118453673
Emittance growth scaling laws for crossing systematic space-charge driven sixth-order resonances and random octupole driven fourth-order resonances in FFAGs
120908048
Comment on “Quasiperiodic spin-orbit motion and spin tunes in storage rings”
124338422
FIRST OBSERVATION OF A SNAKE DEPOLARIZING RESONANCE
Using a 104MeV stored polarized proton beam and a full Siberian snake, we recently found evidence for a so-called {open_quotes}snake{close_quotes} depolarizing resonance. A full Siberian snake forces the spin tune {nu}{sub s} to be a half integer. Thus, if the vertical betatron tune {nu}{sub y} is set near a quarter integer, then the {nu}{sub s}=n{plus_minus}2{nu}{sub y} second-order snake resonance can depolarize the beam. Indeed, with a full Siberian snake, we found a deep depolarization dip when {nu}{sub y} was equal to 4.756; moreover, when {nu}{sub y} was changed to 4.781, the deep dip disappeared and the polarization was preserved. {copyright} {ital 1997} {ital The American Physical Society}
120417645
Snakes and spin rotators for high energy accelerators
Abstract A modification to the continuous family of snake and spin rotators, discovered by Steffen, is discussed. A compact snake configuration is found to have the advantages of requiring a smaller total integrated dipole magnet strength and a smaller transverse displacement for circulating particles. A split snake configuration has the advantage of allowing an entire experimental insertion region to be located between the two halves of the snake. Such configurations could serve as both a snake and a 90° spin rotator for experiments requiring different helicity states. General properties of these snake configurations are discussed.
117036088
Comparison of multipole expansion and exact form of the eddy current field of the AGS Booster
Studies are made on magnetic field representation using a multipole expansion as well as the exact form to calculate the magnetic field produced by eddy currents in the vacuum chamber of the AGS Booster as well as the field produced by three turn correction coils attached to the top and bottom of the vacuum chamber. The multiple representation of the chamber field does not converge to the next field when X > 30mm and limits the particle motion. When the exact form of the chamber field is used, initial amplitudes in the horizontal plane (measured at QF) can be nearly as large as the chamber half aperture. Use of three turn correction coils to compensate the eddy current fields seems to reduce rather than increase the acceptance. 6 figs., 3 tabs.
96454816
Design and fabrication of a multi-purpose Panofsky magnet
A fast, flexible magnet system, consisting of a Panofsky style ferrite picture-frame magnet and pulsed power supply, has been developed. Magnet specifications are: 8 cm /spl times/8 cm aperture, 23 cm length, 500 A pulsed/l60 A DC, and 1 /spl mu/s risetime. Designed for general accelerator physics studies, the magnet may be quickly converted from dipole to quadrupole or sextupole and higher multipole configurations by easily changing winding end terminations. In the quadrupole configuration a field gradient of 0.5 T/m is achieved at 500 A. This magnet has become an important tool for nonlinear beam dynamics experiments at the IUCF Cooler Ring.<<ETX>>
119519436
A dual gravity study of the (2+1)D compact U(1) gauge theory coupled with strongly interacting matter fields
Abstract We consider the D2-brane probe action in the gravity background dual to N coincident D p -branes by treating the separation between the D2- and D p -branes as a non-dynamical parameter for p = 2 , 4 , 6 . The gauge coupling, the core size of a non-BPS instanton and the mass gap of the compact U ( 1 ) gauge theory in the D2-brane are determined as a function of the separation in the type IIA gravity region. The results are interpreted in terms of the ( 2 + 1 ) D U ( 1 ) gauge theory coupled with the matter fields which are also strongly coupled with the ( p + 1 ) D SU ( N ) gauge field. It is shown that strong coupling of the matter fields to the SU ( N ) gauge field can drastically modify their screening of the U ( 1 ) gauge field. The non-perturbative dependence of the U ( 1 ) gauge coupling on the energy scale is obtained.
3165699
Growth index in an accelerating universe
We obtain the exact analytic form of growth index ($f = \Omega_{m}(a)^{\gamma}$) at present epoch in a flat universe for the general value of constant equation of state of dark energy $\omega_{de}$. For the cosmological constant ($\omega_{de} = -1$) we obtain $\gamma = 0.5547$ which is very close to the well known value 6/11. However, if $\omega_{de} = -0.9$, then $\gamma$ gives rise to 0.6405. This result is quite different from that of some other literatures. This discrepancy happens because the numerical solution includes not only the growing mode solution but also the decaying one in some literatures. Thus, the numerical estimation of $\delta$ is over estimated in some references. $\Omega_{m}^{0}$ dependence of $\gamma$ is fairly small for the viable range of the current matter energy density $0.2 \leq \Omega_{m}^{0} \leq 0.3$. (0.6% and 3% changes in $\gamma$ for $\omega_{de}$ equal to -1 and -0.9, respectively.) The difference of peculiar velocity values from the different choices of $\gamma$ is about 11% for $\Omega_{m}^{0} = 0.3$. This simple but accurate formula which covers a large class of dark energy models will provide a practical tool for galaxy redshift survey to measure the matter density and the peculiar velocity.
118846082
Perturbative non-Fermi liquids from dimensional regularization
We devise a dimensional regularization scheme for quantum field theories with Fermi surface to study scaling behaviour of non-Fermi liquid states in a controlled approximation. Starting from a Fermi surface in two space dimensions, the co-dimension of Fermi surface is extended to a general value while the dimension of Fermi surface is fixed. When Fermi surface is coupled with a critical boson centered at zero momentum, the interaction becomes marginal at a critical space dimension d_c=5/2. A deviation from the critical dimension is used as a small parameter for a systematic expansion. We apply this method to the theory where two patches of Fermi surface is coupled with a critical boson, and show that the Ising-nematic critical point is described by a stable non-Fermi liquid state slightly below the critical dimension. Critical exponents are computed upto the two-loop order.
118495217
Evidence for departure from \Lambda CDM with LSS
We investigate the growth index parameter \gamma and the time variation of the gravitational constant G_{eff} by using the currently available growth function f(z) data at different redshifts, with and without scaling to the fiducial \Lambda CDM model. We inquire the four different models of \gamma including a constant \gamma. From a \chi^2 minimization, we constrain the parameter spaces of models and show that \Lambda CDM model is excluded by 1-\sigma level from current f(z) data. G_{eff} is different from the Newton's gravitational constant G_{N} in modified gravity theories and interestingly, the current data shows that G_{eff} \neq G_{N} at z \gtrsim 0.2 \sim 0.3 at 3-\sigma level. From these, we conclude that Einstein's General Relativity with \Lambda CDM is ruled out by 99% confidence level from large scale structure observations.
118595202
Lagrangian perturbation theory: Third-order solution for general dark energy models
We investigate the Lagrangian perturbation theory of a general dark energy models with a constant equation of state, \omega, and derive the fitting form of the fastest growing mode solutions up to the third order. These fitting forms are less than few % errors compared to the numerical calculation. We also correct the solutions of Einstein-de Sitter and the open universe with the proper initial conditions and the correct consideration for the growing mode solutions in order to compare with the general dark energy models. Even though these fitting forms are limited to the constant equation of state models, one can apply these to the time-varying \omega by interpolating between models with the constant \omega. These fitting forms can be used for the correct prediction for the two point correlation function and can give the proper predictions for the different dark energy models.