16662994
Hawking-Page phase transition of black Dp-branes and R-charged black holes with an IR cutoff
We show that the confinement-deconfinement phase transition of supersymmetric Yang-Mills theories with W supercharges in various dimensions can be realized through the Hawking-Page phase transition between the near horizon geometries of black Dp-branes and BPS Dp-branes by removing a small radius region in the geometry in order to realize a confinement phase, which generalizes Herzog's discussion for the holographic hard-wall AdS/QCD model. Removing a small radius region in the gravitational dual corresponds to introducing an IR cutoff in the dual field theory. We also discuss the Hawking-Page phase transition between thermal AdS(5), AdS(4), AdS(7) spaces and R-charged AdS black holes coming from the spherical reduction of the decoupling limit of rotating D3-, M2-, and M5- branes in type IIB supergravity and 11 dimensional supergravity in grand canonical ensembles, where the IR cutoff also plays a crucial role in the existence of the phase transition.
118488505
Shear Viscosity from AdS Born-Infeld Black Holes
We calculate the shear viscosity in the frame of AdS/CFT correspondence for the field theory with a gravity dual of Einstein-Born-Infeld gravity. We find that the ratio of η/s is still the conjectured universal value 1/4π at least up to the first order of the Born-Infeld parameter 1/b2.
119106319
Shear Viscosity from the Effective Coupling of Gravitons
).Known experiments such as the Quark-Gluon Plasma(QGP) in RHIC alsosatisfy this conjecture. Then more attention has been payed to the study ofthe universality of η/s through holographic method, and the η/s was foundto be still above 1/4π in Ref. 13–20. However, it was later found that theKSS bound can be slightly violated in theories with gravity dual of moregeneral theories of gravity.
15310424
A Lifshitz black hole in four dimensional R(2) gravity
We consider a higher derivative gravity theory in four dimensions with a negative cosmological constant and show that vacuum solutions of both Lifshitz type and Schrodinger type with arbitrary dynamical exponent z exist in this system. Then we find an analytic black hole solution which asymptotes to the vacuum Lifshitz solution with z = 3/2 at a specific value of the coupling constant. We analyze the thermodynamic behavior of this black hole and find that the black hole has zero entropy while non-zero temperature, which is very similar to the case of BTZ black holes in new massive gravity at a specific coupling. In addition, we find that the three dimensional Lifshitz black hole recently found by E. Ayon-Beato et al. has a negative entropy and mass when the Newton constant is taken to be positive.
118458267
Lattice potentials and fermions in holographic non Fermi-liquids: hybridizing local quantum criticality
A bstractWe study lattice effects in strongly coupled systems of fermions at a finite density described by a holographic dual consisting of fermions in Anti-de-Sitter space in the presence of a Reissner-Nordström black hole. The lattice effect is encoded by a periodic modulation of the chemical potential with a wavelength of order of the intrinsic length scales of the system. This corresponds with a highly complicated “band structure” problem in AdS, which we only manage to solve in the weak potential limit. The “domain wall” fermions in AdS encoding for the Fermi surfaces in the boundary field theory diffract as usually against the periodic lattice, giving rise to band gaps. However, the deep infrared of the field theory as encoded by the near horizon AdS2 geometry in the bulk reacts in a surprising way to the weak potential. The hybridization of the fermions bulk dualizes into a linear combination of CFT1 “local quantum critical” propagators in the bulk, characterized by momentum dependent exponents displaced by lattice Umklapp vectors. This has the consequence that the metals showing quasi-Fermi surfaces cannot be localized in band insulators. In the AdS2 metal regime, where the conformal dimension of the fermionic operator is large and no Fermi surfaces are present at low T/μ, the lattice gives rise to a characteristic dependence of the energy scaling as a function of momentum. We predict crossovers from a high energy standard momentum AdS2 scaling to a low energy regime where exponents found associated with momenta “backscattered” to a lower Brillioun zone in the extended zone scheme. We comment on how these findings can be used as a unique fingerprint for the detection of AdS2 like “pseudogap metals” in the laboratory.
112335527
A Linac Simulation Code for Macro-particles Tracking and Steering Algorithm Implementation
In this paper, a linac simulation code written in Fortran90 is presented and several simulation examples are given. This code is optimized to implement linac alignment and steering algorithms, and evaluate the accelerator errors such as RF phase and acceleration gradient, quadrupole and BPM misalignment. It can track a single particle or a bunch of particles through normal linear accelerator elements such as quadrupole, RF cavity, dipole corrector and drift space. One-to-one steering algorithm and a global alignment (steering) algorithm are implemented in this code.
12679676
Preliminary study on two possible bunch compression schemes at NLCTA
In this paper, two possible bunch compression configurations are proposed and evaluated by numerical simulation in the Next Linear Collider Test Accelerator (NLCTA) at SLAC. A bunch compression ratio up to 20 could be achieved under a perfect condition, without consideration for the timing jitter and other error sources. The NLCTA is a test accelerator built at SLAC, which is approximately 42 meters long and composed of X-band acceleration structures. The main aim of building NLCTA is to develop and demonstrate the X-band rf acceleration technologies for the next generation linear collider, with a relatively high acceleration gradient between 50 MV/m and 100 MV/m. The current operation configuration of NLCTA features a thermionic-cathode electron gun at its starting point which generates an electron beam with an energy of 5 MeV. This is followed by a roughly 1.5 meter long X-band acceleration structure which boosts the electron beam energy to 60 MeV. Then there is a four-dipole magnetic chicane which is 6 meters long and provides a first order longitudinal dispersion of R{sub 56} = -73mm. Next the electron beam passes by several matching quadrupoles and can be accelerated further to 120 MeV through another one-meter-long X-band acceleration structure. After that,more » there are three small chicanes downstream, with a total first order longitudinal dispersion of R{sub 56} = -10mm. A sketch of the main components of NLCTA is shown in Figure 1, where the total length of this accelerator is 45 meters. Free Electron Lasers (FELs), proposed by J. Madey and demonstrated for the first time at Stanford University in 1970s [2] [3], use the lasing of relativistic electron beam traveling through a magnetic undulator, which can reach high power and can be widely tunable in wavelength. Linac based FEL source can provide sufficient brightness, and a short X-ray wavelength down to angstrom scale, which promises in supporting wide range of research experiments. In order to have an electron beam lasing coherently in an undulator, one needs a very bright beam in all three dimensions. In other words, one needs an electron beam with very short bunch length (high intensity), very small transverse emittance and very small energy spread. Most FELs currently being operated, commissioned, constructed or proposed are based on RF acceleration in a frequency range from L-band ( 1 GHz) to C-band ( 6 GHz). As RF frequency goes higher, wake fields effects tend to be much stronger and jitter tolerances are tighter. To demonstrate that X-band acceleration structures can be applied in constructing an FEL, one could perform bunch compression experiments at NLCTA as a first step, and investigate tolerances on timing jitter, misalignments etc.. Another important point is to evaluate the transverse emittance growth in this bunch compression process. In the following sections, two possible bunch compression schemes are proposed to be tested at NLCTA. Elegant [4] 3-D simulation is performed to evaluate these two schemes, with wake fields, space charge and coherent synchrotron radiation (CSR) effects included. One million macro particles are adopted in the numerical simulations. The simulation starts with an electron beam of 20 pC at a beam energy of 5 MeV. The initial RMS bunch length is taken as 0.5 ps at such a low bunch charge, and the RMS energy spread is 5 x 10{sup -3}. The normalized transverse emittance is 1 mm.mrad.« less
17071903
Preliminary study on emittance growth in the LHEC recirculating LINAC
In this paper, we estimate the emittance growth in the LHeC recirculating Linac, the lattice design of which is presented in another paper of IPAC10 proceedings. The possible sources for emittance growth included here are: energy spread from RF acceleration in the SRF (superconducting RF) linac together with large chromatic effects from the lattice, and synchrotron radiation (SR) fluctuations in the recirculating arcs. 6-D multi-particle tracking is launched to calculate the emittance from the statistical point of view. The simulation results are also compared with a theoretical estimation.
18102246
Simple Limits on Achieving A Quasi-Linear Magnetic Compression for an FEL Driver
Free electron lasers (FEL) need a very bright electron beam in three dimensions and a high peak charge density. In order to compress an initially longer electron bunch generated from the photoinjector, magnetic bunch compression systems are widely employed. In this paper, first harmonic RF linearization and its associated requirements are reviewed. Meanwhile it is also briefly discussed what is the relation between a proper initial bunch length and main RF frequency, when a harmonic RF linearization is included. Then given a reasonable bunch compression ratio, a proper initial bunch length as a function of the main RF frequency and RF phase is estimated analytically by several approaches, assuming that no harmonic RF section is needed to linearize the energy modulation introduced during main RF acceleration, and at the same time still linearly compress the bunch length. Next the upper limit of the bunch compression ratio in a single stage is evaluated analytically. The analytical relations derived on choosing a proper initial bunch length as a function of main RF frequency are confirmed by numerical simulation. These simple limit provide rough estimations and may be beneficial for choosing bunch compression ratios in different stages of an FEL driver, especially in a first stage bunch compression where there is usually a harmonic RF linearization applied. It may also be useful in evaluating the possibility of low charge operation mode without any harmonic RF linearization, where a shorter initial bunch length can be achieved from the photoinjector.
107741825
Preliminary Analysis on Linac Oscillation Data LI05-19 and Wake Field Energy Loss in FACET Commissioning 2012
In this note, preliminary analysis on linac ocsillation data in FACET linac LI05-09 plus LI11-19 is presented. Several quadrupoles are identified to possibly have different strength, compared with their designed strength in the MAD optics model. The beam energy loss due to longitudinal wake fields in the S-band linac is also analytically calculated, also by LITRACK numerical simulations.