A large class of $\Lambda < 0$ cosmologies have big-bang / big crunch spacetimes with time-symmetric backgrounds and asymptotically AdS Euclidean continuations suggesting a possible holographic realization. We argue that these models generically time-dependent scalar fields, can lead to realistic at the level homogeneous background geometry, an accelerating phase prior turnaround crunch. first ...

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In this paper, we have simulated the excitation of wake fields in the interaction of an intensive laser pulses having Half-Sine and Gaussian time envelopes with a fully ionized cold plasma using particle in cell (PIC) method. We investigated the dependency of wake filed amplitude to different laser and plasma parameters such as laser wavelength, pulse duration and electron number density. In ad...

Alignment of the accelerating structures is essential for emittance preservation in long linear accelerators such as the Compact Linear Collider (CLIC). The prototype structures for CLIC have four radial waveguides connected to each cell for damping wakefields and this four-fold symmetry is responsible for an octupole component of the radio-frequency fields, phase-shifted 90 degrees with respec...

Abstract. A 200MHz single-cell superconducting Nb-Cu cavity has been fabricated and tested at 4.2 K and at 2.5 K. The low field Q0 reached 1 5 1010 at 4.2 K. The accelerating gradient (Eacc) reached 11 MV/m at a Q0 of 6 108. Two multipacting barriers show up at Eacc = 3 and 1 MV/m. Helium processing is effective in reducing field emission and improving accelerating gradients. The Q-drop is obse...

Backscattered electron (BSE) imaging is most commonly performed by applying accelerating voltages of 10kV and above to the specimen. For imaging of surface detail, the application of a lower accelerating voltage results in less beam penetration, spread and overall specimen damage. A field emission scanning electron microscope (FESEM) operated with high emission current (50μA) was used to increa...

Due to some beam dynamic requirement, accelerating cavities for TESLA injector linacs should be embedded into solenoid magnetic field and TESLA superconducting cavities can not be applied. Consideration shows the Cut Disk Structure (CDS) as a good option for TESLA Normal Conducting (NC) accelerating cavities. The structure cells shape has been optimised at operating frequency 1300 MHz for diffe...

A 324-MHz, 3.115-m long, four-vane-type, radio-frequency quadrupole (RFQ) linac, which will be used as the most upstream accelerating cavity of the KEK/JAERI Joint Project for high-intensity proton accelerator facility, is under development at KEK. It was designed to accelerate a 30-mA H beam from 50 keV to 3 MeV with a 3% duty factor. The accelerating field of the RFQ cavity are stabilized aga...

In this paper, we investigate the dynamics and the evolution of the scale factor of a probe Dpbrane which move in the background of source Dp-branes. Action of the probe brane is described by the Born-Infeld action and the interaction with the background R-R field. When the probe brane moves away from the source branes, it expands by power law, whose index depends on the dimension of the brane....

We show that the phase transition from the decelerating universe to the accelerating universe, which is of relevance to the cosmological coincidence problem, is possible in the semiclassically quantized two-dimensional dilaton gravity by taking into account the noncommutative field variables during the finite time. Initially, the quantum-mechanically induced positive energy from the noncommutat...