Energy Density Of Field Research Articles

Large plasmonic field enhancement on hydrogen-absorbing transition metals at lower frequencies: Implications for hydrogen storage, sensing, and nuclear fusion

The plasmonic enhancement of electromagnetic field energy density around planar surfaces of hydrogen-absorbing transition metals, Pd, Ti, and Ni, has been quantitatively investigated, to explore the use of plasmonics in the forthcoming hydrogen economy. We have observed that a large degree of energy focusing, with the enhancement factor over several hundreds, is available for these transition metals in the microwave region, even surpassing the enhancement for noble metals. This finding could potentially lead to technological progress in various hydrogen-related energy applications including hydrogen storage, sensing, and nuclear fusion.

A reassessment of the multiaxial ductility C* creep crack growth equation based on the strain energy integral of the HRR singular field terms

A revaluation of the upper bound plane strain multiaxial C* crack growth rates is undertaken for a range of materials. The analysis assumes that the multiaxial ductility factor can be approximated by taking the integrated dimensionless deviatoric and hydrostatic strain energy density of the HRR singular fields. Using the equivalency approximation between the plastic and elastic strain energy, a damage mechanics approach is used to determine the crack tip triaxial constraint. The new multiaxial factor was found to be independent of the power law behaviour, and for plane stress HRR fields gave a multiaxial factor of close to one. The new factor enables estimates of the upper bound crack rates under plane strain in the Nikbin Smith Webster equation to be undertaken. Creep crack growth data from nine materials were used to assess the new approximation for upper bound crack growth rates. The results suggest the current upper bound plane strain crack growth rates could be decreased from the current thirty times to three times the plane stress results for a range of materials.

Dark matter as scalaron in f(R) gravity models

We explore the scalar field obtained under the conformal transformation of the spacetime metric $g_{\mu\nu}$ from the Jordan frame to the Einstein frame in $f(R)$ gravity. This scalar field is the result of the modification in the gravitational part of the Einstein's general relativistic theory of gravity. For $f(R)=\frac{R^{1+\delta}}{R_{c}^{\delta}}$, we find the effective potential of the scalar field and calculate the mass of the scalar field particle scalaron. It is shown that the mass of the scalaron depends upon the energy density of standard matter in the background. The interaction between standard matter and scalaron is weak in the high curvature regime. This linkage between the mass of the scalaron and the background leads to the physical effects of dark matter and is expected to reflect the anisotropic propagation of scalaron in moving baryonic matter fields as in merging clusters (Bullet cluster, the Abell 520 system, MACS etc.). Such scenario also satisfies the local gravity constraints of $f(R)$ gravity. We further calculate the equation of state of the scalar field in the action-angle variable formalism and show its distinct features as the dark matter and dark energy with respect to energy density of the scalar field at different values of the model parameter $\delta$.

Optical electrostriction pressure in liquid, solids and gases

The electrostriction pressure is accompanied by the compression of the body located in an electrical field. As a result, a part of the energy of the electrical field is transferred into the elastic energy connected with the compression of the body. There is a minimum of the total energy at a steady state. We calculate the minimum and determine a magnitude of the compression and the pressure responsible for the compression. The pressure is equal to the electrostriction pressure. It turn out that the well-known expression for the electrostriction pressure is valid for liquid and solids on assumption that a change of their volumes is negligible small. This expression is not valid for gases. There is a threshold of the energy density of the electrical field, below which the electrostriction pressure is absent. The threshold for the atmosphere air at normal conditions is about 7.4 107 J/m3.

Schwinger mechanism during inflation

We revisit the efficiency of Schwinger mechanism in creating charged pairs during inflation. We consider a minimal setup of inflation in which the inflaton field is a complex scalar field charged under a $U(1)$ gauge field. There is a time dependent conformal coupling which pumps energy from the inflaton field to the gauge field to furnish a nearly constant background electric field energy density to drive the Schwinger mechanism. The coupling between the gauge field and the scalar field induces a time dependent effective mass for the inflaton field. The requirement of a long period of slow-roll inflation causes the Schwinger mechanism to be highly inefficient during inflation. The non-perturbative Schwinger mechanism can be relevant only towards the end of inflation and only on very small scales. This is in contrast to hypothetical models studied in literature in which the complex scalar field is a test field and a constant electric field is imposed on the dS background by hand. We calculate the number of pairs of charged particles created perturbatively during inflation. We show that it is proportional to the amplitude of the quadrupolar statistical anisotropy and it is very small. Consequently, the back-reactions of created particles on magnetogenesis on large scales are negligible.

Temporal correlation between the optical and γ-ray flux variations in the blazar 3C 454.3

ABSTRACT Blazars show optical and γ-ray flux variations that are generally correlated, although there are exceptions. Here we present anomalous behaviour seen in the blazar 3C 454.3 based on an analysis of quasi-simultaneous data at optical, ultraviolet, X-ray, and γ-ray energies, spanning about 9 yr from 2008 August to 2017 February. We have identified four time intervals (epochs), A, B, D, and E, when the source showed large-amplitude optical flares. In epochs A and B the optical and γ-ray flares are correlated, while in D and E corresponding flares in γ-rays are weak or absent. In epoch B the degree of optical polarization strongly correlates with changes in optical flux during a short-duration optical flare superimposed on one of long duration. In epoch E the optical flux and degree of polarization are anticorrelated during both the rising and declining phases of the optical flare. We carried out broad-band spectral energy distribution (SED) modelling of the source for the flaring epochs A,B, D, and E, and a quiescent epoch, C. Our SED modelling indicates that optical flares with absent or weak corresponding γ-ray flares in epochs D and E could arise from changes in a combination of parameters, such as the bulk Lorentz factor, magnetic field, and electron energy density, or be due to changes in the location of the γ-ray-emitting regions.

Vector dark matter production at the end of inflation

It has been shown that the longitudinal mode of a massive vector boson can be produced by inflationary fluctuations and account for the dark matter content of the Universe. In this work we examine the possibility of instead producing the transverse mode via the coupling ϕ F ̃ F between the inflaton and the vector field strength. Such a coupling leads to a tachyonic instability and exponential production of one transverse polarization of the vector field, reaching its maximum near the end of inflation. At production the mass is negligible and the vectors add up coherently to form a dark electromagnetic field. As the Universe expands, the energy density of the dark electromagnetic field then redshifts like radiation until its wavelength stretches to beyond its Compton wavelength. After this point the vectors become non-relativistic and their energy density redshifts like matter. We show that these polarized transverse vectors can account for the observed dark matter relic density in the mass range μeV to hundreds of GeV. We also find that the tachyonic production mechanism of the transverse mode can accommodate larger vector masses and lower Hubble scales of inflation compared to the production mechanism for the longitudinal mode via inflationary fluctuations.

Global Simulations of Protoplanetary Disk Outflows with Coupled Non-ideal Magnetohydrodynamics and Consistent Thermochemistry

Abstract Magnetized winds may be important in dispersing protoplanetary disks and influencing planet formation. We carry out global magnetohydrodynamic simulations in axisymmetry, coupled with ray-tracing radiative transfer, consistent thermochemistry, and non-ideal MHD diffusivities. Magnetized models lacking EUV photons ( ) feature warm molecular outflows that have typical poloidal speeds . When the magnetization is sufficient to drive accretion rates , the wind mass-loss rate is comparable. Such outflows are driven not centrifugally but by the pressure of toroidal magnetic fields produced by bending the poloidal field. Both the accretion and outflow rates increase with the poloidal field energy density, the former almost linearly. The mass-loss rate is also strongly affected by ionization due to UV and X-ray radiation near the wind base. Adding EUV irradiation to the system heats, ionizes, and accelerates the part of the outflow nearest the symmetry axis, but reduces the overall mass-loss rate by exerting pressure on the wind base. Most of our models are non-turbulent, but some with reduced dust abundance and therefore higher ionization fractions exhibit magnetorotational instabilities near the base of the wind.

Hamiltonian analysis of mimetic scalar gravity revisited

We perform the Hamiltonian analysis of several mimetic gravity models and compare our results with those obtained previously by different authors. We verify that for healthy mimetic scalar-tensor theories the condition for the corresponding part of the Hamiltonian to be bounded from below is the positive value of the mimetic field energy density $\lambda$. We show that for mimetic dark matter possessing a shift symmetry the mimetic energy density remains positive in time, provided appropriate boundary conditions are imposed on its initial value, while in models without shift symmetry the positive energy density can be maintained by simply replacing $\lambda\to e^{\lambda}$. The same result also applies to mimetic $f(R)$ gravity, which is healthy if the usual stability conditions of the standard $f(R)$ gravity are assumed and $\lambda>0$. In contrast, if we add mimetic matter to an unhealthy seed action, the resulting mimetic gravity theory remains, in general, unstable. As an example, we consider a scalar-tensor theory with the higher-derivative term $(\Box \varphi)^2$, which contains an Ostrogradski ghost. We also revisit results regarding stability issues of linear perturbations around the FLRW background of the mimetic dark matter in the presence of ordinary scalar matter. We find that the presence of conventional matter does not revive dynamical ghost modes (at least in the UV limit). The modes, whose Hamiltonian is not positive definite, are non-propagating (have zero sound speed) and are associated with the mimetic matter itself. They are already present in the case in which the ordinary scalar fluid is absent, causing a growth of dust overdensity.

The twisted gradient flow coupling at one loop

We compute the one-loop running of the SU(N) ’t Hooft coupof twelve-flavor SU(3) gauge theoryling in a finite volume gradient flow scheme using twisted boundary conditions. The coupling is defined in terms of the energy density of the gradient flow fields at a scale tilde{l} given by an adequate combination of the torus size and the rank of the gauge group, and is computed in the continuum using dimensional regularization. We present the strategy to regulate the divergences for a generic twist tensor, and determine the matching to the overline{mathrm{MS}} scheme at one-loop order. For the particular case in which the twist tensor is non-trivial in a single plane, we evaluate the matching coefficient numerically and determine the ratio of Λ parameters between the two schemes. We analyze the N dependence of the results and the possible implications for non-commutative gauge theories and volume independence.

Spatiotemporal Analysis of an Efficient Fresnel Grating Coupler for Focusing Surface Plasmon Polaritons

Time-resolved photoemission microscopy is used to investigate the spatiotemporal properties of surface plasmon polaritons launched at a Fresnel-type grating coupler. By milling a multiline structure of segmented grooves with dimensions derived from Fresnel zones into a plasmonic material, efficient focusing of surface plasmon polaritons can be accomplished. We demonstrate the presence of pulse broadening at the focus associated with propagation delays in the device. Moreover, our experimental data implies an enhancement of the plasmonic field energy density at the focus in excess of a factor of 10, with a focal spot size at the Abbe limit for our lens.

Noncommutativity in Effective Loop Quantum Cosmology

We construct a noncommutative extension of the Loop Quantum Cosmology effective scheme for the flat FLRW model with a free scalar field via a theta deformation. Firstly, a deformation is implemented in the configuration sector, among the holonomy variable and the matter degree of freedom. We show that this type of noncommutativity retains, to some degree, key features of the Loop Quantum Cosmology paradigm for a free field. Secondly, a deformation is implemented in the momentum sector, among the momentum associated with the holonomy variable and the momentum associated with the matter field. We show that in this latter case the scalar field energy density is the same as the one in standard Loop Quantum Cosmology.

Effects of the Gravitational Interaction of a Scalar Field and Magnetic and Electric Vortex Fields

The combined action of self-gravitating magnetic and electric vortex fields and a self-gravitating scalar field is considered. The properties of wormholes formed as a result of such an interaction are investigated. It is shown that a change in the energy density of a massless scalar field can modify the topology of spacetime for the system of self-gravitating fields under consideration.

Acoustofluidic particle steering.

Steering micro-objects using acoustic radiation forces is challenging for several reasons: resonators tend to create fixed force distributions that depend primarily on device geometry, and even when using switching schemes, the forces are hard to predict a priori. In this paper an active approach is developed that measures forces from a range of acoustic resonances during manipulation using a computer controlled feedback loop based in matlab, with a microscope camera for particle imaging. The arrangement uses a planar resonator where the axial radiation force is used to hold particles within a levitation plane. Manipulation is achieved by summing the levitation frequency with an algorithmically chosen second resonance frequency, which creates lateral forces derived from gradients in the kinetic energy density of the acoustic field. Apart from identifying likely resonances, the system does not require a priori knowledge of the structure of the acoustic force field created by each resonance. Manipulation of 10 μm microbeads is demonstrated over 100 s μm. Manipulation times are of order 10 s for paths of 200 μm length. The microfluidic device used in this work is a rectangular glass capillary with a 6 mm wide and 300 μm high fluid chamber.

Relating Eccentricity Fluctuations to Density Fluctuations in Heavy-ion Collisions

The magnitude of anisotropic flow in a nucleus-nucleus collision is determined by the energy density field, $\rho(x,y,z)$, created right after the collision occurs. Specifically, elliptic flow, $v_2$, and triangular flow, $v_3$, are proportional to the anisotropy coefficients $\varepsilon_2$ and $\varepsilon_3$, which are functionals of $\rho$. We express the mean and the variance of $\varepsilon_2$ and $\varepsilon_3$ as a function of the 1- and 2-point functions of $\rho$. These results generalize results obtained previously, that were valid only for central collisions, or only for identical point-like sources. We apply them to the color glass condensate effective theory, using the recently derived expression of the 2-point function.

Soliton-Like Spherical Symmetric Solutions of the Nonlinear Spinor Field Equations Depending on the Invariant Function <i>I<sub>P</sub></i>=<i>P</i><sup>2</sup> in the General Relativity Theory

The present research work is considered as part II of the previous work entitled [Plane Symmetric Solutions to the Nonlinear Spinor Field Equations in General Relativity Theory, jmp, 2019, 10, 1222-1234]. Here, we opt for the static spherical symmetric metric. In this metric, we have obtained spherical symmetric soliton-like solutions to the spinor field equations with nonlinear terms, which are arbitrary functions of , taking into account the proper gravitational field of elementary particles. Equations with power and polynomial nonlinearities are investigated in detail. It is shown that the initial set of the Einstein and spinor field equations with a power-law nonlinearity possess regular solutions with a localized energy density of the spinor field only if we consider massless particle without losing the generality (m = 0). In this case, a soliton-like configuration has negative energy. In order to define the role of the nonlinearity and the own gravitational field of the elementary particles in this model, we have obtained exact static symmetric solutions to the above spinor field equations in the linear case by considering Dirac’s equations and in flat space-time. It is proved that soliton-like solutions are absent in the linear case. But in flat space-time soliton-like configurations exist and have positive total energy.

Plane Symmetric Solutions to the Nonlinear Spinor Field Equations in General Relativity Theory

We have obtained exact static plane-symmetric solutions to the spinor field equations with nonlinear terms which are arbitrary functions of invariant , taking into account their own gravitational field. It is shown that the initial set of the Einstein and spinor field equations with a power-law nonlinearity have regular solutions with a localized energy density of the spinor field only if m=0 (m is the mass parameter in the spinor field equations). Equations with power and polynomial nonlinearities are studied in detail. In this case, a soliton-like configuration has negative energy. We have also obtained exact static plane-symmetric solutions to the above spinor field equations in flat space-time. It is proved that in this case soliton-like solutions are absent.

Дираковская звезда с дипольным магнитным полем

Compact gravitating configurations consisting of strongly magnetized spinor fluid are studied. The latter is described by an effective equation of state which is obtained in the limit of large values of the coupling constant of a nonlinear spinor field. Regular static asymptotically flat solutions describing configurations with finite sizes (Dirac stars) are found. Mass-radius relations for stars with masses of the order of the Chandrasekhar mass and radii comparable with sizes of neutron stars are constructed. The structure of a dipole magnetic field modeled in the form of an axisymmetric poloidal magnetic field created by toroidal electric currents is investigated. The energy density of the magnetic field is assumed to be much smaller than that of the spinor fluid. The radial and tangential components of the magnetic field strength are computed. It is shown that their distributions along the radius of the configurations are similar to those of neutron stars.

The role of acceleration and vorticity in relativistic hydrodynamics

The role of vorticity and acceleration in relativistic hydrodynamics is investigated. Particular attention is paid to the effects of vorticity, as well as mixed effects, when the medium has both acceleration and vorticity. Quantumfield corrections to the energy density of free Dirac fields are calculated using the Zubarev density operator. The corresponding nonperturbative formulas are proposed and justified in the particular cases of parallel vorticity and acceleration and zero acceleration.

Interface Sensitized Optical Microfiber Biosensors

Sensitivity is an important parameter to characterize the performance of sensors. Interfacial modification and functionalization is an effective strategy to improve the sensitivity of optical biosensors. This paper reports our recent development on interface sensitized fiber optic biosensors for the detection of ultra-low concentration of biological targets. We employ microfiber mode interferometer as transducer to sense the molecular binding interaction induced surrounding refractive index change. By modifying the microfiber surface to increase the assembling surface area and enhance the evanescent field energy density, ultra-low limit of detection of 1.65 × 10−15 M and 6.82 × 10−17 M, respectively, were realized for neurotransmitter γ-amino-butyric acid and cellular cytochrome c.