Galilei Group Research Articles

Galileon inflation evades the no-go for PBH formation in the single-field framework

We consider Galileon inflation in the Effective Field Theory (EFT) framework and examine the possibility for PBH formation during slow roll (SR) to ultra slow roll (USR) transitions. We show that loop corrections to the power spectrum, in this case, do not impose additional constraints on the masses of PBHs produced. We indicate that the remarkable non-renormalization property of Galileans due to generalized shift symmetry dubbed as Galilean symmetry is responsible for protecting PBH formation from quantum loop corrections.

The Asymptotic Structure of the Centred Hyperbolic 2-Monopole Moduli Space

We construct an asymptotic metric on the moduli space of two centred hyperbolic monopoles by working in the point particle approximation, that is treating well-separated monopoles as point particles with an electric, magnetic and scalar charge and re-interpreting the dynamics of the 2-particle system as geodesic motion with respect to some metric. The corresponding analysis in the Euclidean case famously yields the negative mass Taub-NUT metric, which asymptotically approximates the L<sup>2</sup> metric on the moduli space of two Euclidean monopoles, the Atiyah-Hitchin metric. An important difference with the Euclidean case is that, due to the absence of Galilean symmetry, in the hyperbolic case it is not possible to factor out the centre of mass motion. Nevertheless we show that we can consistently restrict to a 3-dimensional configuration space by considering antipodal configurations. In complete parallel with the Euclidean case, the metric that we obtain is then the hyperbolic analogue of negative mass Taub-NUT. We also show how the metric obtained is related to the asymptotic form of a hyperbolic analogue of the Atiyah-Hitchin metric constructed by Hitchin.

Action for N D0-branes invariant under gauged Galilean transformations

In this short note we formulate an action for N D0-branes that is manifestly invariant under gauged Galilean transformations. We also find its canonical form and determine first class constraints that are generators of gauge transformations.

Remarks on higher Schwarzians

The Schwarzian derivative has recently received renewed attention in connection with the study of the Sachdev–Ye–Kitaev model. In mathematics literature, various higher order generalizations of the Schwarzian derivative are known due to Aharonov, Bertilsson, and Schippers. Physical applications of the higher Schwarzian derivatives have not yet been discussed in any detail. In this work, we link Bertilsson's variant to the ℓ–conformal Galilei group, as well as discuss some of its interesting peculiarities. These include a recurrence relation, which allows one to construct the higher Schwarzians iteratively, a composition law, and symmetry transformations.

Covariance properties under natural image transformations for the generalised Gaussian derivative model for visual receptive fields.

The property of covariance, also referred to as equivariance, means that an image operator is well-behaved under image transformations, in the sense that the result of applying the image operator to a transformed input image gives essentially a similar result as applying the same image transformation to the output of applying the image operator to the original image. This paper presents a theory of geometric covariance properties in vision, developed for a generalised Gaussian derivative model of receptive fields in the primary visual cortex and the lateral geniculate nucleus, which, in turn, enable geometric invariance properties at higher levels in the visual hierarchy. It is shown how the studied generalised Gaussian derivative model for visual receptive fields obeys true covariance properties under spatial scaling transformations, spatial affine transformations, Galilean transformations and temporal scaling transformations. These covariance properties imply that a vision system, based on image and video measurements in terms of the receptive fields according to the generalised Gaussian derivative model, can, to first order of approximation, handle the image and video deformations between multiple views of objects delimited by smooth surfaces, as well as between multiple views of spatio-temporal events, under varying relative motions between the objects and events in the world and the observer. We conclude by describing implications of the presented theory for biological vision, regarding connections between the variabilities of the shapes of biological visual receptive fields and the variabilities of spatial and spatio-temporal image structures under natural image transformations. Specifically, we formulate experimentally testable biological hypotheses as well as needs for measuring population statistics of receptive field characteristics, originating from predictions from the presented theory, concerning the extent to which the shapes of the biological receptive fields in the primary visual cortex span the variabilities of spatial and spatio-temporal image structures induced by natural image transformations, based on geometric covariance properties.

Galilean fermions: Classical and quantum aspects

We study the classical and quantum "properties" of Galilean fermions in 3+1 dimensions. We have taken the case of massless Galilean fermions minimally coupled to the scalar field. At the classical level, the Lagrangian is obtained by null reducing the relativistic theory in one higher dimension. The resulting theory is found to be invariant under infinite Galilean conformal symmetries. Using Noether's procedure, we construct the corresponding infinite conserved charges. Path integral techniques are then employed to probe the quantum "properties" of the theory. The theory is found to be renormalizable. A novel feature of the theory is the emergence of mass scale at the first order of quantum correction. The conformal symmetry of the theory breaks at the quantum level. We confirm this by constructing the beta function of the theory.

Quantum origin of (Newtonian) mass and Galilean relativity symmetry

Quantum origin of (Newtonian) mass and Galilean relativity symmetry

The shadow formalism of Galilean CFT2

In this work, we develop the shadow formalism for two-dimensional Galilean conformal field theory (GCFT2). We define the principal series representation of Galilean conformal symmetry group and find its relation with the Wigner classification, then we determine the shadow transform of local operators. Using this formalism we derive the OPE blocks, Clebsch-Gordan kernels, conformal blocks and conformal partial waves. A new feature is that the conformal block admits additional branch points, which would destroy the convergence of OPE for certain parameters. We establish another inversion formula different from the previous one, but get the same result when decomposing the four-point functions in the mean field theory (MFT). We also construct a continuous series of bilocal actions of MFT, and an exceptional series of local actions, one of which is the BMS free scalar model. We notice that there is an outer automorphism of the Galilean conformal symmetry, and the GCFT2 can be regarded as null defect in higher dimensional CFTs.

Integrating effects of Carreau–Yasuda slime on bacterial hydrodynamics

This work deals with gliding motion of bacteria over a non-Newtonian slime layer attached to a solid substrate. The surface of a glider is approximated with a simple wavy two-dimensional sheet while the sticky slime is modeled as Carreau–Yasuda fluid. The classical Navier–Stokes equations are transformed by using Galilean transformation and dimensionless variables. Flow beneath the organism is creeping and the lubrication assumption is also valid in this scenario, hence the equation is reduced to fourth-order BVP in terms of stream function. The basic purpose is to compute the gliding speed and flow rate of the slime which are present in the boundary conditions. MATLAB built-in bvp5c solver is utilized to calculate the numerical solution of the stream function. Further, unknowns (flow rate and cell speed) are refined by using modified Newton–Raphson method (MNRT). Further, these pairs are employed in the formula of energy expended. Velocity and stream function is also plotted for these computed pairs. This study is motivated by scientific interest and the desire to understand the dynamics of gliding bacteria. The findings of this study are thought to be beneficial in the development of artificial crawlers.

Evaluation of the performance of fractional evolution equations based on fractional operators and sensitivity assessment

In this article, the nonlinear fractional Kudryashov’s equation and the space–time fractional nonlinear Tzitzeica–Dodd–Bullough (TDB) equation are solved using the new auxiliary equation method, which yields innovative analytical solutions using β and M-Truncated fractional derivatives. The fractional wave and Painlevé transformations are implemented to transform the space and time fractional nonlinear equations into a nonlinear ordinary differential equation. The model solutions are compared by utilizing the two fractional derivatives. Hyperbolic, trigonometric, rational, exponential, and other sorts of soliton solutions are discovered, and these forms of the outcomes illustrate the superiority of the method’s uniqueness. The solutions provided in this piece are sophisticated and comprehensive, and the results of the literature review are one instance of the findings. The key advantage of this approach over remedies is that it possesses higher options with flexible constraints. By plotting 3D as well as 2D graphs of the acquired results and analyzing the effect of the fractional parameter ρ on the wave profiles of the phenomenon, it has been determined that the fractional parameter significantly affects the wave profiles. The findings are carried out in such a way as to showcase the applicability and expertise of fractional derivatives and the proposed approach to evaluate several nonlinear fractional partial differential equations. Finally, the comprehensive sensitivity analysis of the proposed models is done by first transforming it into the format of a planer dynamical system using the Galilean transformation.

Entropy Generation in Peristaltic Transport of Hybrid Nanofluids with Thermal Conductivity Variations and Electromagnetic Effects.

Entropy generation in peristaltic transport of hybrid nanofluid possessing temperature-dependent thermal conductivity through a two-dimensional vertical channel is studied in this paper. The hybrid nanofluid consists of multi-walled carbon nanotubes mixed with zinc oxide suspended in engine oil. Flow is affected by a uniform external magnetic field, hence generating Lorentz force, Hall and heating effects. Given the vertical orientation of the channel, the analysis accounts for mixed convection. To study heat transfer in the current flow configuration, the model considers phenomena such as viscous dissipation, heat generation or absorption, and thermal radiation. The mathematical modeling process employs the lubrication approach and Galilean transformation for enhanced accuracy. The slip condition for the velocity and convective conditions for the temperature are considered at the boundaries. The study analyzes entropy generation using the Homotopy Analysis Method (HAM) and includes convergence curves for HAM solutions. Results are presented using graphs and bar charts. The analysis shows that higher Brinkman and thermal radiation parameters result in higher temperatures, while higher thermal conductivity parameters lead to reduced entropy generation and temperature profile. Additionally, higher Hall parameter values decrease entropy generation, while an increased Hartman number improves entropy generation.

Particle dynamics on torsional galilean spacetimes

We study free particle motion on homogeneous kinematical spacetimes of galilean type. The three well-known cases of Galilei and (A)dS–Galilei spacetimes are included in our analysis, but our focus will be on the previously unexplored torsional galilean spacetimes. We show how in well-chosen coordinates free particle motion becomes equivalent to the dynamics of a damped harmonic oscillator, with the damping set by the torsion. The realization of the kinematical symmetry algebra in terms of conserved charges is subtle and comes with some interesting surprises, such as a homothetic version of hamiltonian vector fields and a corresponding generalization of the Poisson bracket. We show that the Bargmann extension is universal to all galilean kinematical symmetries, but also that it is no longer central for nonzero torsion. We also present a geometric interpretation of this fact through the Eisenhart lift of the dynamics.

The Failure of Both Einstein’s Space-time Theory and His Equivalence Principle and Their Resolution by the Uniform Scaling Method

The Lorentz transformation (LT) makes three predictions which are not consistent with one another: Lorentz-FitzGerald length contraction (FLC), time dilation (TD) and light-speed equality for observers in relative motion to one another. The LT also stands in violation of the Law of Causality because it fails to recognize that inertial clocks can never change their rate spontaneously. Einstein’s light-speed postulate (LSP) is shown to be unviable by considering a case in which a light source passes by a stationary observer at the same time that it emits a light pulse in the same direction. It is found that, in contradiction to the LSP, that the classical velocity (Galilean) transformation (GVT) is applicable when two observers in relative motion deduce the speed of a light wave. The Newton-Voigt transformation (NVT) is consistent with the Law of Causality because it assumes space and time do not mix. The NVT is nonetheless consistent with the relativistic velocity transformation (RVT) and also with Einstein’s mass-energy equivalence relation E=mc2. The ratio Q of clock rates for two inertial rest frames S and S’ is required input for the NVT. Experimental data obey the Universal Time-dilation Law (UTDL) which states that the measured time Δt obtained by a inertial clock for a given event is inversely proportional to γ(v)= (1-v2c-2)-0.5v, where v is the speed of the clock relative to a specific rest frame referred to as the objective rest frame ORS. The value of Q when the clock of the observer in at rest in S while that of another observer is at rest in the object’s rest frame S’ is obtained from the UTDL as the ratio γ(v’)/γ(v). The Uniform Scaling method considers Q to be a conversion factor between the units of time in the two rest frames. It is found that the conversion factors for all other physical properties are integral multiples of Q. Kinetic scaling of the properties insures that the laws of physics are the same in each inertial frame, as required .........

Nonrelativistic spin-3 symmetries in 2+1 dimensions from expanded and extended Nappi-Witten algebras

We show that infinite families of Galilean spin-3 symmetries in $2+1$ dimensions, which include higher-spin extensions of the Bargmann, Newton-Hooke, nonrelativistic Maxwell, and nonrelativistic AdS-Lorentz algebras, can be obtained as Lie algebra expansions of two different spin-3 extensions of the Nappi-Witten symmetry. These higher-spin Nappi-Witten algebras, in turn, are obtained by means of In\"on\"u-Wigner contractions applied to suitable direct product extensions of $\mathfrak{s}\mathfrak{l}(3,\mathbb{R})$. Conversely, we show that the same result can be obtained by considering contractions of expanded $\mathfrak{s}\mathfrak{l}(3,\mathbb{R})$ algebras. The method can be used to define nonrelativistic higher-spin Chern-Simon gravity theories in $2+1$ dimensions in a systematic way.

Soliton structures and dynamical behaviors for the integrable system of Drinfel’d–Sokolov–Wilson equations in dispersive media

This study is used to investigate the exact explicit solutions and dynamical behaviors of the (1+1)-dimensional integrable system of Drinfel’d–Sokolov–Wilson equations in dispersive media. Firstly, the unified method is implemented to find explicit solutions in polynomial and rational forms. These solutions include rational, dark and bright soliton structures. After that, the planar dynamical system of the considered model is obtained using the Galilean transformation. The phase portraits of the bifurcations are drawn from the planar dynamical system for different physical parametric values using the fourth-order Runge–Kutta method. Further, an external force is imposed on the dynamical system to observe the phase portraits of chaotic trajectories. These tracks are outlined for different values of the strength and frequency of the external force acting on the dynamical system. The outcomes show that a given model has chaotic behvior as its solution becomes disordered by taking small variation in the strength and frequency of the external force. The results are new and can be helpful in investigating the dynamical behaviors of the other nonlinear physical models arising in optics, bio-mathematics and so many other fields of science.

Space and time transformations with a minimal length

Phenomenological studies of quantum gravity have proposed a modification of the commutator between position and momentum in quantum mechanics to introduce a minimal uncertainty in position in quantum mechanics. In the present work, we show the influence of space and time transformations in shaping quantities such as momentum, energy, and their relations with the generators of transformations. Thus, such an influence determines, among other aspects, the time evolution of a quantum system. In the exemplary case of Galilean transformations, the Schrödinger equation is identical to the ordinary case.

Whitham modulation theory for the defocusing nonlinear Schrödinger equation in two and three spatial dimensions

The Whitham modulation equations for the defocusing nonlinear Schrödinger (NLS) equation in two, three and higher spatial dimensions are derived using a two-phase ansatz for the periodic traveling wave solutions and by period-averaging the conservation laws of the NLS equation. The resulting Whitham modulation equations are written in vector form, which allows one to show that they preserve the rotational invariance of the NLS equation, as well as the invariance with respect to scaling and Galilean transformations, and to immediately generalize the calculations from two spatial dimensions to three. The transformation to Riemann-type variables is described in detail; the harmonic and soliton limits of the Whitham modulation equations are explicitly written down; and the reduction of the Whitham equations to those for the radial NLS equation is explicitly carried out. Finally, the extension of the theory to higher spatial dimensions is briefly outlined. The multidimensional NLS-Whitham equations obtained here may be used to study large amplitude wavetrains in a variety of applications including nonlinear photonics and matter waves.

Group-theoretic approach to perfect fluid equations with conformal symmetry

The method of nonlinear realizations is a convenient tool for building dynamical realizations of a Lie group, which relies solely upon structure relations of the corresponding Lie algebra. The goal of this work is to discuss advantages and limitations of the method, which is here applied to construct perfect fluid equations with conformal symmetry. Four cases are studied in detail, which include the Schrodinger group, the l-conformal Galilei group, the Lifshitz group, and the relativistic conformal group.

Invariance of the acoustic wave equation under transformed Galilean transformation

Invariance of the acoustic wave equation under transformed Galilean transformation

Stewart’s Theorem and Median Property in the Galilean Plane

Galilean geometry can be introduced in the affine plane, as in Euclidean geometry. The difference between Euclidean geometry and Galilean geometry is that the distance function. Thus, we can compare the many theorems and properties which is included the concept of distance in these geometries. Therefore, in this study, we give the Galilean analogues of Stewart’s theorem and median property.