113405504
He I D3 Observations of the 1984 May 22 M6.3 Solar Flare
The He I D3 line has a unique response to a flare impact on the low solar atmosphere and can be a powerful diagnostic tool for energy transport processes. Using images obtained from the recently digitized films of the Big Bear Solar Observatory, we report D3 observations of the M6.3 flare on 1984 May 22, which occurred in an active region with a circular magnetic polarity inversion line (PIL). The impulsive phase of the flare starts with a main elongated source that darkens in D3, inside of which bright emission kernels appear at the time of the initial small peak in hard X-rays (HXRs). These flare cores subsequently evolve into a sharp emission strand lying within the dark halo; this evolution occurs at the same time as the main peak in HXRs, reversing the overall source contrast from ?5% to 5%. The radiated energy in D3 during the main peak is estimated to be about 1030 erg, which is comparable to that carried by nonthermal electrons above 20?keV. Afterward, the flare proceeds along the circular PIL in the counterclockwise direction to form a dark circular ribbon in D3, which apparently mirrors the bright ribbons in H? and He I 10830 ?. All of these ribbons last for over one hour in the late gradual phase. We suggest that the present event resembles the so-called black-light flare that was proposed based on continuum images, and that D3 darkening and brightening features herein may be due to thermal conduction heating and the direct precipitation of high-energy electrons, respectively.
118706139
MOTIONS OF HARD X-RAY SOURCES DURING AN ASYMMETRIC ERUPTION
Filament eruptions and hard X-ray (HXR) source motions are commonly observed in solar flares, which provide critical information on the coronal magnetic reconnection. This Letter reports an event on 2005 January 15, in which we found an asymmetric filament eruption and a subsequent coronal mass ejection together with complicated motions of HXR sources during the GOES-class X2.6 flare. The HXR sources initially converge to the magnetic polarity inversion line (PIL), and then move in directions either parallel or perpendicular to the PIL depending on the local field configuration. We distinguish the evolution of the HXR source motion in four phases and associate each of them with distinct regions of coronal magnetic fields as reconstructed using a nonlinear force-free field extrapolation. It is found that the magnetic reconnection proceeds along the PIL toward the regions where the overlying field decreases with height more rapidly. It is also found that not only the perpendicular but the parallel motion of the HXR sources correlates well with the HXR light curve. These results are discussed in favor of the torus instability as an important factor in the eruptive process.
15929904
The Spatial Distribution of the Hard X-Ray Spectral Index and the Local Magnetic Reconnection Rate
The rare phenomenon of ribbon-like hard X-ray (HXR) sources up to 100 keV found in the 2005 May 13 M8.0 flare observed with the Reuven Ramaty High Energy Solar Spectroscopic Imager provides detailed information on the spatial distribution of flare HXR emission. In this Letter, we further investigate the characteristics of HXR emission in this event using imaging spectroscopy, from which we obtain spatially resolved HXR spectral maps during the flare impulsive phase. As a result we found, along a flare ribbon, an anticorrelation relationship between the local HXR flux and the local HXR spectral index. We suggest that this can be regarded as a spatial analog of the well-known temporal soft-hard-soft spectral evolution pattern of the integrated HXR flux. We also found an anticorrelation between the HXR spectral index and the local electric field along the ribbon, which suggests electron acceleration by the electric field during flares.
118503556
Causality problem in a holographic-dark-energy model
In the model of holographic dark energy, there is a notorious problem of circular reasoning between the introduction of future event horizon and the accelerating expansion of the universe. We examine the problem after dividing it into two parts, the causality problem of the equation of motion and the circular logic on the use of the future event horizon. We specify and isolate the root of the two problems as a boundary condition from the causal equation of motion, which can be determined from the initial data of the universe. We show that the causality will be kept if we define it based on our recognizability and the circular-logic problem can be reduced to imposing an initial condition. We additionally find that the model constant of the holographic dark energy is close to unity from the present data of the universe.
119508639
INCLUSIVE PRODUCTION OF FOUR CHARM HADRONS AT B-FACTORIES
Measurements by the Belle Collaboration of the exclusive J/ψ + ηc and inclusive $J/\psi + c\bar{c} + X$ productions in e+e- annihilation differ substantially from theoretical predictions based on the nonrelativistic QCD factorization approach. In order to test if such a discrepancy is originated from the large perturbative corrections to the hard-scattering amplitude, we study inclusive production of four charm hadrons in e+e- annihilation at B factories.
15489354
Phenomenology of the radion in the Randall–Sundrum scenario at colliders
Abstract Phenomenology of a radion ( φ ) that stabilizes the modulus in the Randall–Sundrum scenario is considered. The radion couples to the trace of energy momentum tensor of the standard model (SM) with a strength suppressed only by a new scale ( Λ φ ) of an order of the electroweak scale. In particular, the effective coupling of a radion to two gluons is enhanced due to the trace anomaly of QCD. Therefore, its production cross section at hadron colliders could be enhanced, and the dominant decay mode of a relatively light radion is φ → gg , unlike the SM Higgs boson case. We also present constraints on the mass m φ and the new scale Λ φ from the Higgs search limit at LEP and perturbative unitarity bound.
14107601
Cosmological Imprint of the Second Law of Thermodynamics
We study the evolution of the universe in the presence of inflaton, matter, radiation and holographic dark energy. The time evolution of the scale factor is obtained by solving the Friedmann equation of the universe with a good approximation. We present two independent ways which determine the value of the dark energy constant d~1 from the observational data. The two ways are measuring the deceleration parameter and measuring a universal constant depending only on d. The universal constant is given by a dimensionless combination of three scale factors at the equipartition times of radiation–matter, radiation–dark energy and matter–dark energy. We also discuss that the second law of thermodynamics determines the point of time when the dark-energy-dominated era begins in the universe.
118846990
String or brane-like solutions in four-dimensional Einstein gravity in the presence of cosmological constant
We investigate string or branelike solutions for four-dimensional vacuum Einstein equations in the presence of a cosmological constant. For the case of negative cosmological constant, the Banados-Teitelboim-Zanelli black string is the only warped stringlike solution. The general solutions for nonwarped branelike configurations are found and they are characterized by the Arnowitt-Deser-Misner mass density and two tensions. Interestingly, the sum of these tensions is equal to the minus of the mass density. Other than the well-known black string and soliton spacetimes, all the static solutions possess naked singularities. The time-dependent solutions can be regarded as the anti-de Sitter extension of the well-known Kasner solutions. The speciality of those static regular solutions and the implication of singular solutions are also discussed in the context of cylindrical matter collapse. For the case of positive cosmological constant, the Kasner-de Sitter spacetime appears as time-dependent solutions and all static solutions are found to be naked singular.