Compact hyperbolic universe and singularities

Recently many people have discussed the possibility that the universe is hyperbolic and was in an inflationary phase in the early stage. Under these assumptions, it is shown that the universe cannot have compact hyperbolic time-slices. Though the universal covering space of the universe has a past Cauchy horizon and can be extended analytically beyond it, the extended region has densely many points which correspond to singularities of the compact universe. The result is essentially attributed to the ergodicity of the geodesic flow on a compact negatively curved manifold. Validity of the result is also discussed in the case of inhomogeneous universe. Relationship with the strong cosmic censorship conjecture is also discussed.Comment: 8 pages with 7 figure

New Constraint on Open Cold-Dark-Matter Models

We calculate the large-angle cross-correlation between the cosmic-microwave-background (CMB) temperature and the x-ray-background (XRB) intensity expected in an open Universe with cold dark matter (CDM) and a nearly scale-invariant spectrum of adiabatic density perturbations. Results are presented as a function of the nonrelativistic-matter density $\Omega_0$ (in units of the critical density) and the x-ray bias $b_x$ (evaluated at a redshift $z\simeq1$ in evolving-bias models) for both an open Universe and a flat cosmological-constant Universe. Recent experimental upper limits to the amplitude of this cross-correlation provide a new constraint to the $\Omega_0$-$b_x$ parameter space that open-CDM models (and the open-inflation models that produce them) must satisfy.Comment: 4 pages, LaTeX. Revised version contains additional figure that clarifies new constraint. (To appear in PRL.

Fall 1956

Greetings from the Club President (page 2) Winter School and Turf Conference Cancelled for 1957 (2) Value of Turf Clippings (3) Dedication--Minor J. Markuson (4) Interrelations between Design, Construction and Maintenance (6) Golf Course Design (6) Relationship of Golf Course Design to Maintenance Costs (9) Influence of Construction upon maintenance (12) Snow Blue - Snow White (14) Post Emergence Control of Crabgrass (15) Third Generation in Greenkeeping (16) Hand Greens Mowers (17) Equipment (18) Pelham Country Club vs New England Thruway (18) Should Junior Memberships be Allowed (19) Meet the Staff (20) Turf Club News (23) Chairman-superintendent Relationship: Quote by Dickinson (24) Letter To Dean Sieling from New England Golf Course Superintendent\u27s Association (24) Associate Members of Stockbridge Turf Management Club (25) Membership Application Form for Turf Management Club (26

Number--conserving model for boson pairing

An independent pair ansatz is developed for the many body wavefunction of dilute Bose systems. The pair correlation is optimized by minimizing the expectation value of the full hamiltonian (rather than the truncated Bogoliubov one) providing a rigorous energy upper bound. In contrast with the Jastrow model, hypernetted chain theory provides closed-form exactly solvable equations for the optimized pair correlation. The model involves both condensate and coherent pairing with number conservation and kinetic energy sum rules satisfied exactly and the compressibility sum rule obeyed at low density. We compute, for bulk boson matter at a given density and zero temperature, (i) the two--body distribution function, (ii) the energy per particle, (iii) the sound velocity, (iv) the chemical potential, (v) the momentum distribution and its condensate fraction and (vi) the pairing function, which quantifies the ODLRO resulting from the structural properties of the two--particle density matrix. The connections with the low--density expansion and Bogoliubov theory are analyzed at different density values, including the density and scattering length regime of interest of trapped-atoms Bose--Einstein condensates. Comparison with the available Diffusion Monte Carlo results is also made.Comment: 21 pages, 12 figure

Open Universes from Finite Radius Bubbles

The interior of a vacuum bubble in de Sitter space may give an open universe with sufficient homogeneity to agree with observations. Here, previous work by Bucher, Goldhaber and Turok is extended to describe a thin bubble wall with nonzero radius and energy difference across the wall. The vacuum modes present before formation of the bubble propagate into the interior of open universe and the power spectrum of the resulting gauge invariant gravitational potential is calculated. It is found to become scale invariant on small scales, with onset at about the same scale as that found in the zero radius case. There is sensitivity to the radius and energy difference at large scales, but it is expected that they cannot be strongly constrained because of cosmic variance. As the prediction of a scale invariant spectrum is robust with respect to variation of these parameters at small scales, it is a generic feature of the contribution of these modes for these thin wall models.Comment: 15 pages, LaTeX and revtex macros, final version to appear in Physical Review D, typos and minor wording change

Can COBE see the shape of the universe?

In recent years, the large angle COBE--DMR data have been used to place constraints on the size and shape of certain topologically compact models of the universe. Here we show that this approach does not work for generic compact models. In particular, we show that compact hyperbolic models do not suffer the same loss of large angle power seen in flat or spherical models. This follows from applying a topological theorem to show that generic hyperbolic three manifolds support long wavelength fluctuations, and by taking into account the dominant role played by the integrated Sachs-Wolfe effect in a hyperbolic universe.Comment: 16 Pages, 5 Figures. Version published in Phys. Rev.

1960

Recent Developments Affecting Golf Course Design (page 1) From the Editor (3) Five Year Results (3) Turf Management Club News (4) Quotes from 1960 Seniors (5) Poa annua - - Friend or Foe (6) The Horticulture Show (7) Cartoons (8) Message from the Winter School President of 1960 (10) The Most Outstanding Turf Senior for 1959 (10) The Value of the Proper Use of Lime (11) Summer Placement (12) A Greenhouse on the Golf Course (13) More Opportunities in the Future for the Aggressive Superintendent at Country Clubs (14) Soil, Sawdust and Turfgrass (15) Picture - Senior Stockbridge Turf majors (16) Picture - Freshman Stockbridge Turf majors (17) Susceptibility of Merion Bluegrass to Stripe Smut (18) Bents in the South (19) Picture - Honorary Members of Turf Management Club (20) Picture - Graduates of Winter School for Turf mangers- 1960 (21) Weather - We are Going to Have Weather, Whether or Not - What Should we Expect by O. Tennebaum & R. E. Lautzenheiser (A-1) The Nature of Winter Injury to Plants by Dr. Johnson Parker (A-1) Turf Problems: You Name it and We\u27ve Had It in \u2759 by Alexander Radko ad T.T. Taylor (A-3) Topdressing Experiences with Greens at Century by James Fulwider (A-5) Poa annua - Fairway Rennovation at winged Foot by Sherwood A. Moore (A-6) Winter Problems at Ekwanaok by Paul O\u27Leary (A-8) Progress Through Drainage by Kayem Ovian (A-10) Winter Injury on Home Lawns by Orlando Capizzi (A-12) The Status of Pre-emergence Chemicals for the Control of Crabgrass by Dr. E. Engel (A-12) Turf Nurseries - Establishment, Maintenance & Utilization by Robert Grant (A-14) Soil Compaction by Dr. R. B. Alderfer (A-16) Water Management Practices on Turf Areas by Dr. J.R. Watson (A-18) Getting to Know Your Members by Owen Griffith (A-23) New Trends in Clubhouse Landscaping by Alfred Boicourt (A-26) General Lawn Management (Alternate Session) Conserving Soil for a good Lawn by Dr. William G. Colby (A-27) Fertilizting and Liming by Dr. Joseph Steckel (A-28) Grasses and Grass Mixtures for New England Lawns by Dr. Robert Schery (A-29) The Care and Maintenance of Establishment Lawns by Dr. John R. Davi

Planck 2015 results. XVIII. Background geometry and topology of the Universe

Maps of cosmic microwave background (CMB) temperature and polarization from the 2015 release of Planck data provide the highestquality full-sky view of the surface of last scattering available to date. This enables us to detect possible departures from a globally isotropic cosmology. We present the first searches using CMB polarization for correlations induced by a possible non-trivial topology with a fundamental domain that intersects, or nearly intersects, the last-scattering surface (at comoving distance χrec), both via a direct scan for matched circular patterns at the intersections and by an optimal likelihood calculation for specific topologies. We specialize to flat spaces with cubic toroidal (T3) and slab (T1) topologies, finding that explicit searches for the latter are sensitive to other topologies with antipodal symmetry. These searches yield no detection of a compact topology with a scale below the diameter of the last-scattering surface. The limits on the radius ℛi of the largest sphere inscribed in the fundamental domain (at log-likelihood ratio Δlnℒ > −5 relative to a simply-connected flat Planck best-fit model) are: ℛi > 0.97 χrec for the T3 cubic torus; and ℛi > 0.56 χrec for the T1 slab. The limit for the T3 cubic torus from the matched-circles search is numerically equivalent, ℛi > 0.97 χrec at 99% confidence level from polarization data alone. We also perform a Bayesian search for an anisotropic global Bianchi VIIh geometry. In the non-physical setting, where the Bianchi cosmology is decoupled from the standard cosmology, Planck temperature data favour the inclusion of a Bianchi component with a Bayes factor of at least 2.3 units of log-evidence. However, the cosmological parameters that generate this pattern are in strong disagreement with those found from CMB anisotropy data alone. Fitting the induced polarization pattern for this model to the Planck data requires an amplitude of −0.10 ± 0.04 compared to the value of + 1 if the model were to be correct. In the physically motivated setting, where the Bianchi parameters are coupled and fitted simultaneously with the standard cosmological parameters, we find no evidence for a Bianchi VIIh cosmology and constrain the vorticity of such models to (ω/H)0 < 7.6 × 10-10 (95% CL)

Search for anisotropic gravitational-wave backgrounds using data from Advanced LIGO and Advanced Virgo's first three observing runs

We report results from searches for anisotropic stochastic gravitational-wave backgrounds using data from the first three observing runs of the Advanced LIGO and Advanced Virgo detectors. For the first time, we include Virgo data in our analysis and run our search with a new efficient pipeline called {\tt PyStoch} on data folded over one sidereal day. We use gravitational-wave radiometry (broadband and narrow band) to produce sky maps of stochastic gravitational-wave backgrounds and to search for gravitational waves from point sources. A spherical harmonic decomposition method is employed to look for gravitational-wave emission from spatially-extended sources. Neither technique found evidence of gravitational-wave signals. Hence we derive 95\% confidence-level upper limit sky maps on the gravitational-wave energy flux from broadband point sources, ranging from $F_{\alpha, \Theta} < {\rm (0.013 - 7.6)} \times 10^{-8} {\rm erg \, cm^{-2} \, s^{-1} \, Hz^{-1}},$ and on the (normalized) gravitational-wave energy density spectrum from extended sources, ranging from $\Omega_{\alpha, \Theta} < {\rm (0.57 - 9.3)} \times 10^{-9} \, {\rm sr^{-1}}$, depending on direction ($\Theta$) and spectral index ($\alpha$). These limits improve upon previous limits by factors of $2.9 - 3.5$. We also set 95\% confidence level upper limits on the frequency-dependent strain amplitudes of quasimonochromatic gravitational waves coming from three interesting targets, Scorpius X-1, SN 1987A and the Galactic Center, with best upper limits range from $h_0 < {\rm (1.7-2.1)} \times 10^{-25},$ a factor of $\geq 2.0$ improvement compared to previous stochastic radiometer searches.Comment: 23 Pages, 9 Figure