نتایج جستجو برای: transition radiation
تعداد نتایج: 495204 فیلتر نتایج به سال:
We show that, unlike the results presented previously in the literature, the transition from an outer Shakura-Sunyaev disk (SSD) to an advectiondominated accretion flow (ADAF) is possible for large values of the viscosity parameter α > 0.5. The transition is triggered by thermal instability of a radiation-pressure-supported SSD. The transition radius is close to the central black hole. We confi...
The standard requirement for the production of baryons at the electroweak phase transition, that the phase transition be first order and the sphaleron bound be satisfied, is predicated on the assumption of a radiation dominated universe at that epoch. One simple alternative-domination by the energy in a kinetic mode of a scalar field which scales as 1/a 6-gives a significantly weakened sphalero...
We discuss some of the cosmological consequences of a late-time ( z 5 lo3) phase transition which produces light domain walls. The observed peculiar velocity field of the Universe and the observed isotropy of the microwave background radiation severely constrain the wall surface density (= a) in such a scenario: Go 5 10-4H~ (Ho is the present value of the Hubble parameter). The most interesting...
We present a new signature by which one could potentially discriminate between a spectrum of gravitational radiation generated by a self-ordering scalar field vs that of inflation, specifically a comparison of the magnitude of a flat spectrum at frequencies probed by future direct detection experiments to the magnitude of a possible polarization signal in the cosmic microwave background radiati...
The Linear Collider presents new challenges for beam instrumentation. Some of the beam dimensions are of the order of a few nm (at the i.p.), and to be able to reach these small sizes, the beams have to be tightly controlled and understood from their very inception onward. A number of different techniques are available in the arsenal of beam size and beam emittance measurements (e.g. transition...
Despite the fact that ionizing radiation (IR) is widely used as a standard treatment for breast cancer, much evidence suggests that IR paradoxically promotes cancer malignancy. However, the molecular mechanisms underlying radiation-induced cancer progression remain obscure. Here, we report that irradiation activates SRC signaling among SRC family kinase proteins, thereby promoting malignant phe...
The linac driven coherent THz radiation source at the SPARC-LAB test facility is able to deliver broadband THz pulses with femtosecond shaping. In addition, high peak power, narrow spectral bandwidth THz radiation can be also generated, taking advantage of advanced electron beam manipulation techniques, able to generate an adjustable train of electron bunches with a sub-picosecond length and wi...
We present a complete relativistic analysis for the scalar radiation emitted by a particle in circular orbit around a Schwarzschild-antide Sitter black hole. If the black hole is large, then the radiation is concentrated in narrow angleshigh multipolar distributioni.e., the radiation is synchrotronic. However, small black holes exhibit a totally different behavior: in the small black hole regim...
The 109.1-nm transition in neutral Cs is the prototype of a class of transitions that originate from doubly excited quasi-metastable quartet levels. In this Letter we describe experiments that use tunable VUV radiation to determine the identity of this transition, to measure its oscillator strength, and to estimate its hyperfine splitting.
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