Jessie de Kruijf, Eleonora Vanzan, Kimberly K. Boddy, Alvise Raccanelli, Nicola Bartolo
The primordial power spectrum of curvature perturbations has been well-measured on large scales but remains fairly unconstrained at smaller scales, where significant deviations from $Lambda$CDM may occur. Measurements of 21-cm intensity mapping in the dark ages promise to access very small scales that have yet to be probed, extending beyond the reach of CMB and galaxy surveys. In this paper, we investigate how small-scale power-law enhancements -- or blue tilts -- of the primordial power spectrum affect the 21-cm power spectrum. We consider generic enhancements due to curvature modes, isocurvature modes, and runnings of the spectral tilt. We present forecasts for Earth- and lunar-based instruments to detect a blue-tilted primordial spectrum. We find that an Earth-based instrument capable of reaching the dark ages could detect any enhancements of power on nearly all the scales it can observe, which depends on the baseline of the interferometer. The smallest scales observed by such an instrument can only detect a very strong enhancement. However, an instrument on the far side of the Moon of the same size would be able to probe shallower slopes with higher precision. We forecast results for instruments with $100 , {rm km} , (3000 , {rm km})$ baselines and find that they can probe up to scales of order $k_{rm max} sim 8 , {rm Mpc}^{-1} , (k_{rm max} sim 250 , {rm Mpc}^{-1})$, thereby providing invaluable information on exotic physics and testing inflationary models on scales not otherwise accessible.
{"title":"Searching for blue in the dark","authors":"Jessie de Kruijf, Eleonora Vanzan, Kimberly K. Boddy, Alvise Raccanelli, Nicola Bartolo","doi":"arxiv-2408.04991","DOIUrl":"https://doi.org/arxiv-2408.04991","url":null,"abstract":"The primordial power spectrum of curvature perturbations has been\u0000well-measured on large scales but remains fairly unconstrained at smaller\u0000scales, where significant deviations from $Lambda$CDM may occur. Measurements\u0000of 21-cm intensity mapping in the dark ages promise to access very small scales\u0000that have yet to be probed, extending beyond the reach of CMB and galaxy\u0000surveys. In this paper, we investigate how small-scale power-law enhancements\u0000-- or blue tilts -- of the primordial power spectrum affect the 21-cm power\u0000spectrum. We consider generic enhancements due to curvature modes, isocurvature\u0000modes, and runnings of the spectral tilt. We present forecasts for Earth- and\u0000lunar-based instruments to detect a blue-tilted primordial spectrum. We find\u0000that an Earth-based instrument capable of reaching the dark ages could detect\u0000any enhancements of power on nearly all the scales it can observe, which\u0000depends on the baseline of the interferometer. The smallest scales observed by\u0000such an instrument can only detect a very strong enhancement. However, an\u0000instrument on the far side of the Moon of the same size would be able to probe\u0000shallower slopes with higher precision. We forecast results for instruments\u0000with $100 , {rm km} , (3000 , {rm km})$ baselines and find that they can\u0000probe up to scales of order $k_{rm max} sim 8 , {rm Mpc}^{-1} , (k_{rm\u0000max} sim 250 , {rm Mpc}^{-1})$, thereby providing invaluable information on\u0000exotic physics and testing inflationary models on scales not otherwise\u0000accessible.","PeriodicalId":501207,"journal":{"name":"arXiv - PHYS - Cosmology and Nongalactic Astrophysics","volume":"192 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141934238","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We study the effect of gravitational clustering at small scales on larger scales by studying mode coupling between virialised halos. We build on the calculation by Peebles (1974) where it was shown that a virialised halo does not contribute any mode coupling terms at small wave numbers $k$. Using a perturbative expansion in wave number, we show that this effect is small and arises from the deviation of halo shapes from spherical and also on tidal interactions between halos. We connect this with the impact of finite mass resolution of cosmological N-Body simulations on the evolution of perturbations at early times. This difference between the expected evolution and the evolution obtained in cosmological N-Body simulations can be quantified using such an estimate. We also explore the impact of a finite shortest scale up to which the desired power spectrum is realised in simulations. Several simulation studies have shown that this effect is small in comparison with the effect of perturbations at large scales on smaller scales. It is nevertheless important to study these effects and develop a general approach for estimating their magnitude. This is especially relevant in the present era of precision cosmology. We provide basic estimates of the magnitude of these effects and their power spectrum dependence. We find that the impact of small scale cutoff in the initial power spectrum and discreteness increases with $(n+3)$, with $n$ being the index of the power spectrum. In general, we recommend that cosmological simulation data should be used only if the scale of non-linearity, defined as the scale where the linearly extrapolated {it rms} amplitude of fluctuations is unity, is larger than the average inter-particle separation.
{"title":"On the origin of transient features in cosmological N-Body Simulations","authors":"J. S. Bagla, Swati Gavas","doi":"arxiv-2408.05118","DOIUrl":"https://doi.org/arxiv-2408.05118","url":null,"abstract":"We study the effect of gravitational clustering at small scales on larger\u0000scales by studying mode coupling between virialised halos. We build on the\u0000calculation by Peebles (1974) where it was shown that a virialised halo does\u0000not contribute any mode coupling terms at small wave numbers $k$. Using a\u0000perturbative expansion in wave number, we show that this effect is small and\u0000arises from the deviation of halo shapes from spherical and also on tidal\u0000interactions between halos. We connect this with the impact of finite mass\u0000resolution of cosmological N-Body simulations on the evolution of perturbations\u0000at early times. This difference between the expected evolution and the\u0000evolution obtained in cosmological N-Body simulations can be quantified using\u0000such an estimate. We also explore the impact of a finite shortest scale up to\u0000which the desired power spectrum is realised in simulations. Several simulation\u0000studies have shown that this effect is small in comparison with the effect of\u0000perturbations at large scales on smaller scales. It is nevertheless important\u0000to study these effects and develop a general approach for estimating their\u0000magnitude. This is especially relevant in the present era of precision\u0000cosmology. We provide basic estimates of the magnitude of these effects and\u0000their power spectrum dependence. We find that the impact of small scale cutoff\u0000in the initial power spectrum and discreteness increases with $(n+3)$, with $n$\u0000being the index of the power spectrum. In general, we recommend that\u0000cosmological simulation data should be used only if the scale of non-linearity,\u0000defined as the scale where the linearly extrapolated {it rms} amplitude of\u0000fluctuations is unity, is larger than the average inter-particle separation.","PeriodicalId":501207,"journal":{"name":"arXiv - PHYS - Cosmology and Nongalactic Astrophysics","volume":"20 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141934310","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The uncertainties in photometric redshifts and stellar masses from imaging surveys affect galaxy sample selection, their abundance measurements, as well as the measured weak lensing signals. We develop a framework to assess the systematic effects arising from the use of redshifts and stellar masses derived from photometric data, and explore their impact on the inferred galaxy-dark matter connection. We use galaxy catalogues from the UniverseMachine (UM) galaxy formation model to create Pz-mock galaxy samples that approximately follow the redshift errors in the Subaru HSC survey. We focus on galaxy stellar-mass thresholds ranging from $logleft[M_*/(h^{-2}M_odot)right]$ from $8.6$ to $11.2$ in steps of 0.2 dex within two redshift bins $0.30-0.55$ and $0.55-0.80$. A comparison of the Pz-mock samples to true galaxy samples in UM shows a relatively mild sample contamination for thresholds with $logleft[M_{*,rm limit}/(h^{-2}M_odot)right]<10.6$, while an increasing contamination towards the more massive end. We show how such contamination affects the measured abundance and the lensing signal. A joint HOD modelling of the observables from the Pz-mock compared to the truth in the UM informs the systematic biases on the average halo masses of central galaxies in the HSC survey. Even with a reasonably conservative choice of photo-$z$ errors in Pz-mock, we show that the inferred halo masses deduced from the HSC galaxies for low-mass thresholds will have a systematic bias smaller than 0.05 dex. Beyond $logleft[M_{*,rm limit}/(h^{-2}M_odot)right]=10.6$, the inferred halo masses show an increasing systematic bias with stellar mass, reaching values of order $0.2$ dex, larger than the statistical error.
{"title":"Galaxy-dark matter connection from weak lensing in imaging surveys: Impact of photometric redshift errors","authors":"Navin Chaurasiya, Surhud More, Daichi Kashino, Shogo Masaki, Shogo Ishikawa","doi":"arxiv-2408.05013","DOIUrl":"https://doi.org/arxiv-2408.05013","url":null,"abstract":"The uncertainties in photometric redshifts and stellar masses from imaging\u0000surveys affect galaxy sample selection, their abundance measurements, as well\u0000as the measured weak lensing signals. We develop a framework to assess the\u0000systematic effects arising from the use of redshifts and stellar masses derived\u0000from photometric data, and explore their impact on the inferred galaxy-dark\u0000matter connection. We use galaxy catalogues from the UniverseMachine (UM)\u0000galaxy formation model to create Pz-mock galaxy samples that approximately\u0000follow the redshift errors in the Subaru HSC survey. We focus on galaxy\u0000stellar-mass thresholds ranging from $logleft[M_*/(h^{-2}M_odot)right]$\u0000from $8.6$ to $11.2$ in steps of 0.2 dex within two redshift bins $0.30-0.55$\u0000and $0.55-0.80$. A comparison of the Pz-mock samples to true galaxy samples in\u0000UM shows a relatively mild sample contamination for thresholds with\u0000$logleft[M_{*,rm limit}/(h^{-2}M_odot)right]<10.6$, while an increasing\u0000contamination towards the more massive end. We show how such contamination\u0000affects the measured abundance and the lensing signal. A joint HOD modelling of\u0000the observables from the Pz-mock compared to the truth in the UM informs the\u0000systematic biases on the average halo masses of central galaxies in the HSC\u0000survey. Even with a reasonably conservative choice of photo-$z$ errors in\u0000Pz-mock, we show that the inferred halo masses deduced from the HSC galaxies\u0000for low-mass thresholds will have a systematic bias smaller than 0.05 dex.\u0000Beyond $logleft[M_{*,rm limit}/(h^{-2}M_odot)right]=10.6$, the inferred\u0000halo masses show an increasing systematic bias with stellar mass, reaching\u0000values of order $0.2$ dex, larger than the statistical error.","PeriodicalId":501207,"journal":{"name":"arXiv - PHYS - Cosmology and Nongalactic Astrophysics","volume":"4 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141934243","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jordan Hoffmann, Clancy W. James, Marcin Glowacki, Jason X. Prochaska, Alexa C. Gordon, Adam T. Deller, Ryan M. Shannon, Stuart D. Ryder
Fast radio burst (FRB) science primarily revolves around two facets: the origin of these bursts and their use in cosmological studies. This work follows from previous redshift-dispersion measure ($z$-DM) analyses in which we model instrumental biases and simultaneously fit population parameters and cosmological parameters to the observed population of FRBs. This sheds light on both the progenitors of FRBs and cosmological questions. Previously, we have completed similar analyses with data from the Australian Square Kilometer Array Pathfinder (ASKAP) and the Murriyang (Parkes) Multibeam system. With this manuscript, we additionally incorporate data from the Deep Synoptic Array (DSA) and the Five-hundred-meter Aperture Spherical Telescope (FAST), invoke a Markov chain Monte Carlo (MCMC) sampler and implement uncertainty in the Galactic DM contributions. The latter leads to larger uncertainties in derived model parameters than previous estimates despite the additional data. We provide refined constraints on FRB population parameters and derive a new constraint on the minimum FRB energy of log$,E_{mathrm{min}}$(erg)=39.49$^{+0.39}_{-1.48}$ which is significantly higher than bursts detected from strong repeaters. This result may indicate a low-energy turnover in the luminosity function or may suggest that strong repeaters have a different luminosity function to single bursts. We also predict that FAST will detect 25-41% of their FRBs at $z gtrsim 2$ and DSA will detect 2-12% of their FRBs at $z gtrsim 1$.
{"title":"Modelling DSA, FAST and CRAFT surveys in a z-DM analysis and constraining a minimum FRB energy","authors":"Jordan Hoffmann, Clancy W. James, Marcin Glowacki, Jason X. Prochaska, Alexa C. Gordon, Adam T. Deller, Ryan M. Shannon, Stuart D. Ryder","doi":"arxiv-2408.04878","DOIUrl":"https://doi.org/arxiv-2408.04878","url":null,"abstract":"Fast radio burst (FRB) science primarily revolves around two facets: the\u0000origin of these bursts and their use in cosmological studies. This work follows\u0000from previous redshift-dispersion measure ($z$-DM) analyses in which we model\u0000instrumental biases and simultaneously fit population parameters and\u0000cosmological parameters to the observed population of FRBs. This sheds light on\u0000both the progenitors of FRBs and cosmological questions. Previously, we have\u0000completed similar analyses with data from the Australian Square Kilometer Array\u0000Pathfinder (ASKAP) and the Murriyang (Parkes) Multibeam system. With this\u0000manuscript, we additionally incorporate data from the Deep Synoptic Array (DSA)\u0000and the Five-hundred-meter Aperture Spherical Telescope (FAST), invoke a Markov\u0000chain Monte Carlo (MCMC) sampler and implement uncertainty in the Galactic DM\u0000contributions. The latter leads to larger uncertainties in derived model\u0000parameters than previous estimates despite the additional data. We provide\u0000refined constraints on FRB population parameters and derive a new constraint on\u0000the minimum FRB energy of log$,E_{mathrm{min}}$(erg)=39.49$^{+0.39}_{-1.48}$\u0000which is significantly higher than bursts detected from strong repeaters. This\u0000result may indicate a low-energy turnover in the luminosity function or may\u0000suggest that strong repeaters have a different luminosity function to single\u0000bursts. We also predict that FAST will detect 25-41% of their FRBs at $z\u0000gtrsim 2$ and DSA will detect 2-12% of their FRBs at $z gtrsim 1$.","PeriodicalId":501207,"journal":{"name":"arXiv - PHYS - Cosmology and Nongalactic Astrophysics","volume":"55 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141934239","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Luis A. Escamilla, Donatella Fiorucci, Giovanni Montani, Eleonora Di Valentino
We investigate a modified cosmological model aimed at addressing the Hubble tension, considering revised dynamics in the late Universe. The model introduces a parameter $c$ affecting the evolution equations, motivated by a modified Poisson algebra inspired by effective Loop Quantum Cosmology. Our analysis includes diverse background datasets such as Cosmic Chronometers, Pantheon+ Type Ia Supernovae (with and without the SH0ES calibration), SDSS, DESY6 and DESI Baryon Acoustic Oscillations, and background information of the Cosmic Microwave Background. We find that the model alleviates the Hubble tension in most of the dataset combinations, with cases reducing discrepancies to below $1sigma$ when including SH0ES. However, the model exhibits minimal improvement in the overall fit when compared to $Lambda$CDM, and Bayesian evidence generally favors the standard model. Theoretical foundations support this approach as a subtle adjustment to low-redshift dynamics, suggesting potential for further exploration into extensions of $Lambda$CDM. Despite challenges in data fitting, our findings underscore the promise of small-scale modifications in reconciling cosmological tensions.
{"title":"Exploring the Hubble tension with a late time Modified Gravity scenario","authors":"Luis A. Escamilla, Donatella Fiorucci, Giovanni Montani, Eleonora Di Valentino","doi":"arxiv-2408.04354","DOIUrl":"https://doi.org/arxiv-2408.04354","url":null,"abstract":"We investigate a modified cosmological model aimed at addressing the Hubble\u0000tension, considering revised dynamics in the late Universe. The model\u0000introduces a parameter $c$ affecting the evolution equations, motivated by a\u0000modified Poisson algebra inspired by effective Loop Quantum Cosmology. Our\u0000analysis includes diverse background datasets such as Cosmic Chronometers,\u0000Pantheon+ Type Ia Supernovae (with and without the SH0ES calibration), SDSS,\u0000DESY6 and DESI Baryon Acoustic Oscillations, and background information of the\u0000Cosmic Microwave Background. We find that the model alleviates the Hubble\u0000tension in most of the dataset combinations, with cases reducing discrepancies\u0000to below $1sigma$ when including SH0ES. However, the model exhibits minimal\u0000improvement in the overall fit when compared to $Lambda$CDM, and Bayesian\u0000evidence generally favors the standard model. Theoretical foundations support\u0000this approach as a subtle adjustment to low-redshift dynamics, suggesting\u0000potential for further exploration into extensions of $Lambda$CDM. Despite\u0000challenges in data fitting, our findings underscore the promise of small-scale\u0000modifications in reconciling cosmological tensions.","PeriodicalId":501207,"journal":{"name":"arXiv - PHYS - Cosmology and Nongalactic Astrophysics","volume":"6 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141934244","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The morphology and the characteristic scale of polarized structures provide crucial insights into the mechanisms that drives turbulence and maintains magnetic fields in magneto-ionic plasma. We aim to establish the efficacy of Minkowski functionals as quantitative statistical probes of filamentary morphology of polarized synchrotron emission resulting from fluctuation dynamo action. Using synthetic observations generated from magnetohydrodynamic simulations of fluctuation dynamos with varying driving scales ($ell_{rm f}$) of turbulence in isothermal, incompressible, and subsonic media, we study the relation between different morphological measures, and their connection to fractional polarization ($p_{rm f}$). We find that Faraday depolarization at low frequencies give rise to small-scale polarized structures that have higher filamentarity as compared to the intrinsic structures that are comparable to $ell_{rm f}$. Above $sim3,{rm GHz}$, the number of connected polarized structures per unit area ($N_{rm CC, peak}$) is related to the mean $p_{rm f}$ ($langle p_{rm f} rangle$) of the emitting region as $langle p_{rm f} rangle propto N_{rm CC, peak}^{-1/4}$, provided the scale of the detectable emitting region is larger than $ell_{rm f}$. This implies that $N_{rm CC,peak}$ represents the number of turbulent cells projected on the plane of the sky and can be directly used to infer $ell_{rm f}$ via the relation $ell_{rm f} propto N_{rm CC,peak}^{-1/2}$. An estimate on $ell_{rm f}$ thus directly allows for pinning down the turbulence driving mechanism in astrophysical systems. While the simulated conditions are mostly prevalent in the intracluster medium of galaxy clusters, the qualitative morphological features are also applicable in the context of interstellar medium in galaxies.
{"title":"Probing the morphology of polarized emission induced by fluctuation dynamo using Minkowski functionals","authors":"Riju Dutta, Sharanya Sur, Aritra Basu","doi":"arxiv-2408.04581","DOIUrl":"https://doi.org/arxiv-2408.04581","url":null,"abstract":"The morphology and the characteristic scale of polarized structures provide\u0000crucial insights into the mechanisms that drives turbulence and maintains\u0000magnetic fields in magneto-ionic plasma. We aim to establish the efficacy of\u0000Minkowski functionals as quantitative statistical probes of filamentary\u0000morphology of polarized synchrotron emission resulting from fluctuation dynamo\u0000action. Using synthetic observations generated from magnetohydrodynamic\u0000simulations of fluctuation dynamos with varying driving scales ($ell_{rm f}$)\u0000of turbulence in isothermal, incompressible, and subsonic media, we study the\u0000relation between different morphological measures, and their connection to\u0000fractional polarization ($p_{rm f}$). We find that Faraday depolarization at\u0000low frequencies give rise to small-scale polarized structures that have higher\u0000filamentarity as compared to the intrinsic structures that are comparable to\u0000$ell_{rm f}$. Above $sim3,{rm GHz}$, the number of connected polarized\u0000structures per unit area ($N_{rm CC, peak}$) is related to the mean $p_{rm\u0000f}$ ($langle p_{rm f} rangle$) of the emitting region as $langle p_{rm f}\u0000rangle propto N_{rm CC, peak}^{-1/4}$, provided the scale of the detectable\u0000emitting region is larger than $ell_{rm f}$. This implies that $N_{rm\u0000CC,peak}$ represents the number of turbulent cells projected on the plane of\u0000the sky and can be directly used to infer $ell_{rm f}$ via the relation\u0000$ell_{rm f} propto N_{rm CC,peak}^{-1/2}$. An estimate on $ell_{rm f}$\u0000thus directly allows for pinning down the turbulence driving mechanism in\u0000astrophysical systems. While the simulated conditions are mostly prevalent in\u0000the intracluster medium of galaxy clusters, the qualitative morphological\u0000features are also applicable in the context of interstellar medium in galaxies.","PeriodicalId":501207,"journal":{"name":"arXiv - PHYS - Cosmology and Nongalactic Astrophysics","volume":"38 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141934245","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this work, we investigate whether the baryon acoustic oscillation (BAO) measurements from redshift surveys, like the Sloan Digital Sky Survey (SDSS), and the Dark Energy Spectroscopic Instrument (DESI), are consistent with each other. We do so by obtaining the Hubble and deceleration parameter, respectively $H(z)$ and $q(z)$, from both datasets using a non-parametric reconstruction, so that our results do not depend on any {it a priori} assumptions about the underlying cosmological model. We find that the reconstructed $H(z)$ and $q(z)$ from SDSS are significantly inconsistent with those obtained from DESI, and that both are only marginally consistent with the $Lambda$CDM model ($sim 3sigma$ confidence level). Interestingly, the combined SDSS and DESI dataset reconciles with the standard model. These results are mostly unchanged with respect to different assumptions on the sound horizon scale value, as well as different reconstruction kernels. We also verify the results for the null diagnostic $mathcal{O}_{rm m}(z)$, finding that SDSS favours a quintessence-like dark energy model, whereas a phantom-like dark energy is preferred by DESI data, and once again the combined dataset strongly agrees with $Lambda$CDM. Therefore, our results call the attention for further examination of such inconsistency, as they can lead to biased and divergent results regarding the validity of the standard model, or the suggestion of new physics.
{"title":"Consistency tests between SDSS and DESI BAO measurements","authors":"Basundhara Ghosh, Carlos Bengaly","doi":"arxiv-2408.04432","DOIUrl":"https://doi.org/arxiv-2408.04432","url":null,"abstract":"In this work, we investigate whether the baryon acoustic oscillation (BAO)\u0000measurements from redshift surveys, like the Sloan Digital Sky Survey (SDSS),\u0000and the Dark Energy Spectroscopic Instrument (DESI), are consistent with each\u0000other. We do so by obtaining the Hubble and deceleration parameter,\u0000respectively $H(z)$ and $q(z)$, from both datasets using a non-parametric\u0000reconstruction, so that our results do not depend on any {it a priori}\u0000assumptions about the underlying cosmological model. We find that the\u0000reconstructed $H(z)$ and $q(z)$ from SDSS are significantly inconsistent with\u0000those obtained from DESI, and that both are only marginally consistent with the\u0000$Lambda$CDM model ($sim 3sigma$ confidence level). Interestingly, the\u0000combined SDSS and DESI dataset reconciles with the standard model. These\u0000results are mostly unchanged with respect to different assumptions on the sound\u0000horizon scale value, as well as different reconstruction kernels. We also\u0000verify the results for the null diagnostic $mathcal{O}_{rm m}(z)$, finding\u0000that SDSS favours a quintessence-like dark energy model, whereas a phantom-like\u0000dark energy is preferred by DESI data, and once again the combined dataset\u0000strongly agrees with $Lambda$CDM. Therefore, our results call the attention\u0000for further examination of such inconsistency, as they can lead to biased and\u0000divergent results regarding the validity of the standard model, or the\u0000suggestion of new physics.","PeriodicalId":501207,"journal":{"name":"arXiv - PHYS - Cosmology and Nongalactic Astrophysics","volume":"56 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141934335","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Recent studies suggest that cold dark matter subhalos are hard to disrupt and almost all cases of subhalo disruption observed in numerical simulations are due to numerical effects. However, these findings primarily relied on idealized numerical experiments, which do not fully capture the realistic conditions of subhalo evolution within a hierarchical cosmological context. Based on the Aquarius simulations, we identify clear segregation in the population of surviving and disrupted subhalos, which corresponds to two distinct acquisition channels of subhalos. We find that all of the first-order subhalos accreted after redshift 2 survive to the present time without suffering from artificial disruption. On the other hand, most of the disrupted subhalos are sub-subhalos accreted at high redshift. Unlike the first-order subhalos, sub-subhalos experience pre-processing and many of them are accreted through major mergers at high redshift, resulting in very high mass loss rates. We confirm these high mass loss rates are physical through both numerical experiments and semi-analytical modeling, thus supporting a physical origin for their rapid disappearance in the simulation. Even though we cannot verify whether these subhalos have fully disrupted or not, their extreme mass loss rates dictate that they can at most contribute a negligible fraction to the very low mass end of the subhalo mass function. We thus conclude that current state-of-the-art cosmological simulations have reliably resolved the subhalo population.
{"title":"Why artificial disruption is not a concern for current cosmological simulations","authors":"Feihong He, Jiaxin Han, Zhaozhou Li","doi":"arxiv-2408.04470","DOIUrl":"https://doi.org/arxiv-2408.04470","url":null,"abstract":"Recent studies suggest that cold dark matter subhalos are hard to disrupt and\u0000almost all cases of subhalo disruption observed in numerical simulations are\u0000due to numerical effects. However, these findings primarily relied on idealized\u0000numerical experiments, which do not fully capture the realistic conditions of\u0000subhalo evolution within a hierarchical cosmological context. Based on the\u0000Aquarius simulations, we identify clear segregation in the population of\u0000surviving and disrupted subhalos, which corresponds to two distinct acquisition\u0000channels of subhalos. We find that all of the first-order subhalos accreted\u0000after redshift 2 survive to the present time without suffering from artificial\u0000disruption. On the other hand, most of the disrupted subhalos are sub-subhalos\u0000accreted at high redshift. Unlike the first-order subhalos, sub-subhalos\u0000experience pre-processing and many of them are accreted through major mergers\u0000at high redshift, resulting in very high mass loss rates. We confirm these high\u0000mass loss rates are physical through both numerical experiments and\u0000semi-analytical modeling, thus supporting a physical origin for their rapid\u0000disappearance in the simulation. Even though we cannot verify whether these\u0000subhalos have fully disrupted or not, their extreme mass loss rates dictate\u0000that they can at most contribute a negligible fraction to the very low mass end\u0000of the subhalo mass function. We thus conclude that current state-of-the-art\u0000cosmological simulations have reliably resolved the subhalo population.","PeriodicalId":501207,"journal":{"name":"arXiv - PHYS - Cosmology and Nongalactic Astrophysics","volume":"13 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141934334","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yerlan Myrzakulov, O. Donmez, M. Koussour, D. Alizhanov, S. Bekchanov, J. Rayimbaev
In this study, we examined the late-time cosmic expansion of the universe within the framework of $f(Q, L_m)$ gravity, where $Q$ denotes the non-metricity and $L_{m}$ represents the matter Lagrangian. We analyzed a linear $f(Q, L_m)$ model of the form $f(Q, L_m) = -alpha Q + 2 L_{m} + beta$. Using MCMC methods, we constrained the model parameters $H_0$, $alpha$, and $beta$ with various datasets, including $H(z)$, Pantheon+SH0ES, and BAO data. For the $H(z)$ dataset, we found $H_0 = 67.90 pm 0.66$, $alpha = 0.1072_{-0.0069}^{+0.0054}$, and $beta = -1988.2 pm 1.0$. For the Pantheon+SH0ES dataset, $H_0 = 70.05 pm 0.68$, $alpha = 0.0916_{-0.0033}^{+0.0028}$, and $beta = -1988.3 pm 1.0$. For the BAO dataset, $H_0 = 68.1 pm 1.0$, $alpha = 0.1029_{-0.0052}^{+0.0041}$, and $beta = -1988.24 pm 0.99$. Moreover, the energy density remains positive and approaches zero in the distant future, and the deceleration parameter indicates a transition from deceleration to acceleration, with transition redshifts of $z_t = 0.60$, $z_t = 0.78$, and $z_t = 0.66$ for the respective datasets. These findings align with previous observational studies and contribute to our understanding of the universe's expansion dynamics.
{"title":"Late-time cosmology in $f(Q, L_m)$ gravity: Analytical solutions and observational fits","authors":"Yerlan Myrzakulov, O. Donmez, M. Koussour, D. Alizhanov, S. Bekchanov, J. Rayimbaev","doi":"arxiv-2408.04770","DOIUrl":"https://doi.org/arxiv-2408.04770","url":null,"abstract":"In this study, we examined the late-time cosmic expansion of the universe\u0000within the framework of $f(Q, L_m)$ gravity, where $Q$ denotes the\u0000non-metricity and $L_{m}$ represents the matter Lagrangian. We analyzed a\u0000linear $f(Q, L_m)$ model of the form $f(Q, L_m) = -alpha Q + 2 L_{m} + beta$.\u0000Using MCMC methods, we constrained the model parameters $H_0$, $alpha$, and\u0000$beta$ with various datasets, including $H(z)$, Pantheon+SH0ES, and BAO data.\u0000For the $H(z)$ dataset, we found $H_0 = 67.90 pm 0.66$, $alpha =\u00000.1072_{-0.0069}^{+0.0054}$, and $beta = -1988.2 pm 1.0$. For the\u0000Pantheon+SH0ES dataset, $H_0 = 70.05 pm 0.68$, $alpha =\u00000.0916_{-0.0033}^{+0.0028}$, and $beta = -1988.3 pm 1.0$. For the BAO\u0000dataset, $H_0 = 68.1 pm 1.0$, $alpha = 0.1029_{-0.0052}^{+0.0041}$, and\u0000$beta = -1988.24 pm 0.99$. Moreover, the energy density remains positive and\u0000approaches zero in the distant future, and the deceleration parameter indicates\u0000a transition from deceleration to acceleration, with transition redshifts of\u0000$z_t = 0.60$, $z_t = 0.78$, and $z_t = 0.66$ for the respective datasets. These\u0000findings align with previous observational studies and contribute to our\u0000understanding of the universe's expansion dynamics.","PeriodicalId":501207,"journal":{"name":"arXiv - PHYS - Cosmology and Nongalactic Astrophysics","volume":"47 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141934241","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
MohammadHossein Jamshidi, Abdolali Banihashemi, Nima Khosravi
We have studied the cosmic microwave background (CMB) map looking for features beyond cosmological isotropy. We began by tiling the CMB variance map (which are produced by different smoothing scales) with stripes of different sizes along the most prominent dipole direction. We were able to confirm previous findings regarding the significance of the dipole. Furthermore, we discovered that some of the higher multipoles exhibit significance comparable to the dipole which naturally depends on the smoothing scales. At the end, we discussed this result having an eye on look-elsewhere-effect. We believe our results may indicate an anomalous patch in the CMB sky that warrants further investigation.
{"title":"On the (higher multipoles) variance asymmetry in the cosmic microwave background","authors":"MohammadHossein Jamshidi, Abdolali Banihashemi, Nima Khosravi","doi":"arxiv-2408.04712","DOIUrl":"https://doi.org/arxiv-2408.04712","url":null,"abstract":"We have studied the cosmic microwave background (CMB) map looking for\u0000features beyond cosmological isotropy. We began by tiling the CMB variance map\u0000(which are produced by different smoothing scales) with stripes of different\u0000sizes along the most prominent dipole direction. We were able to confirm\u0000previous findings regarding the significance of the dipole. Furthermore, we\u0000discovered that some of the higher multipoles exhibit significance comparable\u0000to the dipole which naturally depends on the smoothing scales. At the end, we\u0000discussed this result having an eye on look-elsewhere-effect. We believe our\u0000results may indicate an anomalous patch in the CMB sky that warrants further\u0000investigation.","PeriodicalId":501207,"journal":{"name":"arXiv - PHYS - Cosmology and Nongalactic Astrophysics","volume":"75 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141934242","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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