Spiky strings in de Sitter space

We study semiclassical spiky strings in de Sitter space and the corresponding Regge trajectories, generalizing the analysis in anti-de Sitter space. In particular we demonstrate that each Regge trajectory has a maximum spin due to de Sitter acceleration, similarly to the folded string studied earlier. While this property is useful for the spectrum to satisfy the Higuchi bound, it makes a nontrivial question how to maintain mildness of high-energy string scattering which we are familiar with in flat space and anti-de Sitter space. Our analysis implies that in order to have infinitely many higher spin states, one needs to consider infinitely many Regge trajectories with an increasing folding number.

Structures, electronic and magnetic properties of transition metals-doped Mg9O9 tubular clusters

The structures, electronic and magnetic attributes of the transition metal (TM) doping Mg9O9 tubular clusters have been investigated using the PBE functional. The results display that the ScMg9O9 and NiMg9O9 clusters are more structurally stable than the other TMMg9O9 clusters. An Sc atom replaces the Mg atom at the edge site of the Mg9O9 clusters, which leads to the Mg atom transferring to the top of an adjacent O atom. Ni atom prefers to occupy the bridge site of the Mg–O bond at a side of the Mg9O9 clusters. VMg9O9 and FeMg9O9 display more kinetic activity than the other TMMg9O9 clusters. The TM atoms lost certain electrons except for Co, Cu and Zn. The maximum spin value of the TM atoms for the ground-state TMMg9O9 clusters occurs at Mn.

Bowling Performance Assessed with a Smart Cricket Ball: A Novel Way of Profiling Bowlers

Profiling of spin bowlers is currently based on the assessment of translational velocity and spin rate (angular velocity). If two spin bowlers impart the same spin rate on the ball, but bowler A generates more spin rate than bowler B, then bowler A has a higher chance to be drafted, although bowler B has the potential to achieve the same spin rate, if the losses are minimized (e.g., by optimizing the bowler’s kinematics through training). We used a smart cricket ball for determining the spin rate and torque imparted on the ball at a high sampling frequency. The ratio of peak torque to maximum spin rate times 100 was used for determining the ‘spin bowling potential’. A ratio of greater than 1 has more potential to improve the spin rate. The spin bowling potential ranged from 0.77 to 1.42. Comparatively, the bowling potential in fast bowlers ranged from 1.46 to 1.95.

AGN anisotropic radiative feedback set by black hole spin

ABSTRACT We consider the impact of anisotropic radiation on the active galactic nucleus (AGN) radiative dusty feedback. The radiation pattern originating from the accretion disc is determined by the central black hole (BH) spin. Here we analyse how such BH spin-induced angular dependence affects the dynamics and energetics of the radiation pressure-driven outflows, as well as AGN obscuration and BH accretion. In addition, we explore the effect of a spatially varying dust-to-gas ratio on the outflow propagation. We obtain two distinct trends for high-spin and low-spin objects, providing a direct connection between anisotropic feedback and BH spin. In the case of maximum spin, powerful quasi-spherical outflows can propagate on large scales, at all inclination angles with fairly uniform energetics. In contrast, in the case of zero spin, only weaker bipolar outflows can be driven in the polar directions. As a result, high BH spins can efficiently clear out the obscuring gas from most directions, whereas low BH spins can only remove dusty gas from the polar regions, hence also determining the overall AGN obscuration geometry. Due to such anisotropic feedback, high BH spins can prevent accretion of gas from most directions (except in the equatorial plane), while low BH spins allow inflows to proceed from a wider range of directions. This may have important implications for the BH growth in the early Universe. Anisotropic radiative dusty feedback, ruled by the BH spin, may thus play a major role in shaping AGN evolution over cosmic time.

The Allure of High Total Angular Momentum Levels in Multiply-Excited Ions

In the interaction of fast ions with dense matter, the collision frequency is high enough to facilitate the simultaneous excitation of several electrons. Such multiply-excited few-electron systems have been exploited variously for plasma diagnostics. Beam-foil spectroscopic techniques, benefiting from the inherent time-resolution offered by the geometry of typical experiments, have proven particularly fruitful for the study of emission patterns and level lifetimes of specific multiply-excited levels, especially those of maximum spin and total angular momentum. Typical cases are recalled to illustrate some general principles. Among many others, earlier beam-foil measurements have targeted the core-excited 2p53s3p 4D7/2 – 2p5 3s3d 4F9/2 transition in several Na-like spectra ranging from S VI to Cu XIX. Data on the six intermediate elements missing at that time are now added. The interest in such atomic systems with multiple excitations and high total angular momentum values is discussed with a variety of examples.

Adiabatic state distribution using anti-ferromagnetic spin systems

Transporting quantum information is an important prerequisite for quantum computers. We study how this can be done in Heisenberg-coupled spin networks using adiabatic control over the coupling strengths. We find that qudits can be transferred and entangled pairs can be created between distant sites of bipartite graphs with a certain balance between the maximum spin of both parts, extending previous results that were limited to linear chains. The transfer fidelity in a small star-shaped network is numerically analysed, and possible experimental implementations are discussed.

The maximum spin of Millisecond Pulsar and the gravitational wave

The gravitational wave radiation will release the energy momentum, which will dissipate the rotation of neutron star while in the accretion process. If the deformation of star is known, then we can estimate the maximum spin frequency of pulsar, based on which we can interpret why the spin periods of all millisecond pulsars cannot be less than one millisecond.