Search Results (10)

Based on the thermal phase structure of pure SU(2) quantum Yang–Mills theory, we describe the electron at rest as an extended particle, a droplet of radius $r_0\sim a_0$, where $a_0$ is the Bohr radius. This droplet is of vanishing pressure and traps a monopole within its bulk at a temperature of $T_c=7.95$ keV. The monopole is in the Bogomolny–Prasad–Sommerfield (BPS) limit. It is interpreted in an electric–magnetically dual way. Utilizing a spherical mirror-charge construction, we approximate the droplet’s charge at a value of the electromagnetic fine-structure constant $\alpha$ of ${\alpha }^{-1}\sim 134$ for soft external probes. It is shown that the droplet does not exhibit an electric dipole or quadrupole moment due to averages of its far-field electric potential over monopole positions. We also calculate the mixing angle ${\theta }_{\mathrm{W}}\sim 30°$, which belongs to deconfining phases of two SU(2) gauge theories of very distinct Yang–Mills scales (${\Lambda }_{\mathrm{e}}=3.6$ keV and ${\Lambda }_{\mathrm{CMB}}\sim {10}^{-4}$ eV). Here, the condition that the droplet’s bulk thermodynamics is stable determines the value of ${\theta }_W$. The core radius of the monopole, whose inverse equals the droplet’s mass in natural units, is about 1% of $r_0$. Full article

Here, we report the results of a Mössbauer study on hyperfine electrical and magnetic interactions in quadruple perovskite BiMn₇O₁₂ doped with ⁵⁷Fe probes. Measurements were performed in the temperature range of 10 K < T < 670 K, wherein BiMn_6.96⁵⁷Fe_0.04O₁₂ undergoes a cascade of structural (T₁ ≈ 590 K, T₂ ≈ 442 K, and T₃ ≈ 240 K) and magnetic (T_N1 ≈ 57 K, T_N2 ≈ 50 K, and T_N3 ≈ 24 K) phase transitions. The analysis of the electric field gradient (EFG) parameters, including the dipole contribution from Bi³⁺ ions, confirmed the presence of the local dipole moments p_Bi, which are randomly oriented in the paraelectric cubic phase (T > T₁). The unusual behavior of the parameters of hyperfine interactions between T₁ and T₂ was attributed to the dynamic Jahn–Teller effect that leads to the softening of the orbital mode of Mn³⁺ ions. The parameters of the hyperfine interactions of ⁵⁷Fe in the phases with non-zero spontaneous electrical polarization (P_s), including the P1 ↔ Im transition at T₃, were analyzed. On the basis of the structural data and the quadrupole splitting Δ(T) derived from the ⁵⁷Fe Mössbauer spectra, the algorithm, based on the Born effective charge model, is proposed to describe P_s(T) dependence. The P_s(T) dependence around the Im ↔ I2/m phase transition at T₂ is analyzed using the effective field approach. Possible reasons for the complex relaxation behavior of the spectra in the magnetically ordered states (T < T_N1) are also discussed. Full article

The orientation and magnitude of the molecular electric dipole moment are key properties relevant to topics ranging from the nature of intermolecular interactions to the quantitative analysis of complex gas-phase mixtures, such as chemistry in astrophysical environments. Stark effect measurements on rotational spectra have been the method of choice for isolated molecules but have become less common with the practical disappearance of Stark modulation spectrometers. Their role has been taken over by supersonic expansion measurements within a Fabry-Perot resonator cavity, which introduces specific technical problems that need to be overcome. Several of the adopted solutions are described and compared. Presently, we report precise electric dipole moment determinations for the two most stable conformers of the selected molecules of confirmed or potential astrophysical relevance: n-propanol, n-butanol, and n-butyl cyanide. All dipole moment components have been precisely determined at supersonic expansion conditions by employing specially designed Stark electrodes and a computer program for fitting the measured Stark shifts, inclusive of cases with resolved nuclear quadrupole hyperfine structure. The experimental values are compared with suitable quantum chemistry computations. It is found that, among the tested levels of computation, vibrationally averaged dipole moments are the closest to the observation and the molecular values are, as in the lighter molecules in the series, largely determined by the hydroxyl or nitrile groups. Full article

Dynamical symmetry plays a dominant role in the interacting boson model in elucidating nuclear structure, for which group theoretical or algebraic techniques are powerful. In this work, the higher-order interactions required in describing triaxial deformation in the interacting boson model are introduced to improve the fitting results to low-lying level energies, $B(E2)$ values and electric quadrupole moments of even–even nuclei. As an example of the model application, the low-lying excitation spectra and the electromagnetic transitional properties of even–even ^176−198Pt are fitted and compared to the experimental data and the results of the consistent-Q formalism. It is shown that the results obtained from the model are better than those of the original consistent-Q formalism, indicating the importance of the higher-order interactions in describing the structure and the shape phase evolution of these nuclei. Full article

The particle-rotor-quadrupole-coupling model, in which the quadrupole–quadrupole interaction of the even-even core is described by a triaxial rotor with a single-j particle, is adopted to describe low-lying spectra of odd-A nuclei within the vibrational to triaxial transition region. In contrast to the particle-plus-rotor-model, the quadrupole–quadrupole interaction introduced in the particle-rotor-quadrupole-coupling model keeps the rotational symmetry in the collective model framework without approximation. To demonstrate the usability, low-lying level energies, reduced E2 transition probabilities, and ground-state quadrupole moments of ¹³⁵Ba and ¹³¹Xe are fit by the model, of which the results are compared with the experimental data and those of other models. It is shown that the fitting results of the particle-rotor-quadrupole-coupling model to the low-lying level energies, reduced E2 transition probabilities, and ground-state electric quadrupole moments of ¹³⁵Ba and ¹³¹Xe are the best, of which the model parameters of the even-even core are determined by the triaxial rotor model in fitting the low-lying spectra of ¹³⁴Ba and ¹³⁰Xe. In comparison with the E(5/4) model results of ¹³⁵Ba, it is also shown that the quadrupole–quadrupole interaction of the even-even core with the single particle adopted can indeed reproduce the E(5/4) critical point behavior. The fitting quality of the reduced E2 transition probabilities among low-lying states by the particle-rotor-quadrupole-coupling model is also noticeably improved. Thus, it can be concluded that the particle-rotor-quadrupole-coupling model is suitable to describe low-lying properties of odd-A nuclei within the transitional region. Full article

The energy levels arising from the electronic orbital $5p-4f$ crossing between the ground $5p^{2}4f$ and excited $5p4f^2$ configurations in the Nd${}^{9+}$ ion are investigated by using high-accuracy relativistic ab initio calculations. The accurate atomic data of the lifetime, $g_J$ factor, electric quadrupole moment, and hyperfine structure of the magnetic dipole are also presented. The long-lived states that are suitable for making narrow-linewidth (milli-Hz) clock lines are found. Dominant systematics caused by stray electromagnetic interactions in an experiment and the coefficients of the relativistic sensitivityto variation of the fine-structure constant $\alpha$ and of the Lorentz invariance violation are evaluated, thus validating that the Nd${}^{9+}$ ion can be a new candidate for high-resolution spectroscopy and precision fundamental studies for probing new physics beyond the Standard Model. Full article

Within the framework of the light-cone QCD sum rules method (LCSR’s), the radiative $\Delta \left(1600\right)\to \gamma N$ decay is studied. In particular, the magnetic dipole moment $G_M^1\left(0\right)$ and the electric quadrupole moment $G_E^1\left(0\right)$ are estimated. We also calculate the ratio $R_{EM}=-\frac{G_E^1\left(0\right)}{G_M^1\left(0\right)}$ and the decay rate. The predicted multipole moments and the decay rate strongly agree with the existing experimental results as well as with the other available phenomenological approaches. Full article

Molecular quantum electrodynamics (QED) theory is employed to calculate the rate of resonance energy transfer (RET) between a donor, D, described by an electric dipole and quadrupole, and magnetic dipole coupling, and an identical acceptor molecule, A, that is mediated by a third body, T, which is otherwise inert. A single virtual photon propagates between D and T, and between T and A. Time-dependent perturbation theory is used to compute the matrix element, from which the transfer rate is evaluated using the Fermi golden rule. This extends previous studies that were limited to the electric dipole approximation only and admits the possibility of the exchange of excitation between a chiral emitter and absorber. Rate terms are computed for specific pure and mixed multipole-dependent contributions of D and A for both an oriented arrangement of the three particles and for the freely tumbling situation. Mixed multipole moment contributions, such as those involving electric–magnetic dipole or electric dipole–quadrupole coupling at one center, do not survive random orientational averaging. Interestingly, the mixed electric–magnetic dipole D and A rate term is non-vanishing and discriminatory, exhibiting a dependence on the chirality of the emitter and absorber, and is entirely retarded. It vanishes, however, if D and A are oriented perpendicularly to one another. Near- and far-zone asymptotes of isotropic contributions to the rate are also evaluated, demonstrating radiationless short-range transfer and inverse-square radiative exchange at very large separations. Full article

Utilizing the tools of tendex and vortex, we study the highly dynamic plunge and merger phases of several $\pi$ -symmetric binary black hole coalescences. In particular, we observe a decline of the strength of the current quadrupole moment compared to that of the mass quadrupole moment during the merger phase, contrary to a naive estimate according to the dependence of these moments on the separation between the black holes. We further show that this decline of the current quadrupole moment is achieved through the remnants of the two individual spins becoming nearly aligned or anti-aligned with the total angular momentum. We also speculate on the ability to achieve a consistency between the electric and magnetic parity quasinormal modes. Full article

The present work is devoted to the study of the electric properties: electric dipole moment, electric quadrupole moment, electric field gradients and electric dipole polarizability of molecule Zr₂Fe on base of the full relativistic theory with basis set 3–21G. The electric dipole moment of Zr₂Fe is symmetrical to the axis of $C_{2V}$ —the vector sum of two projections for two chemical bond FeZr (3.2883 Å), based on when there is charge distribution. The force constant $k_2$ is directly connected with electric field gradients. Full article