellar plus the HI+He+metals rotation curves and the observed HI rotation curves of both galaxies requires the inclusion of a substantial amount of dark matter. We explore the Navarro Frenk and White, Burkert, Di Cintio, Einasto and Stadel dark matter halo models. We obtain acceptable fits to the observed HI rotation curves of UGC 6446 and UGC 7524 with the cored Burkert, Einasto and Stadel dark matter halos. In particular, Einasto and Stadel models prove to be an appropriate alternative to the Burkert dark matter halo. This result should increase the empirical basis that justify the usage of dark matter exponential models to adjust the observed rotation curves of real galaxies.Comment: 18 pages, 16 figures, published in Monthly Notices of the Royal Astronomical Society, Main Journa

Stern-Gerlach splitters for lattice quasispin

We design a Stern-Gerlach apparatus that separates quasispin components on the lattice, without the use of external fields. The effect is engineered using intrinsic parameters, such as hopping amplitudes and on-site potentials. A theoretical description of the apparatus relying on a generalized Foldy-Wouthuysen transformation beyond Dirac points is given. Our results are verified numerically by means of wavepacket evolution, including an analysis of Zitterbewegung on the lattice. The necessary tools for microwave realizations, such as complex hopping amplitudes and chiral effects, are simulated.Comment: 10 pages, 11 figures, added closest version to the published one; corrected typos, formulas and figures rearranged, added appendi

Fabry-Perot Kinematics of HH 202, 203-204 in the Orion Nebula: Are they part of a Big Bipolar Outflow?

We present a kinematic study of the Herbig-Haro objects HH 202, 203 and 204 using Halpha and [NII] Fabry-Perot velocity maps. For HH 202 we find new features that could belong to this HH object or that perhaps are associated with an outflow different from HH 202. Because of its high velocity (up to 100 km/seg) this outflow probably can be a HH flow not catalogued previously. Large internal motions are found in the fainter regions of HH 203-204, as well as evidence of transverse density gradients. We show that the apex of HH 204 is the zone of maximum velocity in agreement with bow shock models. From our studies, we find kinematic evidence that suggests that HH 203-204 and HH 202 are part of a single and large (approx 0.55 pc) HH flow.Comment: 11 pages, 4 figures (in one JPG file). To appear in "Emission Lines From Jet Flows", Rev. Mex. Astron. and Astrofis. Conf. Se

Disk Mass-to-Light ratio distribution from stellar population synthesis: Application to rotation curve decomposition of NGC 5278 (KPG 390A)

In this work we extend the study on the mass distribution of the spiral galaxy NGC 5278, performing 1D and 2D bulge-disk decomposition to determine which components constitute the baryonic mass in this galaxy. Our analysis does not detect any bulge, instead we find a bright source, probably related with the central AGN, and an exponential disk. We fix the stellar disk contribution to the rotation curve (RC) with broad band photometric observations and population synthesis models, to obtain 2D mass distribution of the stellar disk. In the particular case of NGC 5278, we find that the typical assumption of considering the mass-to-luminosity ratio (M/L) of the disk as constant along the galactocentric radius is not valid. We also extract a baryonic RC from the mass profile, to determine the inability of this baryonic RC and also of the baryonic RC with more and less 30% disk mass (in order to consider the disk mass errors) to fit the entire RC. We perform the RC decomposition of NGC 5278 considering the baryonic RC and four types of dark matter halos: Hernquist; Burkert; Einasto and Navarro, Frenk & White. Our results show that Hernquist halo models better our observed RC in the case of determined disk mass ($M_d=5.6\times 10^{10}$ solar masses) and also with 30% less disk mass. In the case of 30% more disk mass the cored Einasto (n < 4) halo is the best fitting model.Comment: 24 pages, 15 figures. Grammar checked. Accepted by Ap