Privileged Direction Research Articles

Constants of motion characterizing continuous symmetry-broken phases.

We present a theory characterizing the phases emerging as a consequence of continuous symmetry-breaking in quantum and classical systems. In symmetry-breaking phases, dynamics is restricted due to the existence of a set of conserved charges derived from the order parameter of the phase transition. Their expectation values are determined by the privileged direction appearing in the ordered phase as a consequence of symmetry breaking, and thus they can be used to determine whether this direction is well defined or has quantum fluctuations. Our theory is numerically exemplified via the two-dimensional limit of the vibron model, a fully connected system invariant under a rotation operator which generates the continuous symmetry-breaking.

Lorentz violation in γ-pair production (e + e − → γ γ)

In this paper, we investigate the production process of a photon pair in a regime of quantum electrodynamics, considering the presence of a constant four-vector that defines a privileged direction in spacetime, resulting in Lorentz symmetry violation. We explore Lorentz violation in the context of vectorial nonminimal coupling, where we analyze the modifications introduced by this coupling in the scattering amplitude at the vertex. Moreover, we delve into Lorentz violation with axial-like nonminimal coupling. Both analyses are conducted by examining the constant four-vector of both time-like and space-like types.

Barkhausen noise hysteresis cycle: Theoretical and experimental understanding

Magnetic Barkhausen Noise (MBN) reflects magnetic domains’ motions during a ferromagnetic part’s magnetization process. For industrial specimens, the raw MBN signal is stochastic and not reproducible, leading to complex analyses. This issue is solved using time-average variables like the Magnetic Barkhausen Noise energy (MBNenergy).Plotting MBNenergy as a function of the magnetic excitation gives rise to a hysteresis cycle. Recent studies have highlighted some exciting properties from this cycle, such as a way to observe the magnetic loss contribution associated with the domain wall motions. Still, questions remain, including in the basic description of MBNenergy.This paper describes a theoretical development to understand MBNenergy further. We demonstrate that in standard characterization conditions, the magnetization variations associated with the domain wall motions are proportional to the square of the envelope of the MBN signal instead of its absolute value.Then, this theoretical conclusion is confirmed experimentally. Finally, the absence of privileged orientation and direction in the MBN effect is verified in the case of unidirectional magnetization.

Congruity of the Crab Pulsar’s γ-ray spectrum with the spectral distribution of tightly focused caustics

The spectrum derived here for the most tightly focused component of the radiation generated by the super-luminally moving current sheet in the magnetosphere of a non-aligned neutron star has a distribution function that fits the entire γ-ray spectrum of the Crab Pulsar on its own. This is the first time that the undivided breadth of this spectrum, from 102 to 106 MeV, is not only described by a single distribution function but is also explained by means of a single emission mechanism. To illustrate that the derived function describes the spectral distribution of the high-energy emission from any non-aligned neutron star, we analyse, in addition, the spectra of two other γ-ray pulsars for which sufficiently large datasets are available: PSR J0101−6422 and PSR J1709−4429. From the connection between the parameters of the fitted spectra and the physical characteristics of their sources, we moreover infer certain attributes of the magnetospheres of the analysed pulsars: the angle between the magnetic and spin axes of their central neutron stars, the scale factor of the electric current density that is associated with their current sheet, and the privileged latitudinal direction (relative to the spin axis) in which they are observed.

Wittgensteins Kritik am additiven Verständnis des sprachlichen Zeichens

Abstract This paper argues that Wittgenstein, both early and late, rejects the idea that the logically simpler and more fundamental case is that of “the mere sign” and that what a meaningful symbol is can be explained through the elaboration of an appropriately supplemented conception of the sign: the sign plus something (say, an interpretation or an assignment of meaning). Rather the sign, in the logically fundamental case of its mode of occurrence, is an internal aspect of the symbol. The Tractatus puts this point as follows: “The sign is that in the symbol which is perceptible by the senses.” Conversely, this means that it is essential to a symbol – to what a symbol is – that it have an essentially perceptible aspect. For Wittgenstein there is no privileged direction of explanatory priority between symbol and sign here: without signs there are no symbols (hence without language there is no thought) and without some sort of relation to symbols there are no signs (hence the philosopher’s concept of the supposedly “merely linguistic” presupposes an internal relation to symbols).

Supersolid striped droplets in a Raman spin-orbit-coupled system

We analyze the role played by quantum fluctuations on a Raman Spin-Orbit Coupled system in the stripe phase. We show that beyond mean-field effects stabilize the collapse predicted by mean-field theory and induce the emergence of two phases: a gas and a liquid, which also show spatial periodicity along a privileged direction. We show that the energetically favored phase is determined by the Raman coupling and the spin-dependent scattering lengths. We obtain the ground-state solution of the finite system by solving the extended Gross-Pitaevskii equation and find self-bound, droplet-like solutions that feature internal structure through a striped pattern. We estimate the critical number for binding associated to these droplets and show that their value is experimentally accessible. We report an approximate energy functional in order to ease the evaluation of the Lee-Huang-Yang correction in practical terms.

Windcatchers and their applications in contemporary architecture

Natural ventilation and cooling have played an essential role in providing comfort conditions. Windcatchers are passive cooling systems and one of the most familiar elements in Iranian architecture. They can significantly influence on reduce cooling loads and supply the necessary ventilation rate of buildings. This paper aims at providing an in-depth review of the recent developments and applications of windcatchers in modern architecture. The efficiency of windcatcher is also discussed according to the windcatcher's relevant parameters, i.e., height, configuration, and cross-section. This comprehensive review reveals that these factors have significant impacts on the performance of windcatchers. It is also shown that a one-sided windcatcher is a better choice in regions with privileged wind direction. However, other types of it are better in regions with variable wind directions. Finally, windcatchers' potential for applying in the contemporary architecture and urban planning shown in the using windcatcher in contemporary buildings, windcatchers in the urban context, new designs, and new technologies of windcatchers sections.

Properties of DNA-CTMA monolayers obtained by Langmuir-Blodgett technique

The complex consisting of DNA and cetyltrimethylammonium chloride (DNA-CTMA) is extensively exploited in organic electronics in form of thin films with submicron or nanometer thickness. In this work, using the Langmuir-Blodgett technique, the surface films were prepared from complexes based on different types of chromosomal and plasmid DNA. The research focused on changes in their continuity after they were transferred onto a solid substrate. It was found that only the monolayer of plasmid DNA-CTMA complex remained continuous after being transferred. The other complexes underwent a spontaneous self-assembling and created elongated linear patterns. AFM images of these patterns were analysed quantitatively with Fast Fourier Transform. It was confirmed that self-assembling occurred along one privileged direction.

Geometrically driven liquid wicking: numerical study and experimental validation

Liquid film or drop wicking on solid surface without any external energy input is highly desirable in specific industrial processes. This paper proposes a numerical study of the dynamics of liquid wicking on geometrically structured flat surface. We consider structures deduced from flat surface by super-imposing a series of identical parallel channels, the ensemble being made of the same material. Channels exhibit arrow-shaped patterns. We analyse drop wicking on such a structure using numerical simulation and experiment. Both approaches reveal non symmetric wicking clearly exhibiting a privileged direction. The simulation captures the evolution of the liquid/air interface at smaller time scales and reveals wicking with rapid pulses suggested by the experiment.

Quantum aspects of the Lorentz symmetry violation on an electron in a nonuniform electric field

By focusing on the interface between quantum field theory and nonrelativistic quantum mechanics, based on a theory that goes beyond the Standard Model, we consider the hypothesis of having a privileged direction in the space-time. This hypothesis is made by considering a background of the Lorentz symmetry violation determined by a fixed space-like vector field. Then, we analyse quantum effects of this background on the interaction of a nonrelativistic electron with a nonuniform electric field produced by a uniform electric charge distribution.

Wittgenstein’s Critique of the Additive Conception of Language

This paper argues that Wittgenstein, both early and late, rejects the idea that the logically simpler and more fundamental case is that of "the mere sign" and that what a meaningful symbol is can be explained through the elaboration of an appropriately supplemented conception of the sign: the sign plus something (say, an interpretation or an assignment of meaning). Rather the sign, in the logically fundamental case of its mode of occurrence, is an internal aspect of the symbol. The Tractatus puts this point as follows: “The sign is that in the symbol which is perceptible by the senses.” Conversely, this means that it is essential to a symbol – to what a symbol is – that it have an essentially perceptible aspect. For Wittgenstein there is no privileged direction of explanatory priority between symbol and sign here: without signs there are no symbols (hence without language there is no thought) and without some sort of relation to symbols there are no signs (hence the philosopher’s concept of the supposedly "merely linguistic" presupposes an internal relation to symbols).

Optical Properties of Titanium in the Regime of the Limited Light Penetration

In this study, the titanium layers from 12 to 1470 nm thick were fabricated by using the method involving dynamically changed working gas pressure (gas injection magnetron sputtering). The influence of the deposition time on the optical and electrical properties of Ti films, as well as on their microstructure, are considered. The samples are investigated by means of spectroscopic ellipsometry, atomic force microscopy, X-ray diffraction, and confocal optical microscopy. Additionally, for the Ti layers, the sheet resistance was determined. The produced coatings exhibit privileged direction of growth (002). The obtained results show a gradual increase in the mean relaxation time of free-carriers with the increase in the thickness of titanium film. However, the plasma energy exhibits maximum for the coating with the thickness of 93 nm. For such thickness, the lowest value of optical resistivity (about 200 cm) was observed. It was found that the dc- and optical resistivity exhibit similar values for titanium films with thickness up to 93 nm. For thicker Ti layers, significant differences in resistivities (dc- and optical) were noticed. The behavior of the Drude parameter (the plasma energy), calculated optical resistivity, and discrepancies between values of optical and dc-resistivities for thicker Ti coatings can be explained as a result of the limited light penetration.

Photon mass in very special relativity

In Very Special Relativity (VSR) a gauge invariant photon mass is allowed. We explore some consequences of keeping this parameter not zero. VSR-Maxwell equations are presented. In addition, we show modifications to the Feynman rules keeping the photon mass and we apply it in the computation of the electron self energy, whose result is free from infrared divergences. A computation of the Coulomb scattering is developed and a small signal of the privileged direction predicted in the theory is present at tree level. Radiative corrections are computed and the photon mass cancels due to soft photon emission as in the standard case.

Assessing the extent of citrus trees root apparatus under deficit irrigation via multi-method geo-electrical imaging

Tree rooting strategies are driven by external and internal factors such as climate conditions (rain frequency, wind direction), soil structure and crop type. In order to ensure water efficiency for irrigated crops, it is essential to know how each crop adapts its rooting strategy. We couple Mise-a-la-masse (MALM) with Electrical Resistivity Tomography (ERT) for investigating orange tree roots undergoing different irrigation strategies (Partial Root-zone Drying – or PRD - versus Full Irrigation). This is a totally novel approach giving an overall picture of roots structure and functioning in the subsoil. Our results show clear differences of rooting extent between different irrigation strategies, and identify privileged direction of root development due to distinct RWU patterns. These results are corroborated also by seasonal monitoring of evapotranspiration (ET) and soil water content (SWC), which exhibit very large differences in the soil water distribution in space and time for the trees undergoing different irrigation schedules.

Study of the geometrical structure of copper surface after abrasive waterjet cutting

The article concerns the assessment of the intersection structure of copper samples after abrasive waterjet (AWJ) cutting. The surface quality of the processed material was tested on a macroscopic and microscopic scale. The assessments of surface quality was carried out in two characteristic areas of the cutting surface. The macroscopic studies concerned the evaluation of post-treatment cutting traces, with particular emphasis on the trajectory of the stream. Microscopic study of the geometric structure of the surface included the assessment of the conditions of impact of individual abrasive grains with the surface treated by using AWJ cutting. Characteristic orientations of machining traces were observed on the treated surface. The surface of the cutting zone located at the inlet of the stream to material is characterized a better cutting quality with visible of a privileged direction of traces of the impact of abrasive grains on the machined surfaces. As a result of the decrease of the kinetic energy of the cutting jet along with material penetration the surface at the outlet of the stream from the cut material, a surface characterized by the occurrence of multi-directional traces of abrasive grains. In this area are visible traces of decohesion of the workpiece in the form of microgrooves. In the studied areas, the effect of embedding fragments of crushed grains on the surface of the processed material was observed.

On the effects of the Lorentz symmetry violation yielded by a tensor field on the interaction of a scalar particle and a Coulomb-type field

We analyse the interface between a theory that goes beyond the Standard Model and quantum mechanics. Based on a line of research that deals with the violation of the Lorentz symmetry, where it is assumed that at least one privileged direction in the spacetime, studies have been made in search of a hint of a fundamental theory that goes beyond the energy scale of the Standard Model. This fundamental theory describes a spontaneous breaking of the Lorentz symmetry by a tensor background, which can be considered to be a perturbation. Then, we analyse the interaction of a scalar particle with a Coulomb-type potential in the presence of a background of the violation of the Lorentz symmetry established by a tensor field.

Abelian 1-Form Gauge Theory in Very Special Relativity

We study an Abelian 1-form gauge theory in the context of very special relativity. The very special relativity regards subgroup of Lorentz group as fundamental symmetry of the nature than the full Lorentz group. The rotational symmetry of the Lorentz symmetry breaks down by chosing a privileged direction in spacetime. We discuss the BRST invariant and anti-BRST invariant superspace formulations for such BV actions. The VSR modified BRST invariant BV action corresponding to the Abelian 1-form gauge theory can be written manifestly covariant manner in a superspace with one Grassmann coordinate. Moreover, we can write down the the VSR modified extended BRST and extended anti-BRST invariant BV actions in a superspace with two Grassmann coordinates. The results thus obtained is in complete agreement with the Lorentz invariant theory.

A novel treatment of Greenwood–Johnson’s mechanism of transformation plasticity - Case of spherical growth of nuclei of daughter-phase

This paper proposes an innovative treatment of Greenwood and Johnson (1965)’s mechanism of transformation plasticity of metals and alloys, based on the disregard of elasticity and the powerful kinematic method of limit-analysis. In the new approach the spherical representative unit cell considered in the homogenization process includes only the mother-phase surrounding a growing nucleus of daughter-phase, but the external loading arising from the macroscopic stress applied is supplemented with an internal one arising from the volumetric transformation strain of the enclosed nucleus. The treatment brings considerable improvement to the classical one of Leblond et al. (1989), not only by eliminating the need for ad hoc hypotheses of limited validity, but more importantly by extending its results to more general situations involving large external stresses, comparable in magnitude to the yield stress of the weaker, mother-phase. The theoretical results are compared to other theories, experiments, and finite element micromechanical simulations considering a representative volume of shape identical to that in the theory. In addition, the methodology presented paves the way to incorporation, in a future work, of the effect of anisotropies of morphologic type (tied for instance to growth of nuclei of daughter-phase elongated in a certain privileged direction) upon transformation plasticity; this will be done through consideration of representative unit cells of more complex shape.

Causal Asymmetry in a Quantum World

Causal asymmetry is one of the great surprises in predictive modelling: the memory required to predict the future differs from the memory required to retrodict the past. There is a privileged temporal direction for modelling a stochastic process where memory costs are minimal. Models operating in the other direction incur an unavoidable memory overhead. Here we show that this overhead can vanish when quantum models are allowed. Quantum models forced to run in the less natural temporal direction not only surpass their optimal classical counterparts, but also any classical model running in reverse time. This holds even when the memory overhead is unbounded, resulting in quantum models with unbounded memory advantage.

Self-calibration of omnidirectional multi-cameras including synchronization and rolling shutter

360° and spherical cameras become popular and are convenient for applications like immersive videos. They are often built by fixing together several fisheye cameras pointing in different directions. However their complete self-calibration is not easy since the consumer fisheyes are rolling shutter cameras which can be unsynchronized. Our approach does not require a calibration pattern. First the multi-camera model is initialized thanks to assumptions that are suitable to an omnidirectional camera without a privileged direction: the cameras have the same setting and are roughly equiangular. Second a frame-accurate synchronization is estimated from the instantaneous angular velocities of each camera provided by monocular structure-from-motion. Third both inter-camera poses and intrinsic parameters are refined using multi-camera structure-from-motion and bundle adjustment. Last we introduce a bundle adjustment that estimates not only the usual parameters but also a sub-frame-accurate synchronization and the rolling shutter. We experiment using videos taken by consumer cameras mounted on a helmet and moving along trajectories of several hundreds of meters or kilometers, and compare our results to ground truth.