An Isocurvature Mechanism for Structure Formation

We examine a novel mechanism for structure formation involving initial number density fluctuations between relativistic species, one of which then undergoes a temporary downward variation in its equation of state and generates superhorizon-scale density fluctuations. Isocurvature decaying dark matter models (iDDM) provide concrete examples. This mechanism solves the phenomenological problems of traditional isocurvature models, allowing iDDM models to fit the current CMB and large-scale structure data, while still providing novel behavior. We characterize the decaying dark matter and its decay products as a single component of ``generalized dark matter''. This simplifies calculations in decaying dark matter models and others that utilize this mechanism for structure formation.Comment: 4 pages, 3 figures, submitted to PRD (rapid communications

Nonsymmetric transverse vibrations of truncated conical shells technical report no. 3

Resonant frequencies and associated mode shapes of truncated conical shells over wide range of geometrical and modal parameter

Model-Independent Reionization Observables in the CMB

We represent the reionization history of the universe as a free function in redshift and study the potential for its extraction from CMB polarization spectra. From a principal component analysis, we show that the ionization history information is contained in 5 modes, resembling low-order Fourier modes in redshift space. The amplitude of these modes represent a compact description of the observable properties of reionization in the CMB, easily predicted given a model for the ionization fraction. Measurement of these modes can ultimately constrain the total optical depth, or equivalently the initial amplitude of fluctuations to the 1% level regardless of the true model for reionization.Comment: 4 pages, 5 figures, submitted to PRD (rapid communications

Fluctuations in the Cosmic Microwave Background I: Form Factors and their Calculation in Synchronous Gauge

It is shown that the fluctuation in the temperature of the cosmic microwave background in any direction may be evaluated as an integral involving scalar and dipole form factors, which incorporate all relevant information about acoustic oscillations before the time of last scattering. A companion paper gives asymptotic expressions for the multipole coefficient $C_\ell$ in terms of these form factors. Explicit expressions are given here for the form factors in a simplified hydrodynamic model for the evolution of perturbations.Comment: 35 pages, no figures. Improved treatment of damping, including both Landau and Silk damping; inclusion of late-time effects; several references added; minor changes and corrections made. Accepted for publication in Phys. Rev. D1

Fluctuations of the vacuum energy density of quantum fields in curved spacetime via generalized zeta functions

For quantum fields on a curved spacetime with an Euclidean section, we derive a general expression for the stress energy tensor two-point function in terms of the effective action. The renormalized two-point function is given in terms of the second variation of the Mellin transform of the trace of the heat kernel for the quantum fields. For systems for which a spectral decomposition of the wave opearator is possible, we give an exact expression for this two-point function. Explicit examples of the variance to the mean ratio $\Delta' = (-^2)/(^2)$ of the vacuum energy density $\rho$ of a massless scalar field are computed for the spatial topologies of $R^d\times S^1$ and $S^3$, with results of $\Delta'(R^d\times S^1) =(d+1)(d+2)/2$, and $\Delta'(S^3) = 111$ respectively. The large variance signifies the importance of quantum fluctuations and has important implications for the validity of semiclassical gravity theories at sub-Planckian scales. The method presented here can facilitate the calculation of stress-energy fluctuations for quantum fields useful for the analysis of fluctuation effects and critical phenomena in problems ranging from atom optics and mesoscopic physics to early universe and black hole physics.Comment: Uses revte

Predicting Solid-State Heats of Formation of Newly Synthesized Polynitrogen Materials by Using Quantum Mechanical Calculations

We present density functional theory level predictions and analysis of the basic properties of newly synthesized high-nitrogen compounds together with 3,6-bis(2H-tetrazol-5-yl)-1,2,4,5-tetrazine (BTT) and 3,3′-azobis(6-amino-1,2,4,5-tetrazine) (DAAT), for which experimental data are available. The newly synthesized high-nitrogen compounds are based on tricycle fused 1,2,4-triazine and 1,2,4,5-tetrazine heterocycles. In this work, the molecules BTT and DAAT have been studied in order to validate the theoretical approach and to facilitate further progress developments for the molecules of interest. Molecular structural properties are clarified, and IR spectra predictions are provided to help detection of those compounds in the experiment. The energy content of the molecules in the gas phase is evaluated by calculating standard enthalpies of formation, by using a special selection of isodesmic reaction paths. We also include estimates of the condensed-phase heats of formation and heats of sublimation in the framework of the Politzer approach. The obtained properties are consistent with those new high-nitrogen compounds being a promising set of advanced energetic materials