119797547
New Agegraphic Dark Energy model in chameleon Brans-Dicke cosmology for different forms of the scale factor
In this work, we study the New Agegraphic Dark Energy (NADE) model (which contains the conformal time η as infrared cut-off) in the framework of Brans-Dicke cosmology with chameleon scalar field which is non-minimally coupled to the matter field. Considering interacting Dark Energy and Dark Matter (DM), we calculate some relevant cosmological parameters, i.e. the equation of state (EoS) parameter, the deceleration parameter q and the evolution of the energy density parameter $\varOmega_{D}'$ for different forms of scale factors, i.e. the power-law, the emergent, the intermediate and the logamediate ones, which leads to different expressions of η.
119244873
Reciprocal NUT spacetimes
In this paper, we study the Ehlers' transformation (sometimes called gravitational duality rotation) for reciprocal static metrics. First, we introduce the concept of reciprocal metric. We prove a theorem which shows how we can construct a certain new static solution of Einstein field equations using a seed metric. Later, we investigate the family of stationary spacetimes of such reciprocal metrics. The key here is a theorem from Ehlers', which relates any static vacuum solution to a unique stationary metric. The stationary metric has a magnetic charge. The spacetime represents Newman-Unti-Tamburino (NUT) solutions. Since any stationary spacetime can be decomposed into a 1 + 3 time-space decomposition, Einstein field equations for any stationary spacetime can be written in the form of Maxwell's equations for gravitoelectromagnetic fields. Further, we show that this set of equations is invariant under reciprocal transformations. An additional point is that the NUT charge changes the sign. As an instructive example, by starting from the reciprocal Schwarzschild as a spherically symmetric solution and reciprocal Morgan–Morgan disk model as seed metrics we find their corresponding stationary spacetimes. Starting from any static seed metric, performing the reciprocal transformation and by applying an additional Ehlers' transformation we obtain a family of NUT spaces with negative NUT factor (reciprocal NUT factors).
119954902
Study of Thermodynamic Quantities in Horava-Lifshitz and f(R) gravity Theories
The present paper reports studies on thermodynamic quantities like temperature of the universe, heat capacity and squared speed of sound in f(R) and Horava-Lifshitz gravity theories. Considering the universe to be filled with dark matter and dark energy we have shown that in all cases the equation of state behaves like quintessence. The thermodynamic quantities have been studied graphically by plotting them against redshift z.
119187323
Behaviour of interacting Ricci dark energy in logarithmic f(T) gravity
In the present work we have considered a modified gravity dubbed as "logarithmic $f(T)$ gravity" and investigated the behavior of Ricci dark energy interacting with pressureless dark matter. We have chosen the interaction term in the form $Q\propto H\delta\rho_{m}$ and investigated the behavior of the Hubble parameter $H$ as a function of the redshift $z$. For this reconstructed $H$ we have investigated the behavior of the density of the Ricci dark energy $\rho_{RDE}$ and density contribution due to torsion $\rho_{T}$. All of the said cosmological parameters are seen to have increasing behavior from higher to lower redshifts for all values of $c^{2}$ pertaining to the Ricci dark energy. Subsequently, we observed the equation of state parameter $w_{RDE}$ in this situation. The equation of state parameter is found to behave like phantom for all choices of $c^{2}$ in the Ricci dark energy.
122658195
A study on modified holographic Ricci dark energy in modified $f(R)$ Horava-Lifshitz gravity
This paper reports a study on modified holographic Ricci dark energy in modified f(R) Hořava–Lifshitz gravity with a power-law form of the scale factor a. The modified Ricci scalar in the said gravity model is denoted R˜ and, accordingly, the modified gravity has the functional form f(R˜) . The analytical solution for the reconstructed f(R˜) has been obtained and it satisfies a sufficient condition for a realistic model. The effective equation of state parameter, ωeff, has been observed to have a quintessence-like behavior. Statefinder trajectories have indicated the attainment of the ΛCDM phase of the universe for the reconstructed f(R˜) .
123730387
Theoretical constraints on kinetic k-essence dark energy model in El-Nabulsi fractional action cosmology
In this work, we considered an effective scalar field theory described by a Lagrangian with a noncanonical kinetic term, which leads to accelerated expansion in the present Universe and is known as k-essence in the framework of the fractional action cosmology recently introduced by El-Nabulsi. We have chosen a particular ansatz for the scale factor and the scalar field, in which both are described as a power-law of the time, t. We have studied the behavior of some cosmological quantities in other models to obtain some useful information about the model considered. We observed that the equation of state parameter, w, has decreasing behavior and it never crosses the phantom divide line (i.e., w = –1). Studying the statefinder pair {r, s} and {w, w′}, we observed that the model considered is able to obtain the ΛCDM phase of the Universe.
111018506
THE CEBAF ENERGY RECOVERY EXPERIMENT: UPDATE AND FUTURE PLANS ∗
A successful GeV scale energy recovery demonstration with a high ratio of peak-to-injection energies (50:1) was carried out on the CEBAF (Continuous Electron Beam Accelerator Facility) recirculating superconducting linear accelerator in the spring of 2003. To gain a quantitative understanding of the beam behavior through the machine, data was taken to characterize the 6D phase space during the CEBAF-ER (CEBAF with Energy Recovery) experimental run. The transverse emittance of the accelerating and energy recovered beams was measured in several locations to ascertain the beam quality preservation during energy recovery. Measurements also included the RF system’s response to the energy recovery process and transverse beam profile of the energy recovered beam. One of the salient conclusions from the experiment is that the energy recovery process does not contribute significantly to the emittance degradation. The current status of the data analysis will be presented as well as plans for a GeV scale energy recovery experimental run with current doubling.
117855388
Summary of Working Group 1 Beam Physics at High Energy Densities
The topics explored in the Working Group 1 at the Advanced Accelerator Concepts Workshop in Baltimore, Maryland (July 5–11, 1998) were concerned with Beam Physics at High Energy Densities. Particle beams of high phase space density and the associated environment of high energy density electromagnetic radiation—both appear at various stages of existing and envisioned colliders. Accordingly, in addition to general discussions on nonlinear Compton scattering, phase-space cooling, coherent electromagnetic emissions and plasma wakefield accelerations schemes, there were focussed discussions and presentations on two major collider frontiers of the day: (a) the severe electromagnetic and hadronic background environment at the IP of high energy multiple-TeV electron-positron-gamma colliders: and (b) muon beams for high energy muon colliders.
109453297
The Cockcroft Institute Wakefields Interest Group
The Cockcroft Institute is a newly created international centre for Accelerator 
Science and Technology in the UK. It is a joint venture between the Universities of 
Lancaster, Liverpool and Manchester, and the Science and Technology Facilities 
Council. The Cockcroft Institute has a large expertise base in Wakefields and 
Impedances which is linked through the Cockcroft Institute Wakefields Interest Group. 
Members of this group have experience in wakefields in linear colliders, ring colliders, 
light sources as well as generic fundamental research and focus on a wide range of 
specialist areas. In this article we summarize the work performed in this important field 
of research at the Cockcroft Institute.
55920624
Electron quantum yields from a barium photocathode illuminated with polarized light
Photoemission measurements with a barium photocathode and a nitrogen laser are reported. The cathode is prepared by evaporating barium onto a copper disc. Radiation from a nitrogen laser (337 nm, 10 ns) is polarized and strikes the cathode surface at variable angles. An electron quantum yield as high as 1/spl times/10/sup -3/ is observed. The dependence of the quantum yield on the beam polarization and angle of incidence is investigated. The results indicate that higher quantum yields are achieved when the laser beam is incident at an angle of /spl sim/55/spl deg/ and is polarized perpendicular to the plane of incidence.<<ETX>>
27302633
Advanced Accelerator Technologies - A Snowmass'96 Subgroup Summary
The authors address the collider physics issues, concepts and technologies of (e{sup +}e{sup -}{gamma}) colliders at a cm. energy of 5 TeV and a luminosity of 10{sup 35} cm{sup -2}s{sup -1}.