Baryon Fields Research Articles

Analysis of 2S singly heavy baryons in HQET

In this paper, we have employed HQET to determine the masses of radially excited ([Formula: see text]) S-wave charm and bottom baryons. The HQET Lagrangian containing the non-perturbative parameters is shown with heavy baryon fields. The non-perturbative parameters, couplings, and decay widths are also studied for the S-wave singly heavy baryons. The HQET parameters [Formula: see text], [Formula: see text] and [Formula: see text] are calculated for the ground state ([Formula: see text]) using the masses of S-wave baryons. The [Formula: see text] mass short-distance mass scheme is employed to estimate the heavy quark masses and non-perturbative parameters. The mass term ratios of [Formula: see text] and [Formula: see text] mesons and baryons containing parameters [Formula: see text] and [Formula: see text] are studied by varying the bottom quark mass. This analysis shows that heavy quarks behave the same inside mesons and baryons in both 1S and 2S states. The HQET symmetry of [Formula: see text] is used to find the parameters and masses for [Formula: see text] S-wave baryons. The variation of mass of 2S baryons with the non-perturbative parameters [Formula: see text] and [Formula: see text] is discussed. The Regge trajectories are also plotted in the [Formula: see text] plane using masses of [Formula: see text] and 2 charm and bottom baryons. The Regge trajectories are parallel and equidistant lines in the [Formula: see text] plane. We have also studied the strong decays of charm and bottom baryons for both [Formula: see text] and [Formula: see text] states. We have estimated the coupling constants [Formula: see text] and [Formula: see text] for [Formula: see text], and [Formula: see text] for [Formula: see text]. We have also shown the semi-electronic decay rates of charm baryons in the spectator heavy quark approximation for [Formula: see text], [Formula: see text], and [Formula: see text] transitions. The decay rates for [Formula: see text] transitions are of the same order as [Formula: see text] transitions. This analysis agrees well with the available theoretical and experimental data.

TensorFlow Hydrodynamics Analysis for Ly-[formula omitted] Simulations

We introduce the Python program THALAS (TensorFlow Hydrodynamics Analysis for Lyman-Alpha Simulations), which maps baryon fields (baryon density, temperature, and velocity) to Lyα optical depth fields in both real space and redshift space. Unlike previous Lyα codes, THALAS is fully differentiable, enabling a wide variety of potential applications for general analysis of hydrodynamical simulations and cosmological inference. To demonstrate THALAS’s capabilities, we apply it to the Lyα forest inversion problem: given a Lyα optical depth field, we reconstruct the corresponding real-space dark matter density field. Such applications are relevant to both cosmological and three-dimensional tomographic analyses of Lyman Alpha forest data.

Simulations of early structure formation: Properties of halos that host primordial star formation

Context. Population III (pop III) stars were born in halos characterised by a pristine gas composition. In such a halo, once the gas density reaches nH ∼ 1 cm−3, molecular cooling leads to the collapse of the gas and the birth of pop III stars. Halo properties, such as the chemical abundances, mass, and angular momentum can affect the collapse of the gas, thereby leading to the pop III initial mass function (IMF) of star formation. Aims. We want to study the properties of primordial halos and how halos that host early star formation differ from other types of halos. The aim of this study is to obtain a representative population of halos at a given redshift hosting a cold and massive gas cloud that enables the birth of the first stars. Methods. We investigated the growth of primordial halos in a ΛCDM Universe in a large cosmological simulation. We used the hydrodynamic code RAMSES and the chemical solver KROME to study halo formation with non-equilibrium thermochemistry. We then identified structures in the dark and baryonic matter fields, thereby linking the presence or absence of dense gas clouds to the mass and the physical properties of the hosting halos. Results. In our simulations, the mass threshold for a halo for hosting a cold dense gas cloud is ≃7 × 105 M⊙ and the threshold in the H2 mass fraction is found to be ≃2 × 10−4. This is in agreement with previous works. We find that the halo history and accretion rate play a minor role. Here, we present halos with higher HD abundances, which are shown to be colder, as the temperature in the range between 102 − 104 cm−3 depends on the HD abundance to a large extent. The higher fraction of HD is linked to the higher spin parameter that is seen for the dense gas.

The chiral Lagrangian with three flavors and large-N_c sum rules

We reconsider the chiral Lagrangian with three-flavor baryon fields. A systematic analysis of all low-energy constants (LEC) that contribute to the axial-vector and pseudoscalar currents in the baryon octet and decuplet fields at next-to-leading order in the inverse number of colors (1/N_c) of QCD is performed. We study the correlation function consisting of axial-vector and scalar currents as well. While there are 4 LEC relevant at leading chiral order, the number of relevant LEC at subleading order is 23. For those a leading order large-N_c analysis predicts 3 and 18 sum rules respectively. At the next accuracy level the number of sum rules is reduced to 2 and 8. Our results are illustrated by a tree-level analysis of available axial-vector coupling constants and strong decay widths of the baryon decuplet states.

Cosmology in Rastall theory with non-minimal matter coupling

In this paper we will consider cosmological implications of the Rastall theory with a non-minimal coupling with baryonic matter fields. In Rastall theory, the matter energy-momentum tensor is not conserved and the non-conservation is related to the curvature. We will generalize this relation to become dependent on both curvature and matter fields. Cosmology of the model shows more matter abundance compared to the model. We will show that the dynamical system of the model is the same as with an additional degree of freedom.

Simultaneous Dependence of Matter Clustering on Scale and Environment

In this work, we propose new statistical tools that are capable of characterizing the simultaneous dependence of dark matter and gas clustering on the scale and the density environment, and these are the environment-dependent wavelet power spectrum (env-WPS), the environment-dependent bias function (env-bias), and the environment-dependent wavelet cross-correlation function (env-WCC). These statistics are applied to the dark matter and baryonic gas density fields of the TNG100-1 simulation at redshifts of z=3.0-0.0, and to Illustris-1 and SIMBA at z = 0. The measurements of the env-WPSs suggest that the clustering strengths of both the dark matter and the gas increase with increasing density, while that of a Gaussian field shows no density dependence. By measuring the env-bias and env-WCC, we find that they vary significantly with the environment, scale, and redshift. A noteworthy feature is that at z = 0.0, the gas is less biased in denser environments of Δ ≳ 10 around 3 h Mpc−1, due to the gas reaccretion caused by the decreased AGN feedback strength at lower redshifts. We also find that the gas correlates more tightly with the dark matter in both the most dense and underdense environments than in other environments at all epochs. Even at z = 0, the env-WCC is greater than 0.9 in Δ ≳ 200 and Δ ≲ 0.1 at scales of k ≲ 10 h Mpc−1. In summary, our results support the local density environment having a non-negligible impact on the deviations between dark matter and gas distributions up to large scales.

Predicting the thermal Sunyaev–Zel’dovich field using modular and equivariant set-based neural networks

Theoretical uncertainty limits our ability to extract cosmological information from baryonic fields such as the thermal Sunyaev–Zel’dovich (tSZ) effect. Being sourced by the electron pressure field, the tSZ effect depends on baryonic physics that is usually modeled by expensive hydrodynamic simulations. We train neural networks on the IllustrisTNG-300 cosmological simulation to predict the continuous electron pressure field in galaxy clusters from gravity-only simulations. Modeling clusters is challenging for neural networks as most of the gas pressure is concentrated in a handful of voxels and even the largest hydrodynamical simulations contain only a few hundred clusters that can be used for training. Instead of conventional convolutional neural net (CNN) architectures, we choose to employ a rotationally equivariant DeepSets architecture to operate directly on the set of dark matter particles. We argue that set-based architectures provide distinct advantages over CNNs. For example, we can enforce exact rotational and permutation equivariance, incorporate existing knowledge on the tSZ field, and work with sparse fields as are standard in cosmology. We compose our architecture with separate, physically meaningful modules, making it amenable to interpretation. For example, we can separately study the influence of local and cluster-scale environment, determine that cluster triaxiality has negligible impact, and train a module that corrects for mis-centering. Our model improves by on analytic profiles fit to the same simulation data. We argue that the electron pressure field, viewed as a function of a gravity-only simulation, has inherent stochasticity, and model this property through a conditional-VAE extension to the network. This modification yields further improvement by , it is limited by our small training set however. We envision that our method will prove useful in problems beyond the specific one considered here 5 5We make our code publicly available at this URL. Data products, trained models, and hyperparameter SQL databases will be shared upon reasonable request..

Open charm mesons and charmonia in magnetized strange hadronic matter * *A.J.C.S acknowledges the support towards this work from the Department of Science and Technology, Government of India, via an INSPIRE fellowship (INSPIRE Code IF170745). AM acknowledges financial support from Department of Science and Technology (DST), Government of India (CRG/2018/002226)

We investigate the in-medium masses of open charm mesons (D( , ), ( , ), ( , )) and charmonium states ( , , , , ) in strongly magnetized isospin asymmetric strange hadronic matter using a chiral effective model. In the presence of a magnetic field, the number and scalar densities of charged baryons have contributions from Landau energy levels. The mass modifications of open charm mesons result from their interactions with nucleons, hyperons, and the scalar fields (the non-strange field σ, strange field ζ, and isovector field δ) in the presence of a magnetic field. The mass modifications of the charmonium states result from the modification of gluon condensates in a medium simulated by the variation in the dilaton field (χ) in the chiral effective model. The effects of finite quark masses are also incorporated in the trace of the energy-momentum tensor in quantum chromodynamics to investigate the mass shifts of charmonium states. The in-medium masses of open charm mesons and charmonia are observed to decrease with an increase in baryon density. The charged , , , and mesons have additional positive mass shifts due to Landau quantization in the presence of a magnetic field. The effects of the strangeness fraction are observed to be more dominant for mesons compared with D mesons. The mass shifts of charmonia are observed to be larger in hyperonic media compared with nuclear media when the effect of the finite quark mass term is neglected. These medium mass modifications can have observable consequences on the production of the open charm mesons and charmonia in high-energy asymmetric heavy-ion collision experiments.

Baryonic effective field theory for light hypernuclei

Light hypernuclei containing one or two Λ baryons are the subject of an ongoing experimental campaign aiming to study the spectrum of these systems, as well as the 2 and 3-body interaction between Λ hyperons and nucleons. Here we shortly review the theoretical study of these systems within the framework of baryonic effective field theory.

From EMBER to FIRE: predicting high resolution baryon fields from dark matter simulations with deep learning

ABSTRACT Hydrodynamic simulations provide a powerful, but computationally expensive, approach to study the interplay of dark matter and baryons in cosmological structure formation. Here, we introduce the EMulating Baryonic EnRichment (EMBER) Deep Learning framework to predict baryon fields based on dark matter-only simulations thereby reducing computational cost. EMBER comprises two network architectures, U-Net and Wasserstein Generative Adversarial Networks (WGANs), to predict 2D gas and H i densities from dark matter fields. We design the conditional WGANs as stochastic emulators, such that multiple target fields can be sampled from the same dark matter input. For training we combine cosmological volume and zoom-in hydrodynamical simulations from the Feedback in Realistic Environments (FIRE) project to represent a large range of scales. Our fiducial WGAN model reproduces the gas and H i power spectra within 10 per cent accuracy down to ∼10 kpc scales. Furthermore, we investigate the capability of EMBER to predict high resolution baryon fields from low resolution dark matter inputs through upsampling techniques. As a practical application, we use this methodology to emulate high-resolution H i maps for a dark matter simulation of a $L=100\, \text{Mpc}\, h^{ -1}$ comoving cosmological box. The gas content of dark matter haloes and the H i column density distributions predicted by EMBER agree well with results of large volume cosmological simulations and abundance matching models. Our method provides a computationally efficient, stochastic emulator for augmenting dark matter only simulations with physically consistent maps of baryon fields.

Non-minimal energy\u2013momentum squared gravity

We consider a gravitational theory with an additional non-minimal coupling between baryonic matter fields and geometry. The coupling is second order in the energy momentum tensor and can be seen as a generalization of the energy–momentum squared gravity model. We will add a constraint through a Lagrange multiplier to ensure the conservation of the energy–momentum tensor. Background cosmological implications together with its dynamical system analysis will be investigated in details. Also we will consider the growth of matter perturbations at first order, and estimate the model parameter from observations on H and also fsigma _8. We will show that the model parameter should be small and positive in 2sigma confidence interval. The theory is shown to be in a good agreement with observational data.

Turbulence-induced deviation between baryonic field and dark matter field in the spatial distribution of the Universe

ABSTRACT The cosmic baryonic fluid at low redshifts is similar to a fully developed turbulence. In this work, we use simulation samples produced by the hybrid cosmological hydrodynamical/N-body code, to investigate on what scale the deviation of spatial distributions between baryons and dark matter is caused by turbulence. For this purpose, we do not include the physical processes such as star formation, supernovae (SNe), and active galactic nucleus (AGN) feedback into our code, so that the effect of turbulence heating for IGM can be exhibited to the most extent. By computing cross-correlation functions rm(k) for the density field and rv(k) for the velocity field of both baryons and dark matter, we find that deviations between the two matter components for both density field and velocity field, as expected, are scale-dependent. That is, the deviations are the most significant at small scales and gradually diminish on larger and larger scales. Also, the deviations are time-dependent, i.e. they become larger and larger with increasing cosmic time. The most emphasized result is that the spatial deviations between baryons and dark matter revealed by velocity field are more significant than that by density field. At z = 0, at the $1{{\ \rm per\ cent}}$ level of deviation, the deviation scale is about $3.7\, {h^{-1} {\rm Mpc}}$ for density field, while as large as $23\, {h^{-1} {\rm Mpc}}$ for velocity field, a scale that falls within the weakly non-linear regime for the structure formation paradigm. Our results indicate that the effect of turbulence heating is indeed comparable to that of these processes such as SN and AGN feedback.

Possible formation of ring galaxies by torus-shaped magnetic wormholes

We present the hypothesis that some of ring galaxies were formed by relic magnetic torus-shaped wormholes. In the primordial plasma before the recombination magnetic fields of wormholes trap baryons whose energy is smaller than a threshold energy. They work as the Maxwell’s demons collecting baryons from the nearest (horizon size) region and thus forming clumps of baryonic matter which have the same torus-like shapes as wormhole throats. Such clumps may serve as seeds for the formation of ring galaxies and smaller objects having the ring form. Upon the recombination torus-like clumps may decay and merge. Unlike galaxies, such objects may contain less or even no dark matter in halos. However the most stringent feature of such objects is the presence of a large-scale toroidal magnetic field. We show that there are threshold values of magnetic fields which give the upper and lower boundary values for the baryon clumps in such protogalaxies.

The continuum spectrum of hypernuclear trios

The spectrum of hypernuclear trios composed of a Λ baryon and two nucleons is the subject of an ongoing experimental campaign, aiming to study the interaction of the Λ particle with a neutron, and the 3-body Λ-nucleon-nucleon force. In this manuscript we utilize baryonic effective field theory at leading order, constrained to reproduce the available low energy light hypernuclear data, to study the continuum spectrum of such hypernuclear trios. Using the complex scaling method and the inverse analytic continuation in the coupling constant method we find the existence of a virtual state in the ΛnpJπ=3/2+ channel, leading to cross-section enhancement near threshold. For the ΛnnJπ=1/2+ channel we predict a resonance state. Depending, however, on the value of the ΛN scattering length, the resonance pole moves from the physical to the unphysical complex energy sheet within the experimental bounds.

Constraints from a large- Nc analysis on meson-baryon interactions at chiral order Q3

We consider the chiral Lagrangian for baryon fields with J^P =\frac{1}{2}^+ or J^P =\frac{3}{2}^+ quantum numbers as constructed from QCD with up, down and strange quarks. The specific class of counter terms that are of chiral order Q^3 and contribute to meson-baryon interactions at the two-body level is constructed. Altogether we find 24 terms. In order to pave the way for realistic applications we establish a set of 22 sum rules for the low-energy constants as they are implied by QCD in the large-N_c limit. Given such a constraint there remain only 2 independent unknown parameters that need to be determined by either Lattice QCD simulations or directly from experimental cross section measurements. At subleading order we arrive at 5 parameters.

Dark matter as scalaron in f(R) gravity models

We explore the scalar field obtained under the conformal transformation of the spacetime metric gμν from the Jordan frame to the Einstein frame in f(R) gravity. This scalar field is the result of the modification in the gravitational part of the Einstein's general relativistic theory of gravity. For f(R)=R1+δ/Rcδ, we find the effective potential of the scalar field and calculate the mass of the scalar field particle “scalaron”. It is shown that the mass of the scalaron depends upon the energy density of standard matter in the background (in solar system, mϕ∼ 10−16 eV) . The interaction between standard matter and scalaron is weak in the high curvature regime. This linkage between the mass of the scalaron and the background leads to the physical effects of dark matter and is expected to reflect the anisotropic propagation of scalaron in moving baryonic matter fields as in merging clusters (Bullet cluster, the Abell 520 system, MACS etc.). Such scenario also satisfies the local gravity constraints of f(R) gravity. We further calculate the equation of state of the scalar field in the action-angle variable formalism and show its distinct features as the dark matter and dark energy with respect to energy density of the scalar field at different values of the model parameter δ.

Dark matter as scalaron in f(R) gravity models

We explore the scalar field obtained under the conformal transformation of the spacetime metric $g_{\mu\nu}$ from the Jordan frame to the Einstein frame in $f(R)$ gravity. This scalar field is the result of the modification in the gravitational part of the Einstein's general relativistic theory of gravity. For $f(R)=\frac{R^{1+\delta}}{R_{c}^{\delta}}$, we find the effective potential of the scalar field and calculate the mass of the scalar field particle scalaron. It is shown that the mass of the scalaron depends upon the energy density of standard matter in the background. The interaction between standard matter and scalaron is weak in the high curvature regime. This linkage between the mass of the scalaron and the background leads to the physical effects of dark matter and is expected to reflect the anisotropic propagation of scalaron in moving baryonic matter fields as in merging clusters (Bullet cluster, the Abell 520 system, MACS etc.). Such scenario also satisfies the local gravity constraints of $f(R)$ gravity. We further calculate the equation of state of the scalar field in the action-angle variable formalism and show its distinct features as the dark matter and dark energy with respect to energy density of the scalar field at different values of the model parameter $\delta$.

Starburst and post-starburst high-redshift protogalaxies

Quenching of star-formation has been identified in many starburst and post-starburst galaxies, indicating burst-like star-formation histories (SFH) in the primordial Universe. Galaxies undergoing violent episodes of star-formation are expected to be rich in high energy cosmic rays (CRs). We have investigated the role of these CRs in such environments, particularly how they could contribute to this burst-like SFH via quenching and feedback. These high energy particles interact with the baryon and radiation fields of their host via hadronic processes to produce secondary leptons. The secondary particles then also interact with ambient radiation fields to generate X-rays through inverse-Compton scattering. In addition, they can thermalise directly with the semi-ionised medium via Coulomb processes. Heating at a rate of ∼10−25 erg cm−3 s−1can be attained by Coulomb processes in a star-forming galaxy with one core-collapse SN event per decade, and this is sufficient to cause quenching of star-formation. At high-redshift, a substantial amount of CR secondary electron energy can be diverted into inverse-Compton X-ray emission. This yields an X-ray luminosity of above 1041 erg s−1by redshiftz = 7 which drives a further heating effect, operating over larger scales. This would be able to halt inflowing cold gas filaments, strangulating subsequent star-formation. We selected a sample of 16 starburst and post-starburst galaxies at 7 ≲ z ≲ 9 and determine the star-formation rates they could have sustained. We applied a model with CR injection, propagation and heating to calculate energy deposition rates in these 16 sources. Our calculations show that CR feedback cannot be neglected as it has the strength to suppress star-formation in these systems. We also show that their currently observed quiescence is consistent with the suffocation of cold inflows, probably by a combination of X-ray and CR heating.

Spontaneous and gravitational baryogenesis

Some problems of spontaneous and gravitational baryogenesis are discussed. Gravity modification due to the curvature-dependent term in gravitational baryogenesis scenario is considered. It is shown that the interaction of baryonic fields with the curvature scalar leads to strong instability of the gravitational equations of motion and as a result to noticeable distortion of the standard cosmology.

Framework for the chiral extrapolation of the charmed baryon ground-state masses

We consider the chiral Lagrangian for charmed baryon fields with $J^P =\frac{1}{2}^+$ or $J^P =\frac{3}{2}^+$ quantum numbers. A chiral expansion framework for the baryon ground state masses is worked out to N$^3$LO as to compute their dependence on the up, down and strange quark masses for finite box QCD lattice simulations. It is formulated in terms of on-shell meson and baryon masses. The convergence of such a scheme is illustrated with physical masses as taken from the PDG. The counter terms relevant at N$^3$LO are correlated systematically by large-$N_c$ sum rules to leading and subleading order in a manner that keeps the renormalization scale invariance of the approach.