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P. Mukherjee

Publications and source records attributed to P. Mukherjee.

At least 19 recordsLinked to original sources
arXiv2026

Validation of the DESI DR2 Ly$\alpha$ forest full-shape analysis

We present the validation of the Dark Energy Spectroscopic Instrument (DESI) Data Release 2 (DR2) Lyman-$\alpha$ (Ly$\alpha$) forest full-shape analysis. This analysis combines three-dimensional Ly$\alpha$ forest auto-correlations and cross-correlations with quasars to extract information from both the baryon acoustic oscillation (BAO) feature and the broadband clustering signal, with primary emphasis on the Alcock-Paczynski (AP) measurement. Compared to the DESI DR1 analysis, the DR2 validation uses substantially larger and more realistic mock datasets, including CoLoRe 2LPT and AbacusSummit Ly$\alpha$ forest simulations. The modeling framework is also improved through analytic marginalization over small scales ($<10$ $h^{-1}$Mpc) and the impact of ultraviolet background fluctuations. The validation program was completed prior to unblinding and defines quantitative requirements for the cosmological parameters of interest, which are evaluated using hundreds of mock realizations. We further test the analysis through independent fits to the auto- and cross-correlations, multiple catalog splits, and a broad suite of analysis and modeling variations applied to both mocks and blinded observational data. We find that the BAO and AP parameters satisfy all validation requirements and remain stable across all tests. In contrast, mock studies reveal a significant bias in the inferred growth-rate parameter $f\sigma_8$, leading us to exclude this measurement from the final analysis. The consistency across mocks, data splits, and robustness tests demonstrates that the DR2 Ly$\alpha$ full-shape analysis provides a reliable and substantially improved broadband AP measurement over previous Ly$\alpha$ forest studies.

astro-ph.CO↗
arXiv2026

CoLoRe-2LPT: Lyman-$\alpha$ mock catalogues for the validation of DESI cosmological analyses

The Lyman-$\alpha$ (Ly$\alpha$) forest has become a crucial probe for studying the large-scale structure of the universe at high redshift ($z > 2$), providing powerful constraints on Baryon Acoustic Oscillations (BAO) and the full-shape (FS) clustering of matter. As a key ingredient for upcoming BAO and FS analyses, we present a new generation of fast cosmological Ly$\alpha$ mocks based on second-order Lagrangian perturbation theory (2LPT). These new mocks significantly improve upon previous log-normal approaches, both at accurately capturing small scale clustering and at recovering the non-linear broadening of the BAO peak. They are able to reproduce Ly$\alpha$ statistics within $10\%$ of the latest DESI measurement; including the Ly$\alpha$ bias and the redshift-space distortion $\beta$ parameter, mean transmitted flux, and 1D power spectrum. The corresponding quasar (QSO) clustering is also improved with respect to previous approaches, calibrated against high-resolution Abacus simulations, recovering the observational QSO linear bias to less than $5\%$ and improving redshift-space distortions via 2LPT velocities and the addition of Fingers-of-God effects. Furthermore, these mocks incorporate high column density systems and metal lines, allowing us to explore the effects and systematics induced by these astrophysical contaminants. This new set of mocks has been key for enhancing the modeling and validation of the DESI DR2 Ly$\alpha$ full shape cosmological analysis. This work provides a physically motivated and computationally efficient tool for simulating current and next-generation Ly$\alpha$ surveys and validating FS and BAO analysis.

astro-ph.CO↗
arXiv2026

Lyman-$\alpha$ forest holography: 3D predictions from 1D measurements

Cosmological analyses of Lyman-$\alpha$ forest clustering rely on either one-dimensional correlations along individual sightlines or three-dimensional correlations between different sightlines. Because these observables probe the matter distribution on very different scales, they have traditionally been analyzed independently. In this work, we bridge this gap using ForestFlow, an emulator trained on a suite of cosmological hydrodynamical simulations that provides a unified description of Lyman-$\alpha$ forest clustering from linear to nonlinear scales. This framework enables us to determine the range of three-dimensional clustering models compatible with the DESI one-dimensional flux power spectrum ($P_{\rm 1D}$). The resulting predictions successfully reproduce the large-scale clustering measured by the DESI BAO analysis and provide physically motivated priors on nonlinear clustering that are used in a companion paper presenting the full-shape analysis of the DESI DR2 Lyman-$\alpha$ forest. We validate our methodology using the large-volume, high-resolution hydrodynamical simulation ACCEL-2, demonstrating excellent agreement across the full range of scales considered. Finally, we combine constraints from the $P_{\rm 1D}$ and BAO analyses on the parameter combinations $b_\delta \sigma_8$ and $b_\eta f \sigma_8$, finding that the two probes provide comparable constraining power while exhibiting complementary parameter degeneracies. Our results establish a direct connection between one- and three-dimensional Lyman-$\alpha$ forest measurements through ForestFlow, an approach we term Lyman-$\alpha$ holography by analogy with the reconstruction of higher-dimensional structure from lower-dimensional information.

astro-ph.CO↗
arXiv2026

CoLoRFulNNLO for color-singlet processes: An update on NNLOCAL

We give an update on the status of NNLOCAL, a parton-level Monte Carlo program implementing the extension of the completely local subtraction scheme CoLoRFulNNLO to color-singlet production in hadron-hadron collisions. The construction of the counterterms in our scheme is generic, being based on the standard IR factorization formulae of QCD. Furthermore, the integration of the counterterms over the phase space of unresolved emissions is performed fully analytically, allowing for good control of the numerical stability of our predictions. We validate our method by computing NNLO corrections to fully differential cross sections for the LHC.

hep-ph↗
arXiv2026

Early growth of massive black holes in dynamical dark energy models with negative cosmological constant

Recent results from combined cosmological probes indicate that the Dark Energy component of the Universe could be dynamical. The simplest explanation envisages the presence of a quintessence field rolling into a potential, where the Dark Energy energy density parameter $\Omega_{DE}=\Omega_{\Lambda}+\Omega_{x}$ results from the contribution of the ground state energy $\Omega_{\Lambda}$ and the scalar field energy $\Omega_{x}$. Provided that $\Omega_{DE}\approx 0.7$, negative values of $\Omega_{\Lambda}$ can be consistent with current measurements from cosmological probes, and could help in explaining the large abundance of bright galaxies observed by JWST at $z> 10$, largely exceeding the pre-JWST expectations in a $\Lambda CDM$ Universe. Here we explore to what extent such a scenario can account also for the early presence of massive Black Holes (BHs) with masses $M_{BH}\gtrsim 10^7\,M_{\odot}$ observed at $z\gtrsim 8$, and for the large over-abundance of AGN with respect to pre-JWST expectations. Our aim is not to provide a detailed description of BH growth, but rather to compute the maximal BH growth that can occur in cosmological models with negative $\Omega_{\Lambda}$ under the simple assumption of Eddington-limited accretion onto initial light Black Hole seeds with mass $M_{seed}\sim 10^2\,M_{\odot}$ originated from PopIII stars. To this aim we develop a simple analytic framework to connect the growth of dark matter halos to the maximal growth of BHs within the above assumptions. We show such models can account for present observations assuming values of $\Omega_{\Lambda}\approx -1$, simultaneously boosting both galaxy and AGN number counts without invoking any additional physics. This would allow us to trace the observed excess of bright and massive galaxies and the early formation of massive Black Holes and the abundance of AGN to the same cosmological origin.

astro-ph.CO↗
arXiv2024

NNLOCAL: completely local subtractions for color-singlet production in hadron collisions

We present NNLOCAL, a proof-of-concept parton-level Monte Carlo program implementing the extension of the completely local subtraction scheme CoLoRFulNNLO to the case of color-singlet production in hadron collisions. We have built general local subtraction terms that regularize all single and double unresolved infrared singularities in real radiation phase space. The subtractions are then integrated fully analytically to the required order in the parameter of dimensional regularization. Combining the integrated counterterms with the virtual contributions we demonstrate the cancellation of all infrared poles explicitly. We validate our procedure by computing the fully differential cross section for the production of a Higgs boson at the LHC in an effective field theory with gluons only. Our code provides the first public implementation of a completely local analytic subtraction scheme at next-to-next-to-leading order accuracy.

hep-ph↗
arXiv2024

CoLoRFul for hadron collisions: Integrating the counterterms

In order to numerically compute scattering cross sections in QCD, one needs to deal with various kinematic divergences that appear at intermediate stages of the calculation. One way of doing this is by setting up an IR subtraction scheme. In this talk we give an update on the status of extending the CoLoRFul subtraction scheme, which has been successfully used in the past for processes with only final-state hadrons, to hadron-hadron collisions. In particular we discuss the analytic computation of the integrated counterterms.

hep-ph↗
arXiv2020

Sample Dependence of Magnetism in the Next Generation Cathode Material LiNi$_{0.8}$Mn$_{0.1}$Co$_{0.1}$O$_2$

We present a structural and magnetic study on two batches of polycrystalline LiNi$_{0.8}$Mn$_{0.1}$Co$_{0.1}$O$_2$ (commonly known as Li NMC 811), a Ni-rich Li ion battery cathode material, using elemental analysis, X-ray and neutron diffraction, magnetometry, and polarised neutron scattering measurements. We find that the samples, labelled S1 and S2, have the composition Li$_{1-x}$Ni$_{0.9+x-y}$Mn$_y$Co$_{0.1}$O$_2$, with $x = 0.025(2)$, $y = 0.120(2)$ for S1 and $x = 0.002(2)$, $y = 0.094(2)$ for S2, corresponding to different concentrations of magnetic ions and excess Ni$^{2+}$ in the Li$^+$layers. Both samples show a peak in the zero-field cooled (ZFC) dc susceptibility at 8.0(2) K but the temperature at which the ZFC and FC (field-cooled) curves deviate is substantially different: 64(2) K for S1 and 122(2) K for S2. Ac susceptibility measurements show that the transition for S1 shifts with frequency whereas no such shift is observed for S2 within the resolution of our measurements. Our results demonstrate the sample dependence of magnetic properties in Li NMC 811, consistent with previous reports on the parent material LiNiO$_2$. We further establish that a combination of experimental techniques are necessary to accurately determine the chemical composition of next generation battery materials with multiple cations.

cond-mat.mtrl-sci↗
arXiv2017

Relieving the frustration through Mn$^{3+}$ substitution in Holmium Gallium Garnet

We present a study on the impact of Mn$^{3+}$ substitution in the geometrically frustrated Ising garnet Ho$_3$Ga$_5$O$_{12}$ using bulk magnetic measurements and low temperature powder neutron diffraction. We find that the transition temperature, $T_N$ = 5.8 K, for Ho$_3$MnGa$_4$O$_{12}$ is raised by almost 20 when compared to Ho$_3$Ga$_5$O$_{12}$. Powder neutron diffraction on Ho$_3$Mn$_x$Ga$_{5-x}$O$_{12}$ ($x$ = 0.5, 1) below $T_N$ shows the formation of a long range ordered ordered state with $\mathbf{k}$ = (0,0,0). Ho$^{3+}$ spins are aligned antiferromagnetically along the six crystallographic axes with no resultant moment while the Mn$^{3+}$ spins are oriented along the body diagonals, such that there is a net moment along [111]. The magnetic structure can be visualised as ten-membered rings of corner-sharing triangles of Ho$^{3+}$ spins with the Mn$^{3+}$ spins ferromagnetically coupled to each individual Ho$^{3+}$ spin in the triangle. Substitution of Mn$^{3+}$ completely relieves the magnetic frustration with $f = θ_{CW}/T_N \approx 1.1$ for Ho$_3$MnGa$_4$O$_{12}$.

cond-mat.str-el↗
arXiv2017

Sensitivity of magnetic properties to chemical pressure in lanthanide garnets $Ln_3A_2X_3\text{O}_{12}$, $Ln$ = Gd, Tb, Dy, Ho, $A$ = Ga, Sc, In, Te, $X$ = Ga, Al, Li

A systematic study of the structural and magnetic properties of three-dimensionally frustrated lanthanide garnets $Ln_3A_2X_3\text{O}_{12}$, $Ln$ = Gd, Tb, Dy, Ho, $A$ = Ga, Sc, In, Te, $X$ = Ga, Al, Li is presented. Garnets with $Ln$ = Gd show magnetic behaviour consistent with isotropic Gd$^{3+}$ spins; no magnetic ordering is observed for T $\geq$ 0.4 K. Magnetic ordering features are seen for garnets with $Ln$ = Tb, Dy, Ho in the temperature range 0.4 < T < 2.5 K, however the nature of the magnetic ordering varies for the different $Ln$ as well as for different combinations of $A$ and $X$. The changes in magnetic behaviour can be explained by tuning of the magnetic interactions and changes in the single-ion anisotropy. The change in magnetic entropy is evaluated from isothermal magnetisation measurements to characterise the magnetocaloric effect in these materials. Among the Gd garnets, the maximum change in magnetic entropy per mole (15.45 J K$^{-1}$ mol$_{\text{Gd}}^{-1}$) is observed for Gd$_3$Sc$_2$Ga$_3$O$_{12}$ at 2 K, in a field of 9 T. The performance of Dy$_3$Ga$_5$O$_{12}$ as a magnetocaloric material surpasses the other garnets with $Ln$ = Tb, Dy, Ho.

cond-mat.str-el↗
arXiv2015

In situ XRD studies of the process dynamics during annealing in cold rolled copper

The dynamics of the release of stored energy during annealing along two different crystallographic planes i.e.{111} and {220} in deformed copper have been investigated using in-situ X-ray diffraction measurements at 458K and 473K respectively. The study has been carried out on 50% and 80% rolled Cu sheets. The microstructures of the rolled samples have been characterised using optical microscope and Electron Back Scattered Diffraction measurements. The microstructural parameters were evaluated using Scherrer equation and the modified Rietveld technique from X-ray diffractogram. The stored energy along different planes were determined using the modified Stibitz formula from the X-ray peak broadening and the bulk stored energy has been evaluated using differential scanning calorimetry. The process dynamics of recovery and recrystallization as observed through the release of stored energy has been modelled as a second order and first order process respectively.

cond-mat.mtrl-sci↗
arXiv2014

Understanding the Effect of Uniaxial Tensile Strain on the Early Stages of Sensitization in AISI 304 Austenitic Stainless Steel

In the present study, an attempt has been made to understand the effect of different competing mechanisms controlling the overall degree of sensitization (DOS) of deformed austenitic stainless steel at the early stage of sensitization. The Double Loop Electrochemical Potentiokinetic Reactivation (DL-EPR) studies were performed to characterize the Degree of Sensitization (DOS) as functions of pre-defined strain and sensitization temperature. X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) were used to explain the phenomena qualitatively. A non monotonous behaviour in the variation of DOS has been observed with deformation and sensitization temperature. The presence of Deformation Induced Martensites (DIM) and their transformation into tempered martensites (alpha + Fe3C) at higher temperatures was found to play major roles in controlling the overall sensitization and desensitization processes.

cond-mat.mtrl-sci↗
arXiv2012

Supernova Simulations and Strategies For the Dark Energy Survey

We present an analysis of supernova light curves simulated for the upcoming Dark Energy Survey (DES) supernova search. The simulations employ a code suite that generates and fits realistic light curves in order to obtain distance modulus/redshift pairs that are passed to a cosmology fitter. We investigated several different survey strategies including field selection, supernova selection biases, and photometric redshift measurements. Using the results of this study, we chose a 30 square degree search area in the griz filter set. We forecast 1) that this survey will provide a homogeneous sample of up to 4000 Type Ia supernovae in the redshift range 0.05<z<1.2, and 2) that the increased red efficiency of the DES camera will significantly improve high-redshift color measurements. The redshift of each supernova with an identified host galaxy will be obtained from spectroscopic observations of the host. A supernova spectrum will be obtained for a subset of the sample, which will be utilized for control studies. In addition, we have investigated the use of combined photometric redshifts taking into account data from both the host and supernova. We have investigated and estimated the likely contamination from core-collapse supernovae based on photometric identification, and have found that a Type Ia supernova sample purity of up to 98% is obtainable given specific assumptions. Furthermore, we present systematic uncertainties due to sample purity, photometric calibration, dust extinction priors, filter-centroid shifts, and inter-calibration. We conclude by estimating the uncertainty on the cosmological parameters that will be measured from the DES supernova data.

astro-ph.CO↗
arXiv2011

COrE (Cosmic Origins Explorer) A White Paper

COrE (Cosmic Origins Explorer) is a fourth-generation full-sky, microwave-band satellite recently proposed to ESA within Cosmic Vision 2015-2025. COrE will provide maps of the microwave sky in polarization and temperature in 15 frequency bands, ranging from 45 GHz to 795 GHz, with an angular resolution ranging from 23 arcmin (45 GHz) and 1.3 arcmin (795 GHz) and sensitivities roughly 10 to 30 times better than PLANCK (depending on the frequency channel). The COrE mission will lead to breakthrough science in a wide range of areas, ranging from primordial cosmology to galactic and extragalactic science. COrE is designed to detect the primordial gravitational waves generated during the epoch of cosmic inflation at more than $3σ$ for $r=(T/S)>=10^{-3}$. It will also measure the CMB gravitational lensing deflection power spectrum to the cosmic variance limit on all linear scales, allowing us to probe absolute neutrino masses better than laboratory experiments and down to plausible values suggested by the neutrino oscillation data. COrE will also search for primordial non-Gaussianity with significant improvements over Planck in its ability to constrain the shape (and amplitude) of non-Gaussianity. In the areas of galactic and extragalactic science, in its highest frequency channels COrE will provide maps of the galactic polarized dust emission allowing us to map the galactic magnetic field in areas of diffuse emission not otherwise accessible to probe the initial conditions for star formation. COrE will also map the galactic synchrotron emission thirty times better than PLANCK. This White Paper reviews the COrE science program, our simulations on foreground subtraction, and the proposed instrumental configuration.

astro-ph.CO↗
arXiv2010

Temperature Dependence of the Dynamics of Portevin-Le Chatelier Effect in Al-2.5%Mg alloy

Tensile tests were carried out by deforming polycrystalline samples of Al-2.5%Mg alloy at four different temperatures in an intermediate strain rate regime of 2x10-4s-1 to 2x10-3s-1. The Portevin-Le Chatelier (PLC) effect was observed throughout the strain rate and temperature region. The mean cumulative stress drop magnitude and the mean reloading time exhibit an increasing trend with temperature which is attributed to the enhanced solute diffusion at higher temperature. The observed stress-time series data were analyzed using the nonlinear dynamical methods. From the analyses, we could establish the presence of deterministic chaos in the PLC effect throughout the temperature regime. The dynamics goes to higher dimension at a sufficiently high temperature of 425K but the complexity of the dynamics is not affected by the temperature.

cond-mat.mtrl-sci↗
arXiv2010

In situ studies of evolution of microstructure with temperature in heavily deformed Ti-modified austenitic stainless steel by X-ray Diffraction technique

The mechanism of the evolution of the deformed microstructure at the earliest stage of annealing where the existence of the lowest length scale substructure paves the way to the formation of the so-called subgrains, has been studied for the first time. The study has been performed at high temperature on heavily deformed Ti-modified austenitic stainless steel using X-ray diffraction technique. Significant changes were observed in the values of the domain size, both with time and temperature. Two different types of mechanism have been proposed to be involved during the microstructural evolution at the earliest stages of annealing. The nature of the growth of domains with time at different temperatures has been modelled using these mechanisms. High-resolution transmission electron microscopy has been used to view the microstructure of the deformed and annealed sample and the results have been corroborated successfully with those found from the X-ray diffraction techniques.

cond-mat.mtrl-sci↗
arXiv2010

Anomalous interaction between dislocations and ultra-small voids

We carry out the molecular statics simulations of depinning of an edge dislocation at voids of diameters of the order of ~1 nm. We show that the dislocation-void interactions are non-trivial as the applied shear load is found to enhance the pinning strength of the nanovoid itself. This leads to the surprising observation of multiple CRSS values for a given nanovoid.

cond-mat.mtrl-sci↗