Dipole radiation and beyond from axion stars in electromagnetic fields

We investigate the production of photons from coherently oscillating, spatially localized clumps of axionic fields (oscillons and axion stars) in the presence of external electromagnetic fields. We delineate different qualitative behaviour of the photon luminosity in terms of an effective dimensionless coupling parameter constructed out of the axion-photon coupling, and field amplitude, oscillation frequency and radius of the axion star. For small values of this dimensionless coupling, we provide a general analytic formula for the dipole radiation field and the photon luminosity per solid angle, including a strong dependence on the radius of the configuration. For moderate to large coupling, we report on a non-monotonic behavior of the luminosity with the coupling strength in the presence of external magnetic fields. After an initial rise in luminosity with the coupling strength, we see a suppression (by an order of magnitude or more compared to the dipole radiation approximation) at moderately large coupling. At sufficiently large coupling, we find a transition to a regime of exponential growth of the luminosity due to parametric resonance. We carry out 3+1 dimensional lattice simulations of axion electrodynamics, at small and large coupling, including non-perturbative effects of parametric resonance as well as backreaction effects when necessary. We also discuss medium (plasma) effects that lead to resonant axion to photon conversion, relevance of the coherence of the soliton, and implications of our results in astrophysical and cosmological settings.

Two-point function of the energy-momentum tensor and generalised conformal structure

Theories with generalised conformal structure contain a dimensionful parameter, which appears as an overall multiplicative factor in the action. Examples of such theories are gauge theories coupled to massless scalars and fermions with Yukawa interactions and quartic couplings for the scalars in spacetime dimensions other than 4. Many properties of such theories are similar to that of conformal field theories (CFT), and in particular their 2-point functions take the same form as in CFT but with the normalisation constant now replaced by a function of the effective dimensionless coupling g constructed from the dimensionful parameter and the distance separating the two operators. Such theories appear in holographic dualities involving non-conformal branes and this behaviour of the correlators has already been observed at strong coupling. Here we present a perturbative computation of the two-point function of the energy-momentum tensor to two loops in dimensions $$d= 3, 5$$ d = 3 , 5 , confirming the expected structure and determining the corresponding functions of g to this order, including the effects of renormalisation. We also discuss the $$\hbox {d}=4$$ d = 4 case for comparison. The results for $$d=3$$ d = 3 are relevant for holographic cosmology, and in this case we also study the effect of a $$\Phi ^6$$ Φ 6 coupling, which while marginal in the usual sense it is irrelevant from the perspective of the generalised conformal structure. Indeed, the effect of such coupling in the 2-point function is washed out in the IR but it modifies the UV.

Solving the 2D SUSY Gross-Neveu-Yukawa model with conformal truncation

We use Lightcone Conformal Truncation to analyze the RG flow of the two-dimensional supersymmetric Gross-Neveu-Yukawa theory, i.e. the theory of a real scalar superfield with a ℤ2-symmetric cubic superpotential, aka the 2d Wess-Zumino model. The theory depends on a single dimensionless coupling $$ \overline{g} $$ g ¯ , and is expected to have a critical point at a tuned value $$ {\overline{g}}_{\ast } $$ g ¯ ∗ where it flows in the IR to the Tricritical Ising Model (TIM); the theory spontaneously breaks the ℤ2 symmetry on one side of this phase transition, and breaks SUSY on the other side. We calculate the spectrum of energies as a function of $$ \overline{g} $$ g ¯ and see the gap close as the critical point is approached, and numerically read off the critical exponent ν in TIM. Beyond the critical point, the gap remains nearly zero, in agreement with the expectation of a massless Goldstino. We also study spectral functions of local operators on both sides of the phase transition and compare to analytic predictions where possible. In particular, we use the Zamolodchikov C-function to map the entire phase diagram of the theory. Crucial to this analysis is the fact that our truncation is able to preserve supersymmetry sufficiently to avoid any additional fine tuning.

Coupling synchronization principle of two pairs counter-rotating unbalanced rotors in the different resonant conditions

The present work investigates the coupling synchronization principle and stability in a vibrating system with two pairs counter-rotating unbalanced rotors (also called exciters). Based on Lagrange equations, the dimensionless coupling differential equations of motion of the system are deduced. The synchronization criterion of two pairs exciters stems from the averaging method, it satisfies the fact that the absolute value of dimensionless residual torque difference between arbitrary two driving motors is less than or equal to the maximum of their dimensionless coupling torques. The stability criterion of the synchronous states complies with Routh-Hurwitz principle. The coupling dynamic characteristics of the system are numerically analyzed in detail, including synchronization and stability ability, maximum of the coupling torque and phase relationship, etc. Some simulation results applying the Runge-Kutta algorithm are performed, it is shown that the motion states of the system can be classified into two types: sub-resonant state and super-resonant state. Generally in engineering, the ideal working points should be selected in sub-resonance region, in this case the expended energy can be saved relatively by 1/5–1/3, which is less than that in super-resonance region under the precondition of the same vibration amplitude value.

Supergraph calculation of one-loop divergences in higher-derivative 6D SYM theory

We apply the harmonic superspace approach for calculating the divergent part of the one-loop effective action of renormalizable 6D, $$ \mathcal{N} $$ N = (1, 0) supersymmetric higher-derivative gauge theory with a dimensionless coupling constant. Our consideration uses the background superfield method allowing to carry out the analysis of the effective action in a manifestly gauge covariant and $$ \mathcal{N} $$ N = (1, 0) supersymmetric way. We exploit the regularization by dimensional reduction, in which the divergences are absorbed into a renormalization of the coupling constant. Having the expression for the one-loop divergences, we calculate the relevant β-function. Its sign is specified by the overall sign of the classical action which in higher-derivative theories is not fixed a priori. The result agrees with the earlier calculations in the component approach. The superfield calculation is simpler and provides possibilities for various generalizations.

Dynamics and the emergence of geometry in an information mesh

The idea of a graph theoretical approach to modeling the emergence of a quantized geometry and consequently spacetime, has been proposed previously, but not well studied. In most approaches the focus has been upon how to generate a spacetime that possesses properties that would be desirable at the continuum limit, and the question of how to model matter and its dynamics has not been directly addressed. Recent advances in network science have yielded new approaches to the mechanism by which spacetime can emerge as the ground state of a simple Hamiltonian, based upon a multi-dimensional Ising model with one dimensionless coupling constant. Extensions to this model have been proposed that improve the ground state geometry, but they require additional coupling constants. In this paper we conduct an extensive exploration of the graph properties of the ground states of these models, and a simplification requiring only one coupling constant. We demonstrate that the simplification is effective at producing an acceptable ground state. Moreover we propose a scheme for the inclusion of matter and dynamics as excitations above the ground state of the simplified Hamiltonian. Intriguingly, enforcing locality has the consequence of reproducing the free non-relativistic dynamics of a quantum particle.

Energy transfer from spacetime into matter and a bouncing inflation from covariant canonical gauge theory of gravity

Cosmological solutions for covariant canonical gauge theories of gravity are presented. The underlying covariant canonical transformation framework invokes a dynamical spacetime Hamiltonian consisting of the Einstein–Hilbert term plus a quadratic Riemann tensor invariant with a fundamental dimensionless coupling constant [Formula: see text]. A typical time scale related to this constant, [Formula: see text], is characteristic for the type of cosmological solutions: for [Formula: see text], the quadratic term is dominant, the energy–momentum tensor of matter is not covariantly conserved, and we observe modified dynamics of matter and spacetime. On the other hand, for [Formula: see text], the Einstein term dominates and the solution converges to classical cosmology. This is analyzed for different types of matter and dark energy with a constant equation of state. While for a radiation-dominated universe solution, the cosmology does not change, we find for a dark energy universe the well-known de-Sitter space. However, we also identify a special bouncing solution (for [Formula: see text]) which for large times approaches the de-Sitter space again. For a dust-dominated universe (with no pressure), deviations are seen only in the early epoch. In late epoch, the solution asymptotically behaves as the standard dust solution.

Investigations on stability of the synchronous states for three homodromy exciters in the vibrating system with double resonant types

This paper investigates stability of the synchronous states for three homodromy exciters in the vibrating system, some theoretical analyses and simulation results on which are given. Based on Lagrange equations, the differential equations of motion of the system are obtained. Using the average method yields the dimensionless coupling torque balanced equations of three exciters and the simplified analytical expressions for synchronization criterion of the system are deduced, the stability criterion of the synchronous states complies with Routh–Hurwitz principle. The dynamic characteristics of the system for different frequency ratios are discussed numerically. In order to verify the validity of theoretical methods, the simulation results by a Runge–Kutta routine are carried out; it indicates that the motion state of the vibrating system can be classified into two types: sub-resonant state and super-resonant state. The motion type of the rigid frame is strong positive superposition vibration in a sub-resonant state; while in a super-resonant state, the exciting forces of three exciters are mutually cancelled and the rigid frame is motionless. During the design process of the vibrating machines, the ideal working points are only selected in a sub-resonant state, which makes the vibrating machines work efficiently.

Reconstructed anisotropic models in F(T, TG) gravity

We explore the reconstruction scenario of a spatially homogenous and anisotropic universe model in the framework of F(T, TG) gravity (T represents the torsion scalar and TG is the teleparallel equivalent of the Gauss–Bonnet term). We construct F(T, TG) models by assuming different phases of the universe, like a dark energy dominated era, non-relativistic as well as relativistic matter eras, and their combinations. The graphical behavior of these models indicates a decreasing pattern for ω = −1 and its combination with ω = 0 and 1/3. Finally, we evaluate the equation of state parameter by considering the F(T, TG) model and study its evolutionary behavior for particular values of dimensionless coupling parameters.

Design method of dynamic parameters of a self-synchronization vibrating system with dual mass

This paper presents a design method of dynamic parameters for the self-synchronization vibrating conveyor with two exciters. The dimensionless coupling equations of the two exciters are derived by using the average method of modified small parameters and the synchronization and stability criteria are deduced from the existence and stability conditions of the dimensionless coupling equations. The two exciters loading coefficient is a periodic function of the phase difference between the two exciters and the extreme point of synchronization is either the minimum or maximum point of the two exciters loading coefficient. There are two ridges in the three-dimensional graphs of the characteristic amplitude and the force transmission coefficient on the plane of the two design frequency ratios, respectively. One ridge of both the characteristic amplitude and the force transmission coefficient is distributed along the curve segment of the one natural frequency ratio in the direction of the working mass frequency ratio approaching to zero, but the other ridge of the characteristic amplitude and that of the force transmission coefficient go along the curve segments of the other natural frequency ratio in the directions that the isolation mass frequency ratio and the working mass frequency ratio approach to infinity, respectively. The design procedure of the dynamic parameters is proposed by numerically and experimentally discussing the effects of the dynamic parameters on the performance parameters of vibrating system. A design example of the vibrating conveyor is given to verify the effectiveness of the proposed design method.