Papers by Siddharth Satpathy
The bond market is very important to the economy. Compared to equities, bonds have lower liquidit... more The bond market is very important to the economy. Compared to equities, bonds have lower liquidity and transparency; hence, there is less public data available. Adding information from correlated assets with greater liquidity would help increase forecasting accuracy for bond prices. In this work, we construct a pipeline for bond forecasting with factors. We choose factors that are considered to affect bond prices in finance literature, recover the structure of a graphical model, and use the resulting factors for forecasting.
Fano interference in classical oscillators
European Journal of Physics, May 4, 2012
We seek to illustrate Fano interference in a classical coupled oscillator by using classical anal... more We seek to illustrate Fano interference in a classical coupled oscillator by using classical analogues of the atom–laser interaction. We present an analogy between the dressed state picture of coherent atom–laser interaction and a classical coupled oscillator. The Autler–Townes splitting due to the atom–laser interaction is analogous to the splitting of normal-mode frequencies of a coupled oscillator. Using this analogy,
We present measurements of the Baryon Acoustic Oscillation (BAO) scale in redshift-space using th... more We present measurements of the Baryon Acoustic Oscillation (BAO) scale in redshift-space using the clustering of quasars. We consider a sample of 147,000 quasars from the extended Baryon Oscillation Spectroscopic Survey (eBOSS) distributed over 2044 square degrees with redshifts 0.8 < z < 2.2 and measure their spherically-averaged clustering in both configuration and Fourier space. Our observational dataset and the 1400 simulated realizations of the dataset allow us to detect a preference for BAO that is greater than 2.5σ. We determine the spherically averaged BAO distance to z = 1.52 to 4.4 per cent precision: DV (z = 1.52) = 3855 ± 170 (rd/rd,fid) Mpc. This is the first time the location of the BAO feature has been measured between redshifts 1 and 2. Our result is fully consistent with the prediction obtained by extrapolating the Planck flat ΛCDM best-fit cosmology. All of our results are consistent with basic large-scale structure (LSS) theory, confirming quasars to be a re...
Monthly Notices of the Royal Astronomical Society, 2017
We present a measurement of the linear growth rate of structure, f, from the Sloan Digital Sky Su... more We present a measurement of the linear growth rate of structure, f, from the Sloan Digital Sky Survey III (SDSS-III) Baryon Oscillation Spectroscopic Survey (BOSS) Data Release 12 (DR12) using convolution Lagrangian perturbation theory (CLPT) with Gaussian streaming redshift space distortions (GSRSD) to model the two-point statistics of BOSS galaxies in DR12. The BOSS-DR12 data set includes 1198 006 massive galaxies spread over the redshift range 0.2 < z < 0.75. These galaxy samples are categorized in three redshift bins. Using CLPT-GSRSD in our analysis of the combined sample of the three redshift bins, we report measurements of fσ 8 for the three redshift bins. We find fσ 8 = 0.430 ± 0.054 at z eff = 0.38, fσ 8 = 0.452 ± 0.057 at z eff = 0.51 and fσ 8 = 0.457 ± 0.052 at z eff = 0.61. Our results are consistent with the predictions of Planck cold dark matter-general relativity. Our constraints on the growth rates of structure in the Universe at different redshifts serve as a useful probe, which can help distinguish between a model of the Universe based on dark energy and models based on modified theories of gravity. This paper is part of a set that analyses the final galaxy clustering data set from BOSS. The measurements and likelihoods presented here are combined with others in Alam et al., to produce the final cosmological constraints from BOSS.
Monthly Notices of the Royal Astronomical Society, 2016
We present baryon acoustic oscillation (BAO) scale measurements determined from the clustering of... more We present baryon acoustic oscillation (BAO) scale measurements determined from the clustering of 1.2 million massive galaxies with redshifts 0.2 < z < 0.75 distributed over 9300 deg 2 , as quantified by their redshift-space correlation function. In order to facilitate these measurements, we define, describe, and motivate the selection function for galaxies in the final data release (DR12) of the SDSS III Baryon Oscillation Spectroscopic Survey (BOSS). This includes the observational footprint, masks for image quality and Galactic extinction, and weights to account for density relationships intrinsic to the imaging and spectroscopic portions of the survey. We simulate the observed systematic trends in mock galaxy samples and demonstrate that they impart no bias on BAO scale measurements and have a minor impact on the recovered statistical uncertainty. We measure transverse and radial BAO distance measurements in 0.2 < z < 0.5, 0.5 < z < 0.75, and (overlapping) 0.4 < z < 0.6 redshift bins. In each redshift bin, we obtain a precision that is 2.7 per cent or better on the radial distance and 1.6 per cent or better on the transverse distance. The combination of the redshift bins represents 1.8 per cent precision on the radial distance and 1.1 per cent precision on the transverse distance. This paper is part of a set that analyses the final galaxy clustering data set from BOSS. The measurements and likelihoods presented here are combined with others in Alam et al. to produce the final cosmological constraints from BOSS.
Monthly Notices of the Royal Astronomical Society, Jan 9, 2019
Marked correlation functions, which are sensitive to the clustering of galaxies in different envi... more Marked correlation functions, which are sensitive to the clustering of galaxies in different environments, have been proposed as constraints on modified gravity models. We present measurements of the marked correlation functions of galaxies in redshift space using 361,761 LOWZ (z eff = 0.32) galaxies from the Sloan Digital Sky Survey III (SDSS III) Baryon Oscillation Spectroscopic Survey (BOSS) Data Release 12 (DR12) and compare them to CDM+General Relativity simulations. We apply mass cuts to find the best match between the redshift space autocorrelation function of subhaloes in the simulation and in the observations. We then compare the marked correlation functions, finding no significant evidence for deviations of the marked correlation functions of LOWZ galaxies from CDM on scales 6 h −1 Mpc ≤ s ≤ 69 h −1 Mpc. The constraining power of marked correlation functions in our analysis is limited by our ability to model the autocorrelation function of galaxies on small scales including the effect of redshift distortions. The statistical errors are well below the differences seen between marked correlation functions of f(R) gravity models and CDM in recent publications (Armijo et al., Hernández-Aguayo et al.) indicating that improved future theoretical analyses should be able to rule out some models definitively.
Monthly Notices of the Royal Astronomical Society, Mar 28, 2017
We develop a new computationally efficient methodology called double-probe analysis with the aim ... more We develop a new computationally efficient methodology called double-probe analysis with the aim of minimizing informative priors (those coming from extra probes) in the estimation of cosmological parameters. Using our new methodology, we extract the dark energy model-independent cosmological constraints from the joint data sets of the Baryon Oscillation Spectroscopic Survey (BOSS) galaxy sample and Planck cosmic microwave background (CMB) measurements. We measure the mean values and covariance matrix of {R, l a , b h 2 , n s , log(A s), k , H(z), D A (z), f(z)σ 8 (z)}, which give an efficient summary of the Planck data and two-point statistics from the BOSS galaxy sample. The CMB shift parameters are R = m H 2 0 r(z *) and l a = πr(z *)/r s (z *), where z * is the redshift at the last scattering surface, and r(z *) and r s (z *) denote our comoving distance to the z * and sound horizon at z * , respectively; b is the baryon fraction at z = 0. This approximate methodology guarantees that we will not need to put informative priors on the cosmological parameters that galaxy clustering is unable to constrain, i.e. b h 2 and n s. The main advantage is that the computational time required for extracting these parameters is decreased by a factor of 60 with respect to exact full-likelihood analyses. The results obtained show no tension with the flat cold dark matter (CDM) cosmological paradigm. By comparing with the full-likelihood exact analysis with fixed dark energy models, on one hand we demonstrate that the double-probe method provides robust cosmological parameter constraints that can be conveniently used to study dark energy models, and on the other hand we provide a reliable set of measurements assuming dark energy models to be used, for example, in distance estimations. We extend our study to measure the sum of the neutrino mass using different methodologies, including double-probe analysis (introduced in this study), full-likelihood analysis and single-probe analysis. From full-likelihood
Monthly Notices of the Royal Astronomical Society, Jun 30, 2017
We analyse the broad-range shape of the monopole and quadrupole correlation functions of
Monthly Notices of the Royal Astronomical Society, Apr 11, 2017
We present a measurement of the linear growth rate of structure, f from the Sloan Digital Sky Sur... more We present a measurement of the linear growth rate of structure, f from the Sloan Digital Sky Survey III (SDSS III) Baryon Oscillation Spectroscopic Survey (BOSS) Data Release 12 (DR12) using Convolution Lagrangian Perturbation Theory (CLPT) with Gaussian Streaming Redshift-Space Distortions (GSRSD) to model the two point statistics of BOSS galaxies in DR12. The BOSS-DR12 dataset includes 1,198,006 massive galaxies spread over the redshift range 0.2 < z < 0.75. These galaxy samples are categorized in three redshift bins. Using CLPT-GSRSD in our analysis of the combined sample of the three redshift bins, we report measurements of f σ 8 for the three redshift bins. We find f σ 8 = 0.430 ± 0.054 at z eff = 0.38, f σ 8 = 0.452 ± 0.057 at z eff = 0.51 and f σ 8 = 0.457 ± 0.052 at z eff = 0.61. Our results are consistent with the predictions of Planck ΛCDM-GR. Our constraints on the growth rates of structure in the Universe at different redshifts serve as a useful probe, which can help distinguish between a model of the Universe based on dark energy and models based on modified theories of gravity. This paper is part of a set that analyses the final galaxy clustering dataset from BOSS. The measurements and likelihoods presented here are combined with others in Alam et al. (2016) to produce the final cosmological constraints from BOSS.
Monthly Notices of the Royal Astronomical Society, Mar 28, 2017
We present cosmological results from the final galaxy clustering data set of the Baryon Oscillati... more We present cosmological results from the final galaxy clustering data set of the Baryon Oscillation Spectroscopic Survey, part of the Sloan Digital Sky Survey III. Our combined galaxy sample comprises 1.2 million massive galaxies over an effective area of 9329 deg 2 and volume of 18.7 Gpc 3 , divided into three partially overlapping redshift slices centred at effective redshifts 0.38, 0.51 and 0.61. We measure the angular diameter distance D M and Hubble parameter H from the baryon acoustic oscillation (BAO) method, in combination with a cosmic microwave background prior on the sound horizon scale, after applying reconstruction to reduce non-linear effects on the BAO feature. Using the anisotropic clustering of the Hubble Fellow.
arXiv (Cornell University), Jul 11, 2016
We present a measurement of the linear growth rate of structure, f from the Sloan Digital Sky Sur... more We present a measurement of the linear growth rate of structure, f from the Sloan Digital Sky Survey III (SDSS III) Baryon Oscillation Spectroscopic Survey (BOSS) Data Release 12 (DR12) using Convolution Lagrangian Perturbation Theory (CLPT) with Gaussian Streaming Redshift-Space Distortions (GSRSD) to model the two point statistics of BOSS galaxies in DR12. The BOSS-DR12 dataset includes 1,198,006 massive galaxies spread over the redshift range 0.2 < z < 0.75. These galaxy samples are categorized in three redshift bins. Using CLPT-GSRSD in our analysis of the combined sample of the three redshift bins, we report measurements of f σ 8 for the three redshift bins. We find f σ 8 = 0.430 ± 0.054 at z eff = 0.38, f σ 8 = 0.452 ± 0.057 at z eff = 0.51 and f σ 8 = 0.457 ± 0.052 at z eff = 0.61. Our results are consistent with the predictions of Planck ΛCDM-GR. Our constraints on the growth rates of structure in the Universe at different redshifts serve as a useful probe, which can help distinguish between a model of the Universe based on dark energy and models based on modified theories of gravity. This paper is part of a set that analyses the final galaxy clustering dataset from BOSS. The measurements and likelihoods presented here are combined with others in Alam et al. (2016) to produce the final cosmological constraints from BOSS.
Monthly Notices of the Royal Astronomical Society, Oct 11, 2017
We present measurements of the Baryon Acoustic Oscillation (BAO) scale in redshift-space using th... more We present measurements of the Baryon Acoustic Oscillation (BAO) scale in redshift-space using the clustering of quasars. We consider a sample of 147,000 quasars from the extended Baryon Oscillation Spectroscopic Survey (eBOSS) distributed over 2044 square degrees with redshifts 0.8 < z < 2.2 and measure their spherically-averaged clustering in both configuration and Fourier space. Our observational dataset and the 1400 simulated realizations of the dataset allow us to detect a preference for BAO that is greater than 2.8σ. We determine the spherically averaged BAO distance to z = 1.52 to 3.8 per cent precision: D V (z = 1.52) = 3843 ± 147 (r d /r d,fid) Mpc. This is the first time the location of the BAO feature has been measured between redshifts 1 and 2. Our result is fully consistent with the prediction obtained by extrapolating the Planck flat ΛCDM best-fit cosmology. All of our results are consistent with basic large-scale structure (LSS) theory, confirming quasars to be a reliable tracer of LSS, and provide a starting point for numerous cosmological tests to be performed with eBOSS quasar samples. We combine our result with previous, independent, BAO distance measurements to construct an updated BAO distance-ladder. Using these BAO data alone and marginalizing over the length of the standard ruler, we find Ω Λ > 0 at 6.6σ significance when testing a ΛCDM model with free curvature.
Classical and Quantum Gravity, Dec 3, 2012
We calculate the degree of horizon smoothness of multi-M2-brane solution with branes along a comm... more We calculate the degree of horizon smoothness of multi-M2-brane solution with branes along a common axis. We find that the metric is generically only thrice continuously differentiable at any of the horizons. The four-form field strength is found to be only twice continuously differentiable. We work with Gaussian null-like coordinates which are obtained by solving geodesic equations for multi-M2 brane geometry. We also find different, exact coordinate transformations which take the metric from isotropic coordinates to coordinates in which metric is thrice differentiable at the horizon. Both methods give the same result that the multi-M2 brane metric is only thrice differentiable at the horizon. 1 A Series expansions for r(λ, Θ) and θ(λ, Θ) 17 B Components of the C 3 metric 19 C Components of A [3] 20 D Equation of motion 22
The Wide Field Infrared Survey Telescope (WFIRST), with its field of view and high sensitivity wi... more The Wide Field Infrared Survey Telescope (WFIRST), with its field of view and high sensitivity will make surveys of cosmological large-scale structure possible at high redshifts. We investigate the possibility of detecting Baryon Acoustic Oscillations (BAO) at redshifts z > 7.6 for use as a standard ruler. We use data from the hydrodynamic simulation BlueTides in conjunction with the gigaparsec-scale Outer Rim simulation and a model for patchy reionization to create mock WFIRST High Latitude Survey grism data for Lyman-α emission line selected galaxies at redshifts z = 7.4 to z = 10, covering 2280 square degrees. We measure the monopoles of galaxies in the mock catalogues and fit the BAO features. We find that for a line flux of L = 7×10 −17 erg/s/cm 2 , the 5σ detection limit for the current design, the BAO feature is partially detectable (measured in three out of four survey quadrants analysed independently). The resulting root mean square error on the angular diameter distance to z = 7.7 is 7.9%. If we improve the detection sensitivity by a factor of two (i.e. L = 3.5 × 10 −17 erg/s/cm 2), the distance error reduces to 1.4%. We caution that many more factors are yet to be modelled, including dust obscuration, the damping wing due to the intergalactic medium, and low redshift interlopers. If these issues do not strongly affect the results, or different observational techniques (such as use of multiple lines) can mitigate them, WFIRST or similar instruments may be able to constrain the angular diameter distance to the high redshift Universe.
Monthly Notices of the Royal Astronomical Society, 2019
Marked correlation functions, which are sensitive to the clustering of galaxies in different envi... more Marked correlation functions, which are sensitive to the clustering of galaxies in different environments, have been proposed as constraints on modified gravity models. We present measurements of the marked correlation functions of galaxies in redshift space using 361,761 LOWZ (z eff = 0.32) galaxies from the Sloan Digital Sky Survey III (SDSS III) Baryon Oscillation Spectroscopic Survey (BOSS) Data Release 12 (DR12) and compare them to CDM+General Relativity simulations. We apply mass cuts to find the best match between the redshift space autocorrelation function of subhaloes in the simulation and in the observations. We then compare the marked correlation functions, finding no significant evidence for deviations of the marked correlation functions of LOWZ galaxies from CDM on scales 6 h −1 Mpc ≤ s ≤ 69 h −1 Mpc. The constraining power of marked correlation functions in our analysis is limited by our ability to model the autocorrelation function of galaxies on small scales including the effect of redshift distortions. The statistical errors are well below the differences seen between marked correlation functions of f(R) gravity models and CDM in recent publications (Armijo et al., Hernández-Aguayo et al.) indicating that improved future theoretical analyses should be able to rule out some models definitively.
Classical and Quantum Gravity, 2012
We calculate the degree of horizon smoothness of multi-M2-brane solution with branes along a comm... more We calculate the degree of horizon smoothness of multi-M2-brane solution with branes along a common axis. We find that the metric is generically only thrice continuously differentiable at any of the horizons. The four-form field strength is found to be only twice continuously differentiable. We work with Gaussian null-like coordinates which are obtained by solving geodesic equations for multi-M2 brane geometry. We also find different, exact coordinate transformations which take the metric from isotropic coordinates to coordinates in which metric is thrice differentiable at the horizon. Both methods give the same result that the multi-M2 brane metric is only thrice differentiable at the horizon. 1 A Series expansions for r(λ, Θ) and θ(λ, Θ) 17 B Components of the C 3 metric 19 C Components of A [3] 20 D Equation of motion 22
Monthly Notices of the Royal Astronomical Society, 2020
The Nancy Grace Roman Space Telescope (RST), with its field of view and high sensitivity will mak... more The Nancy Grace Roman Space Telescope (RST), with its field of view and high sensitivity will make surveys of cosmological large-scale structure possible at high redshifts. We investigate the possibility of detecting baryon acoustic oscillations (BAO) at redshifts z > 7.6 for use as a standard ruler. We use data from the hydrodynamic simulation bluetides in conjunction with the gigaparsec-scale Outer Rim simulation and a model for patchy reionization to create mock RST High Latitude Survey grism data for Lyman α emission line selected galaxies at redshifts z = 7.4 to z = 10, covering 2280 deg2. We measure the monopoles of galaxies in the mock catalogues and fit the BAO features. We find that for a line flux of $L = 7\times 10^{-17} \ {\rm erg\, s^{-1}\, cm}^{-2}$, the 5σ detection limit for the current design, the BAO feature is partially detectable (measured in three out of four survey quadrants analysed independently). The resulting root mean square error on the angular diamete...
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Papers by Siddharth Satpathy