arXiv subjects

Joel S. Jayson

Publications and source records attributed to Joel S. Jayson.

4 recordsLinked to original sources

arXiv2025

Evaluation of multi-parameter likelihoods through iteration of two-dimensional slices

In this paper we introduce a method for resolving multi-parameter likelihoods by fixing all parameter values, but two. Evaluation of those two variables is followed by iteratively cycling through each of the parameters in turn until convergence. We test the technique on the temperature power spectrum of the lensed cosmic microwave background (CMB). That demonstration is particularly effective since one of the six parameters that define the power spectra, the power spectrum amplitude, $A_{s}$, nears linearity at small deviations, reducing computation to incrementation in one-dimension, rather than over a 2D grid. At each iterative step $A_{s}$ is paired with a different parameter. The iterative process yields parameter values in agreement with those derived by \textit{Planck}, and results are obtained within a few hundred calls for spectra. We further compute parameter values as a function of maximum multipole, $\ell_{\text{max}}$, spanning a range from $\ell_{\text{max}}$=959 to 2500, and uncover bi-modal behavior at the lower end of that range. In the general case, in which neither variable is linear, we identify moderating factors, such as changing both parameters each iterative step, reducing the number of steps per iteration. Markov chain Monte Carlo (MCMC) computation has been the dominant instrument for evaluating multi-parameter functions. For applications with a quasi-linear variable such as, $A_s$, the 2D iterative method is orders of magnitude more efficient than MCMC.

astro-ph.IM↗

arXiv2020

Probing BAO studies with flat $Λ$CDM constraints

One of the algorithms typically used for fitting anisotropic Baryon Acoustic Oscillations (BAO), $α_{\perp}D_{M, \text{fid}}(z)/r_{d, \text{fid}}=D_{M}(z)/r_{d}$, provides an excellent fit as $z\Rightarrow 0$. Yet, at $ z_{\text{drag}} \simeq 1060$, $D_{M, \text{fid}}(1060)/r_{d, \text{fid}}\simeq D_{M}(1060)/r_{d}$. Since $α_{\perp}$ does not change with increasing redshift, we conclude that the algorithms deviate from true solutions with increasing $z$. We investigate that departure through an assumption of a flat $Λ$CDM cosmology. At the relatively low redshifts at which isotropic BAO studies were performed, the divergence is smaller than study uncertainties. However, while the transverse measure, $α_{\perp}$ provides a reliable value in real space, not corrupted by redshift distortion, the isotropic measure, $α$, has a radial component, and is influenced by redshift distortion. That distortion recommends against the inclusion of isotropic studies in cosmological parameter evaluations. At the high redshifts of Ly$α$ forest BAO studies, $z\sim$ 2.35, the deviations of the anisotropic BAO algorithms from the flat $Λ$CDM solutions give rise to markedly deceptive results. We replicate an example, in which those algorithms lead to a value of $Ω_{m}$ which is more than 15 per cent lower than that of the flat $Λ$CDM cosmology computation. The BAO algorithms are inappropriate for the next generation of BAO studies. A flat $Λ$CDM analysis offers an alternative means of assessment.

astro-ph.CO↗

arXiv2016

Application of USNO-B1.0 towards selecting objects with displaced blue and red components

We have conducted a feasibility study to determine the effectiveness of using USNO-B1.0 data to preferentially detect objects with displaced red and blue components. A procedure was developed to search catalogue entries for such objects, which include M dwarfs paired with white dwarfs or with earlier main-sequence stars, and galaxies with asymmetric colour distributions. Residual differences between red and blue and infrared and blue scanned emulsion images define vectors, which, when appropriately aligned and of sufficient length, signal potential candidates. Test sample sets were analysed to evaluate the effective discrimination of the technique. Over 91,000 USNO-B1.0 catalogue entries at points throughout the celestial sphere were then filtered for acceptable combinations of entry observations and magnitudes and the resulting total of about 17,000 entries was winnowed down to a little more than 200 objects of interest. These were screened by visual examination of photo images to a final total of 146 candidates. About one quarter of these candidates coincide with SDSS data. Those constituents fall into two groups, single and paired objects. SDSS identified several galaxies in the first group. Regarding the second group, at least half of its members were tentatively identified as main-sequence pairs, the greater portion being of widely separated spectral types. Two white dwarf--main-sequence pairs were also identified. Most importantly, the vectors formed from USNO-B1.0 residuals were in alignment with corresponding SDSS pair position angles, thereby supporting this work`s central thesis.

astro-ph.IM↗

arXiv2015

The Daniell Cell, Ohm's Law and the Emergence of the International System of Units

Telegraphy originated in the 1830s and 40s and flourished in the following decades, but with a patchwork of electrical standards. Electromotive force was for the most part measured in units of the predominant Daniell cell. Each company had their own resistance standard. In 1862 the British Association for the Advancement of Science formed a committee to address this situation. By 1873 they had given definition to the electromagnetic system of units (emu) and defined the practical units of the ohm as ${10}^9$ emu units of resistance and the volt as ${10}^8$ emu units of electromotive force. These recommendations were ratified and expanded upon in a series of international congresses held between 1881 and 1904. A proposal by Giovanni Giorgi in 1901 took advantage of a coincidence between the conversion of the units of energy in the emu system (the erg) and in the practical system (the joule) in that the same conversion factor existed between the cgs based emu system and a theretofore undefined MKS system. By introducing another unit, X (where X could be any of the practical electrical units), Giorgi demonstrated that a self consistent MKSX system was tenable without the need for multiplying factors. Ultimately the ampere was selected as the fourth unit. It took nearly 60 years, but in 1960 Giorgi's proposal was incorporated as the core of the newly inaugurated International System of Units (SI). This article surveys the physics, physicists and events that contributed to those developments.

physics.hist-ph↗