The Fate of Dark Energy

By studying the present cosmological data, particularly on CMB, SNeIA and LSS, we find that the future fate of the universe, for simple linear models of the dark energy equation-of-state, can vary between the extremes of (I) a divergence of the scale factor in as little as 7 Gyr; (II) an infinite lifetime of the universe with dark energy dominant for all future time; (III) a disappearing dark energy where the universe asymptotes as $t \to \infty$ to $a(t) \sim t^{2/3}$ {\it i.e.} matter domination. Our dreadful conclusion is that no amount of data from our past light-cone can select between these future scenarios.Comment: 10 pages LaTeX including 4 eps figures. Minor corrections in tex

Candidates for Inflaton in Quiver Gauge Theory

The inflaton necessary to implement the mechanism of inflationary cosmology has natural candidates in quiver gauge theory. We discuss the dimensionless coefficients of quartic couplings and enumerate scalars which are singlet under the low-energy gauge group. The inflaton mass is generally predicted to be in the TeV region, close to 4 TeV for one specific unified model. A quartic inflaton potential, and a mutated hybrid inflation, are discussed. They can give adequate inflation and appropriate fluctuations but different spectral indices.Comment: LaTeX 10 page

Effects of initial state fluctuations in the final state elliptic flow measurements using the NeXSPheRIO model

We present a systematic study of the effects due to initial condition fluctuations in systems formed by heavy-ion collisions using the hydrodynamical simulation code NeXSPheRIO. The study was based on a sample of events generated simulating Au+Au collisions at center of mass energy of 200 GeV per nucleon pair with impact parameter ranging from most central to peripheral collisions. The capability of the NeXSPheRIO code to control and save the initial condition (IC) as well as the final state particles after the 3D hydrodynamical evolution allows for the investigation of the sensitivity of the experimental observables to the characteristics of the early IC. Comparisons of results from simulated events generated using fluctuating initial conditions and smooth initial condition are presented for the experimental observable elliptic flow parameter ($v_2$) as a function of the transverse momentum, $p_t$, and centrality. We compare $v_2$ values estimated using different methods, and how each method responds to effects of fluctuations in the initial condition. Finally, we quantify the flow fluctuations and compare to the fluctuations of the initial eccentricity of the energy density distribution in the transverse plane.Comment: 10 pages, 13 figures, updated version based on PRC referee's comment

Inflaton Decay in Supergravity and Gravitino Problem

We have recently shown that, if the inflaton has a nonzero vacuum expectation value, it generically couples to any matter fields that appear in the superpotential at the tree level, and to any gauge sectors through anomalies in the supergravity. Through these processes, the inflaton decays into the supersymmetry breaking sector, producing many gravitinos. The inflaton also directly decays into a pair of the gravitinos. Taking account of these processes, we derive constraints on both inflation models and supersymmetry breaking scenarios for avoiding overproduction of the gravitinos.Comment: Talk given at PASCOS-07, to appear in the proceedings. 4 page

Probing Variant Axion Models at LHC

We study collider implications of variant axion models which naturally avoid the cosmological domain wall problem. We find that in such models the branching ratio of $h \to \gamma\gamma$ can be enhanced by a factor of 5 up to 30 as compared with the standard model prediction. The $h \to \gamma\gamma$ process is therefore a promising channel to discover a light Higgs boson at the LHC and to probe the Peccei-Quinn charge assignment of the standard model fields from Yukawa interactions.Comment: 16 pages, 4 figure

Gravitational Wave Spectrum Induced by Primordial Scalar Perturbations

We derive the complete spectrum of gravitational waves induced by primordial scalar perturbations ranging over all observable wavelengths. This scalar-induced contribution can be computed directly from the observed scalar perturbations and general relativity and is, in this sense, independent of the cosmological model for generating the perturbations. The spectrum is scale-invariant on small scales, but has an interesting scale-dependence on large and intermediate scales, where scalar-induced gravitational waves do not redshift and are hence enhanced relative to the background density of the Universe. This contribution to the tensor spectrum is significantly different in form from the direct model-dependent primordial tensor spectrum and, although small in magnitude, it dominates the primordial signal for some cosmological models. We confirm our analytical results by direct numerical integration of the equations of motion.Comment: 19 pages, 5 figure

Two-color photoassociation spectroscopy of ytterbium atoms and the precise determinations of s-wave scattering lengths

By performing high-resolution two-color photoassociation spectroscopy, we have successfully determined the binding energies of several of the last bound states of the homonuclear dimers of six different isotopes of ytterbium. These spectroscopic data are in excellent agreement with theoretical calculations based on a simple model potential, which very precisely predicts the s-wave scattering lengths of all 28 pairs of the seven stable isotopes. The s-wave scattering lengths for collision of two atoms of the same isotopic species are 13.33(18) nm for ^{168}Yb, 3.38(11) nm for ^{170}Yb, -0.15(19) nm for ^{171}Yb, -31.7(3.4) nm for ^{172}Yb, 10.55(11) nm for ^{173}Yb, 5.55(8) nm for ^{174}Yb, and -1.28(23) nm for ^{176}Yb. The coefficient of the lead term of the long-range van der Waals potential of the Yb_2 molecule is C_6=1932(30) atomic units $(E_h a_0^6 \approx 9.573\times 10^{-26}$ J nm^6).Comment: 9 pages, 7 figure

Spatially Resolving Substructures within the Massive Envelope around an Intermediate-mass Protostar: MMS 6/OMC-3

With the Submillimeter Array, the brightest (sub)millimeter continuum source in the OMC-2/3 region, MMS 6, has been observed in the 850 um continuum emission with approximately 10 times better angular resolution than previous studies (~0.3"; ~120 AU at Orion). The deconvolved size, the mass, and the column density of MMS 6-main are estimated to be 0.32"x0.29" (132 AUx120 AU), 0.29 Mo, and 2.1x10^{25} cm^{-2}, respectively. The estimated extremely high mean number density, 1.5x10^{10} cm^{-3}, suggests that MMS 6-main is likely optically thick at 850 um. We compare our observational data with three theoretical core models: prestellar core, protostellar core + disk-like structure, and first adiabatic core. These comparisons clearly show that the observational data cannot be modeled as a simple prestellar core with a gas temperature of 20 K. A self-luminous source is necessary to explain the observed flux density in the (sub)millimeter wavelengths. Our recent detection of a very compact and energetic outflow in the CO (3-2) and HCN (4-3) lines, supports the presence of a protostar. We suggest that MMS 6 is one of the first cases of an intermediate mass protostellar core at an extremely young stage. In addition to the MMS 6-main peak, we have also spatially resolved a number of spiky structures and sub-clumps, distributed over the central 1000 AU. The masses of these sub-clumps are estimated to be 0.066-0.073 Mo, which are on the order of brown dwarf masses. Higher angular resolution and higher sensitivity observations with ALMA and EVLA will reveal the origin and nature of these structures such as whether they are originated from fragmentations, spiral arms, or inhomogeneity within the disk-like structures/envelope.Comment: Accepted to Ap

Effect of vascular burden as measured by vascular indexes upon vascular dementia: a matched case-control study

Paul Y Takahashi, Casey R Caldwell, Paul V TargonskiPrimary Care Internal Medicine, Mayo Clinic, Rochester MN, USABackground: Vascular dementia (VaD) is a challenging illness that affects the lives of older adults and caregivers. It is unclear how multiple vascular risk factor exposures (polyvascular disease) affect VaD.Purpose: To determine the relationship between multiple vascular risk exposures, as counted on an index in cases with VaD, compared with healthy age-/gender-matched controls.Methods: This was a matched case-control study of subjects living in Olmsted County, MN with documented VaD. Controls were selected by gender and age within 3 years from those who did not have dementia. The exposures included a total index (eleven exposure factors) added together, along with indexes for cerebrovascular disease (two exposures), cardiovascular disease (four exposures), vascular disease (three exposures), and lifestyle (two exposures). Analysis used matched conditional univariable logistic regression for each index.Results: A total of 1736 potential subjects were identified, and 205 subjects were diagnosed with VaD. There was a significant association of the total score index with an odds ratio of 1.45 (95% confidence interval 1.21–1.74). The cerebrovascular index was also associated with VaD with an odds ratio of 12.18 (95% confidence interval 6.29–23.61). The cardiovascular and vascular indexes were also associated with VaD status. The lifestyle index was not associated with VaD.Conclusion: The cumulative role of multiple vascular risk factors or diseases increased the risk of VaD, as noted by the total vascular index. The lifestyle index did not reveal any significant differences. Further work is required for evaluation of these indexes.Keywords: polyvascular disease, elderly, vascular dementi

Effect of alcohol and tobacco use on vascular dementia: a matched case control study

Paul Y Takahashi, Casey R Caldwell, Paul V TargonskiPrimary Care Internal Medicine, Mayo Clinic, Rochester, MN, USABackground: Vascular dementia is the second most common type of dementia in the United States. The underlying association of tobacco and alcohol with vascular dementia is not completely understood.Purpose: Determine the relationship of tobacco and alcohol use with the development of vascular dementia (VaD).Methods: This was a matched case-control study of subjects living in Olmsted County, MN. Cases of VaD were identified through medical record abstraction using conventionally accepted definitions of VaD, using the National Institute of Neurological Disorders and Stroke and the Association Internationale pour la Recherche et l'Ensignement en Neurosicences (NINDS-AIRENS) criteria and were matched to controls by gender and age within 3 years among persons free of dementia on the index date. Exposure data for alcohol and tobacco use were abstracted by trained nurses, along with demographic, lifestyle, cerebrovascular, cardiovascular, and vascular comorbid disease characteristics. Matched conditional logistic regression for univariate and multivariate evaluation of the association of tobacco and alcohol use with VaD was utilized.Results: Current alcohol exposure was associated with a decreased risk of VaD with an odds ratio of 0.48 (95% confidence interval: 0.31–0.74). This protective effect of alcohol was seen in men, women, and subjects under 80 years of age. Tobacco use was not associated with VaD in univariate and multivariate analysis, and stratified analysis did not reveal any subgroup-specific associations between tobacco use and VaD in the study population.Conclusion: Current alcohol use appears to have protective effects against the development of vascular dementia. The effects are more pronounced in subjects under age 80. This may reflect the direct vascular effects of alcohol on the vascular system or may represent a surrogate for better social or functional status. Previous alcohol use was not protective. Tobacco use was not a risk factor for VaD status, which was possibly an indication of survivorship bias in the cohort.Keywords: vascular dementia, elderly, alcohol, tobacc