18840537
Predictions of inflation: the slow roll approximation vs. exact results
Inflation predicts the generation of cosmological perturbations. Usually, the power spectra for the scalar and tensor modes are calculated with help of the slow roll approximation. In the case of power law inflation an exact result is available. We compare the predictions for the cosmic microwave background anisotropies from the slow roll approximation with the exact results from power law inflation. We find that the so-called consistency check from the slow roll approximation, $C_2^T/C_2^S \approx -6.93 n_T$, may differ considerably from the exact result.
119240885
Constraints on moduli cosmology from the production of dark matter and baryon isocurvature fluctuations
We set constraints on moduli cosmology from the production of dark matter—radiation and baryon— radiation isocurvature fluctuations through modulus decay, assuming the modulus remains light during inflation. We find that the moduli problem becomes worse at the perturbative level as a significant part of the parameter space m σ (modulus mass)—σ inf (modulus vacuum expectation value at the end of inflation) is constrained by the nonobservation of significant isocurvature fluctuations. We discuss in detail the evolution of the modulus vacuum expectation value and perturbations, in particular, the consequences of Hubble scale corrections to the modulus potential, and the stochastic motion of the modulus during inflation. We show, in particular, that a high modulus mass scale m σ ≳ 100 TeV, which allows the modulus to evade big bang nucleosynthesis constraints is strongly constrained at the perturbative level. We find that generically, solving the moduli problem requires the inflationary scale to be much smaller than 10 13 GeV.
118612073
Generation of gravitational waves during early structure formation between cosmic inflation and reheating
In the pre-reheating era, following cosmic inflation and preceding radiation domination, the energy density may be dominated by an oscillating massive scalar condensate, such as is the case for V = m22/2 chaotic inflation. We have found in a previous paper that during this period, a wide range of sub-Hubble scale perturbations are subject to a preheating instability, leading to the growth of density perturbations ultimately collapsing to form non-linear structures. We compute here the gravitational wave signal due to these structures in the linear limit and present estimates for emission in the non-linear limit due to various effects: the collapse of halos, the tidal interactions, the evaporation during the conversion of the inflaton condensate into radiation and finally the ensuing turbulent cascades. The gravitational wave signal could be rather large and potentially testable by future detectors.
18746371
Non-vacuum initial states for the cosmological perturbations and the back-reaction problem of inflation
In the framework of Inflationary theory, the assumption that the quantum state of the perturbations is a non-vacuum state leads to a difficulty: non-vacuum initial states imply, in general, a large energy density of inflaton field quanta, not of a cosmological term type, that could prevent the inflationary phase. In this short note, we discuss in detail why this is so, keeping an eye on possible non-Gaussian features due to considering generic non-vacuum initial states.
31268700
Quintessence with two energy scales
We study quintessence models using low energy supergravity inspired from string theory. We consider effective supergravity with two scales m_S, the string scale, and m_PL, the Planck scale and show that quintessence naturally arises from a supersymmetry breaking hidden sector. As long as supersymmetry is broken by the $F$-term of a Polonyi-like field coupled to the quintessence field in the K\"ahler potential we find that the Ratra-Peebles potential and its supergravity version are generic predictions. This requires that the string scale decouples from the Planck scale, m_S << m_PL. In the context of supergravity, the potential possesses a minimum induced by the supergravity corrections to the Ratra-Peebles potential at low redshifts. We study the physical consequences of the presence of this minimum.
14965415
Best unbiased estimators for the three point correlators of the cosmic microwave background radiation
Measuring the three-point correlators of the cosmic microwave background (CMB) anisotropies could help to get a handle on the level of non-Gaussianity present in the observational data sets and therefore would strongly constrain models of the early Universe. However, typically, the expected non-Gaussian signal is very small. Therefore, one has to face the problem of extracting it from the noise, in particular from the ``cosmic variance'' noise. For this purpose, one has to construct the best unbiased estimators for the three-point correlators that are needed for concrete detection of non-Gaussian features. In this article, we study this problem for both the CMB third moment and the CMB angular bispectrum. We emphasize that knowledge of the best estimator for the former does not permit one to infer the best estimator for the latter and vice versa. We present the corresponding best unbiased estimators in both cases and compute their corresponding cosmic variances.
37428412
Coupled Operation of the Oak Ridge Isochronous Cyclotron and the 25 MV Tandem
Coupled operation of the 25 MV tandem and the Oak Ridge Isochronous Cyclotron (ORIC) was achieved on January 27, 1981. A beam of 38 MeV 16O2+ was injected into ORIC, stripped to 8+ and accelerated to 324 MeV. Shortly afterwards, the energy was increased to the maximum design value of 25 MeV/amu (400 MeV). A spectrum taken of the scattering of this beam from a thin 208Pb target in the broad range spectrograph exhibited a resolution of 115 keV (FWHM). Performance of the system was in close agreement with that predicted from calculations.
122793815
The 4-MeV Separated-Orbit Cyclotron
The Separated-Orbit Cyclotron Experiment (SOCE) will extend and complement earlier theoretical and experimental studies and will provide a unique facility for the evaluation of an operating SOC system. The six-sector, fourturn accelerator will provide maximum energies of 4 MeV for protons and deuterons and 8 MeV for 3He++ and 4He++ ions. The output energy is variable over a 2:1 range by adjustment of the magnetic field and acceleration of the ions at the appropriate harmonic of the ion frequency. Ions are injected into the SOC at one quarter the final energy. The injection system consists of a duoplasmatron ion source, a 500-kV dc accelerator, and a three-cavity linear accelerator. Proton currents in the 10-to 20-mA range are predicted. The principal characteristics of the accelerator are given in Table I. All of the major components have been fabricated and delivered on site except the injector's linac cavities, which are expected shortly. The photograph in Fig. 1 shows the accelerator as seen from the control area on a mezzanine about 40 feet away. The SOC sector magnets and rf cavities are in the approximate location, with the dc injector components in the background. The tops of the magnet yokes have been temporarily removed to permit completion of pole tip alignment. An rf power amplifier will be mounted on the outer wall of each cavity. One of the PA units can be seen in the background (Fig. 1) on a test stand with a water-cooled dummy load.
118969271
Lattice design of HISTRAP: Heavy Ion Storage Ring for Atomic Physics
HISTRAP, a Heavy-Ion Storage Ring for Atomic Physics, is a proposed 46.8-m-circumference synchrotron-cooling-storage ring optimized to accelerate, cool, decelerate, and store beams of highly charged very-heavy ions at energies appropriate for advanced atomic physics research. This four-fold symmetrical ring has a maximum bending power of 2 Tm. It has achromatic bends and uses quadrupole triplets for focusing.
122110697
The Holifield Heavy Ion Research Facility
The Holifield Heavy Ion Research Facility has been in routine operation since July 1982. Beams have been provided using both the tandem accelerator alone and a coupled mode in which the Oak Ridge Isochronous Cyclotron is used as an energy booster for tandem beams. The coupled mode has proved to be especially effective and has allowed us to provide a wide range of energetic beams for scheduled experiments. In this report we discuss our operational experience and recent development activities.
115293095
TRENDS IN THE UNITED STATES FOR THE ACCELERATION OF HEAVY IONS.