Narrow Results

In this work, using a description of defects in solids in terms of three-dimensional gravity, we have obtained the changes on the spectrum energy and eigenfunctions of a bound particle, moving in a magnetic field, in a space with a linear topological defect, namely disclination and screw dislocation. We find exact expressions for the energy eigenvalue and eigenfunctions and compare these results with the ones obtained in the previous cases.

The present situation and hopes on bounding (founding) neutrino magnetic moment in future are reviewed.

We discuss the observational effects of the direct coupling of neutrino magnetic moment with electromagnetic field through Pauli interaction in extreme conditions. We calculate the neutrino pair creation rate from the instability of the strong magnetic field possibly in the vicinity of astrophysical compact objects and the enhancement of neutrino production rates in the high energy collider experiments as well as in the high energy cosmic ray experiments.

The static properties of protons are useful for understanding the quark structure of the proton. In his work we have introduced the hypercentral constituent quark model and isospin dependent potentials. Here constituent quarks interact with each other via a potential in which we have taken into account the three-body force effect and the standard two-body potential contributions. According to our model the static properties of protons containing u and d quarks are better than the other models and closer to experimental results. The two key ingredients of this improvement are the effective quark–gluon hypercentral potentials, and hyperfine interaction and isospin dependence potential. Recently, Schrödinger equation has been solved by Giannini but we have solved the Dirac equation exact analytically and we have shown that a considerable improvement in the description of the static properties of proton is obtained with an isospin dependent potential and the complete interaction including spin and isospin terms reproduces the position of the quark.

Existence of non-zero neutrino magnetic moment would mean new physics beyond the standard model. A search for the neutrino magnetic moment has been conducted using the high statistic solar neutrino data from Super-Kamiokande-I. This is done by looking for the distortion to the observed energy spectrum of recoil electrons. A non-zero neutrino magnetic moment would cause an increase of event rates at lower energies. The search found no clear signal of neutrino magnetic moment. A limit on the neutrino magnetic moment has been obtained at 3.6 × 10^-10μ_B at 90% C.L. by fitting to the Super-Kamiokande day-night spectra. The effects of neutrino oscillation have been included in the analysis. Including results from other neutrino experiments limiting the oscillation region, a limit of 1.1 × 10^-10μ_B at 90% C.L. was obtained.

The existence of a neutrino magnetic moment implies contributions to the neutrino mass via radiative corrections. We derive model-independent "naturalness" upper bounds on the magnetic moments of Dirac and Majorana neutrinos, generated by physics above the electroweak scale. For Dirac neutrinos, the bound is several orders of magnitude more stringent than present experimental limits. However, for Majorana neutrinos the magnetic moment bounds are weaker than present experimental limits if μ_ν is generated by new physics at ~ 1 TeV, and surpass current experimental sensitivity only for new physics scales > 10 – 100 TeV. The discovery of a neutrino magnetic moment near present limits would thus signify that neutrinos are Majorana particles.

The vertex function at the limit of small momentum transferred of a virtual massive neutrino in ξ-gauge is calculated via neutrino self-energy operator in a constant electromagnetic field. The expressions for neutrino magnetic moment under various relations between masses of neutrino, W-boson and charged lepton are presented.

Composite nature of a particle can be probed by electromagnetic interactions and information about their structure is embedded in form factors. Most of the experimental and theoretical efforts on baryon electromagnetic form factors have been focused on nucleon while the data on charmed sector are limited to spectroscopy, and weak and strong decays. Forthcoming experiments with a heavy-hadron physics program at major experimental facilities are expected to provide a wealth of information on charmed baryons, which calls for a better understanding of the heavy-sector dynamics from theoretical grounds.

We review the progress in calculating the elastic and transition form factors of charmed baryons in lattice QCD. A collection of static observables, e.g. charge radii, multipole moments, are presented along with the elastic form factors up to $Q^2\sim 1.5{\mathrm{\text{GeV}}}^2$. As one would expect the charmed baryons are compact in comparison to nucleon and this is due to the presence of valence charm quark(s). The elastic and transition magnetic moments are both suppressed. The lattice results provide predictions for the transition magnetic moments, transition and helicity amplitudes and consequentially the decay widths of some singly and doubly charmed baryons.

In general, lattice results are consonant with the qualitative expectations of quark model and heavy-quark symmetry, although there are apparent quantitative differences up to two orders of magnitude in some cases. There are, however, indications that the lattice results can be utilized to improve the model predictions. Nevertheless, discrepancies between the lattice and nonlattice calculations need to be understood better to have a solid insight into the dynamics of the heavy sector.

Furthermore, reliably determined charmed baryon observables would be invaluable input to investigate the nature of exotic states, which further emphasizes the importance of rigorous, first-principles calculations to advance our understanding of the dynamics of the heavy quarks and strong interactions.

Taiji-1’s in-orbit magnetic property is significant for the improvement of the satellite’s attitude-control performance and the acceleration noise model of gravitational reference sensor. Test data of satellite drifts have been used to construct the model including interaction among the magnetic field; remnant magnetic moment and induced magnetic moment so as to estimate the satellite’s magnetic property. Using the global optimization method, the remnant magnetic moment of Taiji-1 is estimated to be (-1.42 -0.19 -0.06) Am².

In this paper, we enumerated ground and excited state masses of singly heavy bottom-strange baryons using the hypercentral constituent quark model (hCQM). The screening potential is used with color-Coulomb potential, as the confining potential. We determine the possible $J^P$ values to recently observed excited states like, ${\mathrm{\Xi }}_b(6100)$, ${\mathrm{\Xi }}_b(6227)$, ${\mathrm{\Xi }}_b(6327)$, ${\mathrm{\Xi }}_b(6333)$ and four ${\mathrm{\Omega }}_b(6316,6330,6340,6350)$ states. The Regge trajectories are plotted in $(J,M^2)$ plane to assign the $J^P$ values and quantum numbers to recently observed states. Using the calculated spectroscopic data, properties such as magnetic moment, transition magnetic moment, radiative decay width, and strong decay width are also investigated for all singly heavy bottom-strange baryonic system.

We study the magnetic moment of leptons in extremely hot universe and superdense media of stars at high temperatures. Anomalous magnetic moment of charged leptons is inversely proportional to its mass, whereas the induced dipole moment of neutral leptons is directly proportional to their mass. Neutral massive point particles exert nonzero magnetic moment as a higher order effect, which is smaller than the anomalous magnetic moment of a charged particle of their same flavor partner. All leptons acquire some extra mass due to their interaction with the medium and affect the magnetic moment accordingly. We compare the contribution to the magnetic moment of various leptons due to their temperature and chemical potential dependent masses. It is shown that the magnetic moment contributions are nonignorable for lighter leptons and heavy neutrinos. These calculations are very important to study the particle propagation in the early universe and in superdense stellar media.

In this paper, we study the properties of triply charm and triply bottom baryon. The mass spectra of these baryons are calculated in nonrelativistic constituent quark model with Coulomb plus screened potential. Several states $S$, $P$, $D$ and $F$ of the ${\mathrm{\Omega }}_{ccc}$ and ${\mathrm{\Omega }}_{bbb}$ baryons with quantum number $J^P={\frac{1}{2}}^{\pm }$, ${\frac{3}{2}}^{\pm }$, ${\frac{5}{2}}^{\pm }$, ${\frac{7}{2}}^{\pm }$ are determined. Regge trajectories are also plotted to determine the quantum number of baryons. Moreover, the magnetic moments are calculated for $J^P={\frac{3}{2}}^{+}$.

Using the Hypercentral Constituent Quark Model (hCQM), the mass spectra of doubly heavy baryons ${\mathrm{\Xi }}_{cb}$ and ${\mathrm{\Xi }}_{bb}$ are determined. The model describes an interaction inside the baryonic system. Screened potential has been considered as confining potential with color-Coulomb potential to enumerate the masses of baryonic states. Regge trajectories have been plotted in $(J,M^2)$ plane. The properties like magnetic moment and radiative decay width have been determined using the obtained results.

The magnetic coupling in pseudomorphic overlayer and sandwich structures of 2ML magnetic ultrathin films on Cu(001) substrate is investigated by using spin-polarized density functional theory. The 2ML magnetic overlayers have significant magnetic moment except CrNi overlayer for which magnetic moment is very small (0.004 μ_B/atom). The overlayers having one layer of Cr turn out to be antiferromagnetically coupled except CrNi/Cu overlayer which has ferromagnetic coupling. All other overlayers have ferromagnetic coupling. In contrast to ferromagnetic MnMn/Cu overlayer, the Cu/MnMn/Cu sandwich has antiferromagnetic coupling. Similar to CrFe/Cu overlayer, the Cu/CrFe/Cu sandwich has antiferromagnetic coupling, while all other sandwiches have ferromagnetic coupling. The sandwiched structures have reduced magnetic moment as compared to their overlayer counterparts. The MnMn, MnFe, and MnCo sandwiches have highly reduced magnetic moment as compared to their overlayer counterparts.

The full potential linearized augmented plane wave method within the framework of density functional theory (DFT) is employed to investigate the structural, magnetic, electronic and optical properties of Ti-doped ZnTe and CdTe in the zinc blende phase. In this approach the local spin density approximation (LSDA) is used for the exchange-correlation (XC) potential. Results are provided for the lattice constant, bulk modulus, pressure derivative, magnetic moment, band structure, density of states and refractive indices. Our results are compared with other theoretical works and good agreement is shown.

Encapsulation of small clusters in fullerene cages provides a stable environment for their application in nanoscale functional devices. In this paper, first principles study of Ruthenium as an endohedral dopant in buckminsterfullerene has been carried out using density functional theory. Ruthenium atom has three stable dopant sites inside C₆₀, with three possible values of magnetic moment (4, 2 and 0 μB). The doping position of Ru atom can be seen to have an effect on HOMO–LUMO gap, formation energy, binding energy and magnetic moment of the fullerene cage. The interaction between Ru and C atoms in different conformations can be explained in terms of Mulliken analysis and density of states analysis. It is also possible to encapsulate more than one Ru atoms in the C₆₀ cage (Ru_n@C₆₀, n = 2–6); encapsulation up to six atoms has been analyzed, after which the process is energetically unfavorable. The geometry of the lowest energy structures, compared to the isolated Ru_n clusters, is found to change as a result of encapsulation (e.g., in Ru₃@C₆₀ and Ru₅@C₆₀). A reduction in magnetic moment of Ru clusters inside fullerene cage as compared to isolated clusters also occurs due to hybridization and confinement effects. The varied magnetic moments of Ru-encapsulated C₆₀ molecules reveal its applications in molecular magnetic devices and quantum peapods.

The electronic, thermoelectric, optical, and magnetic properties of the samarium aluminate (SmAlO₃) compound is studied using the spin-polarized full-potential linearized augmented plane wave (FP-LAPW) method based on the density functional theory (DFT). The exchange and correlation potential is treated with the generalized gradient approximation (GGA) and the Coulomb repulsion ($U=0.51$ Ry) has been calculated theoretically and was used for the GGA$+U$ based approximated electronic structures. Additionally, the modified Becke–Johnson (mBJ) potential was also utilized along with the GGA$+U$ approach for the calculation of the band gap. On the other hand, the optical properties were analyzed with the mBJ$+U$ results and the thermoelectric properties were explained on the basis of the electronic structures and density of states (DOS) with a thermoelectric efficiency of 0.66 at 300 K. The minimum reflectivity at 1.13 eV (which was equal to 1.097 $\mu$m) was found to be in agreement with the experimental results. Further refinements in the electronic structures were obtained by adding the spin–orbit coupling (SOC) interactions to the GGA$+U$ approach, which was then combined with the mBJ approximations. Hence, a conclusion using the combined mBJ$+U+$SOC study indicates that the SmAlO₃ compound is a potential candidate for both thermoelectric as well as magnetic devices.

The adsorption geometries of CH${}_x$ species (x = 0, 1, 2, 3 and 4) on the metal embedded graphene (M–graphene) substrates and the change in electronic structure and magnetic property of systems are analyzed using the first-principles calculations. The calculated results show that the doped metal atoms can provide transferred electrons to neighboring carbon atoms at defective site and thus exhibit positive charges, as well as turning the adsorption sensing of M–graphene for detecting CH${}_x$ species. Compared with the adsorbed CH₃, the adsorption of C, CH and CH₂ species exhibit more stability ($>$3.0 eV) on M–graphene. Besides, more stable C atom on M–graphene can effectively turn the magnetic property of systems as compared with other species. This result provides a useful reference for fabricating the functional metal–graphene complex as gas sensors and catalytic materials.

First principles calculations have been accomplished for structural, electronic, magnetic and mechanical properties of half Heusler (HH) LiYZ ($\mathrm{\text{Y}}=\mathrm{\text{Ru}}$, Rh and $\mathrm{\text{Z}}=\mathrm{\text{As}}$, Se, Te, Sb) alloys using the density functional theory (DFT) within full potential-linearized augmented plane wave (FP-LAPW) method. To calculate the physical properties, Perdew–Burke–Ernzerhof (PBE) potential and generalized gradient approximation (GGA) are employed. The calculations are accomplished for three phases to obtain the most stable phase. The results of these calculations revealed that Type-III is the most stable of LiRhSe and LiRhSb, Type-I of LiRhAs, LiRhTe, LiRuAs, LiRuSb, LiRuSe and LiRuTe alloys. The structural optimization is obtained by plotting the graphs between minimum volume and the lowest energy of all considered alloys. The results of electronic properties including density of states (DOS) and band structures are also presented. The obtained total magnetic moment (MM) is negative for LiRhSb, LiRuSb, LiRhTe, LiRuTe, while it is positive for LiRhSe, LiRuSe, LiRhAs, LiRuAs Heusler alloys (HAs). To determine the mechanical stability, several parameters such as Poisson’s ratio, Pugh’s ratio, Lame’s coefficient, anisotropy factor, Kleinman parameter, Young’s modulus, Bulk modulus and Cauchy pressure are calculated and discussed in detail.

The orbital magnetic moments induced by a constant magnetic field in a two-dimensional (2D) and three-dimensional (3D) electron gas are calculated on the same footing independent of the conventional method based on statistical thermodynamics. The dependence of the moment on a common size parameter — defined as the cubic root of the volume occupied by one electron in a 3D gas — is found to be a similar monotonic function for both kinds of electron gas. This monotonic dependence is compared with the oscillating function of the size parameter obtained for the magnetic moment calculated in the case of a 2D slice of the tightly-bound s-electron states in a simple-cubic, or body-centred cubic, lattice.