1357101
Pulsar magnetospheres: a general relativistic treatment
A fully general relativistic description of pulsar magnetospheres is provided. To be more specific, a study of pulsar magnetospheres is performed in the context of general relativistic magnetohydrodynamics (MHD) employing the so-called Grad–Shafranov approach. Not surprisingly, the resulting Grad–Shafranov equations and all the other related general relativistic MHD equations turn out to take essentially the same structures as those for a (rotating) black hole magnetosphere. Other different natures between the two cases including the structure of singular surfaces of MHD flows in each magnetosphere are essentially encoded in the different space–time (metric) contents. In this way, pulsar and black hole magnetospheres can be described in a unified fashion. Particularly, the direction of poloidal currents circulating in the neutron star magnetosphere turns out to be the same as that of currents circulating in a black hole magnetosphere, which in turn leads to pulsar and black hole spin-down via ‘magnetic braking’.
5695541
Nonvanishing magnetic flux through the slightly charged Kerr black hole
In association with the Blanford-Znajek mechanism for rotational energy extraction from Kerr black holes, it is of some interest to explore how much of magnetic flux can actually penetrate the horizon at least in idealized situations. For completely uncharged Kerr hole case, it has been known for some time that the magnetic flux gets entirely expelled when the hole is maximally-rotating. In the mean time, it is known that when the rotating hole is immersed in an originally uniform magnetic field surrounded by an ionized interstellar medium (plasma), which is a more realistic situation, the hole accretes certain amount of electric charge. In the present work, it is demonstrated that as a result of this accretion charge small enough not to disturb the geometry, the magnetic flux through this slightly charged Kerr hole depends not only on the hole's angular momentum but on the hole's charge as well such that it never vanishes for any value of the hole's angular momentum.
118626590
Instanton solutions mediating tunneling between the degenerate vacua in curved space
We investigate the instanton solution between the degenerate vacua in curved space. We show that there exist $O(4)$-symmetric solutions not only in de Sitter but also in both flat and anti\char21{}de Sitter space. The geometry of the new type of solutions is finite and preserves the ${Z}_{2}$ symmetry. The nontrivial solution corresponding to the tunneling is possible only if gravity is taken into account. The numerical solutions as well as the analytic computations using the thin-wall approximation are presented. We expect that these solutions do not have any negative mode as in the instanton solution.
2929156
Relativistic Electrodynamics of Spinning Compact Objects
A theoretical study of some electrodynamic features of a region close to a slowly-rotating magnetized relativistic star is performed. To be a little more specific, based on the solution-generating method given by Wald, the magnetic fields around both uncharged and (slightly) charged relativistic stars have been obtained. Particularly for a charged relativistic star, again following the argument by Wald, the star was shown to gradually accrete charge until it reached an equilibrium value Q = 2B0J . This value of the equilibrium charge seems to be generic as a rotating black hole is known to accrete exactly the same amount. Although these results are equally relevant to all species of slowly-rotating relativistic stars, we particularly have the rotating neutron star in mind. As such, it would be of some interest to attempt to make contact with a real pulsar case. Thus, we discuss how many of the theoretical results obtained in the present work can be carried over to a realistic, general relativistic description of a pulsar’s magnetosphere.
16162020
Boson Stars with Self-Interacting Quantum Scalar Fields
The Klein-Gordon-Einstein equations of classical real scalar fields have time-dependent solutions (periodic in time). We show that quantum real scalar fields can form non-oscillating (static) solitonic objects, which are quite similar to the solutions describing boson stars formed with classical and quantum complex scalar fields (the latter will be studied in this paper). We numerically analyze the difference between them concerning the mass of boson stars. On the other hand, we suggest an interesting test (a viable process that the boson star may undergo in the early universe) for the formation of boson stars. That is, it is questioned that after a second-order phase transition (a simple toy model will be considered here), what is the fate of the boson star composed of quantum real scalar field.
118417575
Cosmic Background Anisotropy due to Neutrino Oscillations Revisited
This paper has been withdrawn by the author due to a crucial error in several equations.
17888703
Resonant Flavor Oscillations in Electroweak Baryogenesis
Electroweak baryogenesis (EWBG) in extensions of the Standard Model will be tested quantitatively in upcoming nuclear and particle physics experiments, but only to the extent that theoretical computations are robust. Currently there exist orders-of-magnitude discrepancies between treatments of charge transport dynamics during EWBG performed by different groups, each relying on different sets of approximations. In this work, we introduce a consistent power counting scheme (in ratios of length scales) for treating systematically the dynamics of EWBG: CP-asymmetric flavor oscillations, collisions, and diffusion. Within the context of a simplified model of EWBG, we derive the relevant Boltzmann equations using non-equilibrium field theory, and solve them exactly without ansatz for the functional form of the density matrices. We demonstrate the existence of a resonant enhancement in charge production when the flavor oscillation length is comparable to the wall thickness. We compare our results with the existing treatment of EWBG by Konstandin, Prokopec, Schmidt, and Seco (KPSS) who previously identified the importance of flavor oscillations in EWBG. We conclude: (i) the power counting of KPSS breaks down in the resonant regime, and (ii) this leads to substantial underestimation of the charge generated in the unbroken phase, and potentially of the final baryon asymmetry.
118867883
Enhanced nonperturbative effects in Z decays to hadrons
We use soft collinear effective field theory (SCET) to study nonperturbative strong interaction effects in Z decays to hadronic final states that are enhanced in corners of phase space. These occur, for example, in the jet energy distribution for two jet events near E_J=M_Z/2, the thrust distribution near unity and the jet invariant mass distribution near zero. The extent to which such nonperturbative effects for different observables are related is discussed.
118742958
Universality of Nonperturbative Effects in Event Shapes
Nonperturbative effects in event shape distributions can be characterized by shape functions derived in the eikonal approximation or, equivalently, from soft-collinear effective theory. The use of energy flow operators and the boost invariance of the Wilson lines of soft gluons in the shape functions leads to a proof of universality for power corrections to the mean values of event shapes, without invoking the single gluon approximation.
119996421
Factorized, Resummed and Gapped Angularity Distributions in SCET
Angularities τa are a class of event shapes varying in their sensitivity to the substructure of jets in the final state, controlled by a continuous parameter a. Using the framework of soft‐collinear effective theory (SCET), we factorize and calculate e+e− angularity distributions for all a<1, including perturbative resummation to next‐to‐leading logarithmic accuracy and the incorporation of a universal model for the nonperturbative soft function.
119244769
Solutions in IR Modified Horava-Lifshitz Gravity
In order to allow the asymptotically flat, we consider Ho\v{r}ava-Lifshitz gravity theory with a soft violation of the detailed balance condition and obtain various solutions. In particular, we find that such theory coupled to a global monopole leads to a solution representing a space with deficit solid angle, which is well matched with genuine feature of GR.