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Generalized Distributions of Host Dispersion Measures in the Fast Radio Burst Cosmology
Authors:
Jing-Yi Jia,
Da-Chun Qiang,
Lin-Yu Li,
Hao Wei
Abstract:
As is well known, Hubble tension is one of the most serious challenges in cosmology to date. So, it is of interest to measure the Hubble constant by using some new probes independent of cosmic microwave background (CMB) and type Ia supernovae (SNIa). One of the promising probes is the fast radio bursts (FRBs), which could be useful in cosmology. In the literature, the methodology proposed by Macqu…
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As is well known, Hubble tension is one of the most serious challenges in cosmology to date. So, it is of interest to measure the Hubble constant by using some new probes independent of cosmic microwave background (CMB) and type Ia supernovae (SNIa). One of the promising probes is the fast radio bursts (FRBs), which could be useful in cosmology. In the literature, the methodology proposed by Macquart {\it et al.} has been widely used, in which both $\rm DM_{IGM}$ and $\rm DM_{host}$ are described by probability distribution functions. Recently, it was found that in order to obtain a Hubble constant $H_0$ consistent with the ones of Planck 2018 and SH0ES by using the current ${\cal O}(100)$ localized FRBs, an unusually large $f_{\rm IGM}$ fairly close to its upper bound $1$ is required, if the narrow prior bounded by $0.5$ for the parameter $F$ in the distribution of $\rm DM_{IGM}$ was used. In fact, a small $F$ is the key to make $H_0$ larger. In the present work, we consider a loose prior for the parameter $F$, and find an unusually low $H_0$ by using 125 localized FRBs. We show that the model with loose $F$ prior is strongly preferred over the one with narrow $F$ prior in all terms of the Bayesian evidence and the information criteria AIC, BIC. So, the great Hubble tension between FRBs, Planck 2018 and SH0ES should be taken seriously. Instead of modifying $σ_Δ=Fz^{-0.5}$ in the distribution of $\rm DM_{IGM}$, here we try to find a new way out by generalizing the distribution of $\rm DM_{host}$ with varying location and scale parameters $\ell$ and $e^μ$, respectively. We find that $H_0$ can be consistent with the ones of Planck 2018 and SH0ES in all cases. All the Bayesian evidence and the information criteria AIC, BIC for the generalized distributions of $\rm DM_{host}$ are overwhelmingly strong.
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Submitted 10 October, 2025;
originally announced October 2025.
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The impact of 2D and 3D BAO measurements on the Cosmic Distance Duality Relation with HII galaxies
Authors:
Jie Zheng,
Da-Chun Qiang,
Zhi-Qiang You,
Darshan Kumar
Abstract:
The cosmic distance duality relation (CDDR) is a fundamental and practical condition in observational cosmology that connects the luminosity distance and angular diameter distance. Testing its validity offers a powerful tool to probe new physics beyond the standard cosmological model. In this work, for the first time, we present a novel consistency test of CDDR by combining HII galaxy data with a…
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The cosmic distance duality relation (CDDR) is a fundamental and practical condition in observational cosmology that connects the luminosity distance and angular diameter distance. Testing its validity offers a powerful tool to probe new physics beyond the standard cosmological model. In this work, for the first time, we present a novel consistency test of CDDR by combining HII galaxy data with a comprehensive set of Baryon Acoustic Oscillations (BAO) measurements. The BAO measurements include two-dimensional (2D) BAO and three-dimensional (3D) BAO from the Sloan Digital Sky Survey (SDSS), as well as the latest 3D BAO data from the Dark Energy Spectroscopic Instrument (DESI) Data Release 2 (DR2). We adopt four different parameterizations of the distance duality relation parameter, $η(z)$, to investigate possible deviations and their evolution with cosmic time. To ensure accurate redshift matching across datasets, we reconstruct the distance measures through a model-independent Artificial Neural Network (ANN) approach. {We find no significant deviation from the CDDR (less than 68% confidence level) among four parameterizations. Furthermore, our results show that the constraints on $η(z)$ obtained separately from 2D and 3D BAO measurements are consistent at the 68% confidence level. This indicates that there is no significant tension between the two datasets under the four parameterizations considered. Our ANN reconstruction of HII galaxies could provide constraints on the CDDR at redshifts beyond the reach of Type Ia supernovae.} Finally, the consistency of our results supports the standard CDDR and demonstrates the robustness of our analytical approach.
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Submitted 6 October, 2025; v1 submitted 22 July, 2025;
originally announced July 2025.
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New Insights into Dark Energy from DESI DR2 with CMB and SNIa
Authors:
Da-Chun Qiang,
Jing-Yi Jia,
Hao Wei
Abstract:
Analyses by the Dark Energy Spectroscopic Instrument (DESI) collaboration suggest a significant deviation from the $Λ$CDM model when their baryon acoustic oscillation (BAO) measurements are combined with Planck cosmic microwave background (CMB) data and various Type Ia supernova (SNIa) samples. In this work, we systematically investigate the origin of the deviations from the $Λ$CDM reported in rec…
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Analyses by the Dark Energy Spectroscopic Instrument (DESI) collaboration suggest a significant deviation from the $Λ$CDM model when their baryon acoustic oscillation (BAO) measurements are combined with Planck cosmic microwave background (CMB) data and various Type Ia supernova (SNIa) samples. In this work, we systematically investigate the origin of the deviations from the $Λ$CDM reported in recent cosmological analyses by combining different CMB datasets, BAO measurements, and DESY5 SNIa samples within the $w_0w_a$CDM framework. We find that the DESY5 SNIa sample, particularly its low-redshift component (DES-lowz), the Planck CMB data, the lensing measurements of Planck and ACT-DR6, and the DESI-DR2 BAO measurements contribute most significantly to the observed tensions. In contrast, combinations involving DES-SN, WMAP, SPT, and ACT-DR6 remain consistent with $Λ$CDM within $\sim1σ$. Our results highlight the critical impact of SNIa systematics, CMB data, and the choice of BAO dataset on constraints of dynamical dark energy models. These findings underscore the importance of improved calibration, homogeneity, and cross-validation of observational datasets to robustly assess potential deviations from the standard cosmological model.
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Submitted 14 July, 2025;
originally announced July 2025.
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Alleviating the Hubble Tension with a Local Void and Transitions of the Absolute Magnitude
Authors:
Jing-Yi Jia,
Jia-Lei Niu,
Da-Chun Qiang,
Hao Wei
Abstract:
Nowadays, one of the well-known serious challenges in cosmology is the Hubble tension, namely the discrepancy between the Hubble constants from the local observation of Type Ia supernova (SNIa) and the high-$z$ observation of cosmic microwave background (CMB). Here, we are interested in alleviating the Hubble tension with a local void. The key idea is assuming that we live in a locally underdense…
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Nowadays, one of the well-known serious challenges in cosmology is the Hubble tension, namely the discrepancy between the Hubble constants from the local observation of Type Ia supernova (SNIa) and the high-$z$ observation of cosmic microwave background (CMB). Here, we are interested in alleviating the Hubble tension with a local void. The key idea is assuming that we live in a locally underdense void, where one will feel a faster expansion rate compared to the cosmic average. In the literature, it was found that a local void cannot satisfyingly alleviate the Hubble tension, since it is not preferred over the $Λ$CDM model by the observations such as the Pantheon SNIa sample, especially in terms of the information criteria AIC and BIC. In the present work, we try to alleviate the Hubble tension with a local void and transitions of the absolute magnitude $M$, by using the Pantheon+ SNIa sample alone or jointly with the CMB data of Planck 2018. We find that the Hubble tension can be satisfyingly alleviated, while the $Λ$LTB void models are strongly preferred by the observations.
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Submitted 11 August, 2025; v1 submitted 17 April, 2025;
originally announced April 2025.
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Cosmological constraints on dark energy models using DESI BAO 2024
Authors:
Jie Zheng,
Da-Chun Qiang,
Zhi-Qiang You
Abstract:
Recently, the measurements of baryon acoustic oscillations (BAO) by the Dark Energy Spectroscopic Instrument (DESI) indicate a potential deviation from the standard $Λ$CDM model. Some studies suggest that the data points from the luminous red galaxies (LRG) survey in DESI BAO data may contribute to this discrepancy. In this work, our main goal is to investigate whether this deviation is caused by…
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Recently, the measurements of baryon acoustic oscillations (BAO) by the Dark Energy Spectroscopic Instrument (DESI) indicate a potential deviation from the standard $Λ$CDM model. Some studies suggest that the data points from the luminous red galaxies (LRG) survey in DESI BAO data may contribute to this discrepancy. In this work, our main goal is to investigate whether this deviation is caused by the parameterization of the equation of state (EoS) of dark energy (DE). Hence, we have examined four popular parameterized dark energy models in our analysis: the Chevallier-Polarski-Linder (CPL), Barboza-Alcaniz (BA), Jassal-Bagla-Padmanabhan (JBP), and Feng-Shen-Li-Li (FSLL) parameterizations. Considering that LRG1 and LRG2 data points may lead to deviation from the $Λ$CDM model, we use two versions of DESI BAO data, differing in whether these data points are included. Additionally, to break the parameter degeneracies and obtain robust constraint results, we introduce Type Ia supernovae (SNe Ia) and quasars (QSO) in our analysis. Our findings indicate that in these parameterizations, the deviation from ($w_0$,$w_{1}$)=(-1,0) becomes more pronounced when using the combined data from DESI BAO, SNe Ia, and QSO compilations. Here, $w_{0}$ and $w_{1}$ represent the EoS of DE. It suggests that the parameterizations of the EoS of DE have little impact on the deviation from the $Λ$CDM model. Besides, our analysis potentially hints that dark energy may have dynamic properties. In addition, the results obtained from different BAO datasets demonstrate that the LRG1 and LRG2 data points do indeed contribute to a deviation from the $Λ$CDM model. Finally, according to the statistical criteria, the Akaike Information Criterion (AIC) and the Bayesian Information Criterion (BIC), the joint constraints provide substantial observational support to the BA and FSLL models.
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Submitted 6 December, 2024;
originally announced December 2024.
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Unsupervised Machine Learning for Classifying CHIME Fast Radio Bursts and Investigating Empirical Relations
Authors:
Da-Chun Qiang,
Jie Zheng,
Zhi-Qiang You,
Sheng Yang
Abstract:
Fast Radio Bursts (FRBs) are highly energetic millisecond-duration astrophysical phenomena typically categorized as repeaters or non-repeaters. However, observational limitations may result in misclassifications, potentially leading to a higher proportion of repeaters than currently identified. In this study, we leverage unsupervised machine learning techniques to classify FRBs using data from the…
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Fast Radio Bursts (FRBs) are highly energetic millisecond-duration astrophysical phenomena typically categorized as repeaters or non-repeaters. However, observational limitations may result in misclassifications, potentially leading to a higher proportion of repeaters than currently identified. In this study, we leverage unsupervised machine learning techniques to classify FRBs using data from the CHIME/FRB catalogs, including both the first catalog and a recent repeater catalog. By employing Uniform Manifold Approximation and Projection for dimensionality reduction and clustering algorithms (k-means and Hierarchical Density-Based Spatial Clustering of Applications with Noise), we successfully segregate repeaters and non-repeaters into distinct clusters, identifying over 100 potential repeater candidates. Our analysis reveals several empirical relations within the clusters, including the ${\rm log \,}Δt_{sc}-{\rm log \,}Δt_{rw}$, ${\rm log \,}Δt_{sc}-{\rm log \,}T_B$, and $r - γ$ correlations, where ${Δt_{sc}, Δt_{rw}, T_B, r, γ}$ represent scattering time, rest-frame width, brightness temperature, spectral running, and spectral index, respectively. The Chow test results reveal that while some repeaters and non-repeaters share similar empirical relationships, the overall distinctions between the two groups remain significant, reinforcing the classification of FRBs into repeaters and non-repeaters. These findings provide new insights into the physical properties and emission mechanisms of FRBs. This study demonstrates the effectiveness of unsupervised learning in classifying FRBs and identifying potential repeaters, paving the way for more precise investigations into their origins and applications in cosmology. Future improvements in observational data and machine learning methodologies are expected to further enhance our understanding of FRBs.
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Submitted 15 April, 2025; v1 submitted 21 November, 2024;
originally announced November 2024.
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3D Localization of FRB 20190425A for Its Potential Host Galaxy and Implications
Authors:
Da-Chun Qiang,
Zhiqiang You,
Sheng Yang,
Zong-Hong Zhu,
Ting-Wan Chen
Abstract:
Fast radio bursts (FRBs) are high-energy, short-duration phenomena in radio astronomy. Identifying their host galaxies can provide insights into their mysterious origins. In this paper, we introduce a novel approach to identifying potential host galaxies in three-dimensional space. We use FRB 20190425A and GW190425 as an example to illustrate our method. Recently, due to spatial and temporal proxi…
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Fast radio bursts (FRBs) are high-energy, short-duration phenomena in radio astronomy. Identifying their host galaxies can provide insights into their mysterious origins. In this paper, we introduce a novel approach to identifying potential host galaxies in three-dimensional space. We use FRB 20190425A and GW190425 as an example to illustrate our method. Recently, due to spatial and temporal proximity, the potential association of GW190425 with FRB 20190425A has drawn attention, leading to the identification of a likely host galaxy, UGC 10667, albeit without confirmed kilonova emissions. We search for the host galaxy of FRB 20190425A with a full CHIME localization map. Regardless of the validity of the association between GW190425 and FRB 20190425A, we identify an additional potential host galaxy (SDSS J171046.84+212732.9) from the updated GLADE galaxy catalog, supplementing the importance of exploring the new volume. We employed various methodologies to determine the most probable host galaxy of GW190424 and FRB 20190425A, including a comparison of galaxy properties and constraints on their reported observation limits using various Kilonova models. Our analysis suggests that current observations do not definitively identify the true host galaxy. Additionally, the Kilonova models characterized by a gradual approach to their peak are contradicted by the observational upper limits of both galaxies. Although the absence of optical emission detection raises doubts, it does not definitively disprove the connection between GW and FRB.
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Submitted 22 January, 2025; v1 submitted 21 November, 2024;
originally announced November 2024.
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Checking the Empirical Relations with the Current Localized Fast Radio Bursts
Authors:
Lin-Yu Li,
Jing-Yi Jia,
Da-Chun Qiang,
Hao Wei
Abstract:
Although fast radio bursts (FRBs) were discovered more than a decade ago, and they have been one of the active fields in astronomy and cosmology, their origins are still unknown. An interesting topic closely related to the origins of FRBs is their classifications. Different classes of FRBs require different physical mechanisms. If some empirical relations are found for different classes of FRBs, t…
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Although fast radio bursts (FRBs) were discovered more than a decade ago, and they have been one of the active fields in astronomy and cosmology, their origins are still unknown. An interesting topic closely related to the origins of FRBs is their classifications. Different classes of FRBs require different physical mechanisms. If some empirical relations are found for different classes of FRBs, they might justify the classifications scenario and help us to reveal the physical mechanisms behind. On the other hand, FRBs are actually a promising probe for cosmology, since their redshifts could be $z\sim 3$ or even higher. Similar to the cosmology of type Ia supernovae (SNIa) or Gamma-ray bursts (GRBs), some empirical relations might also play an important role in the FRB cosmology. In the literature, some new classifications of FRBs different from repeaters and non-repeaters were proposed recently. In particular, it was suggested to classify FRBs into the ones associated with old or young stellar populations, and some empirical relations have also been found for them, respectively. One of these empirical relations (namely $L_ν-E$ relation) without dispersion measure (DM) has been used to calibrate FRBs as standard candles for cosmology. This shows the potential of the new classification and the empirical relations for FRBs. Nowadays, more than 50 FRBs have been well localized, and hence their redshifts $z$ are observationally known. So, it is of interest to check the empirical relations with the actual data of current localized FRBs. We find that many empirical relations still hold, and in particular the one used to calibrate FRBs as standard candles for cosmology stands firm. This is beneficial to the FRB cosmology.
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Submitted 10 August, 2025; v1 submitted 23 August, 2024;
originally announced August 2024.
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Fast Radio Burst Distributions Consistent with the First CHIME/FRB Catalog
Authors:
Da-Chun Qiang,
Shu-Ling Li,
Hao Wei
Abstract:
Currently, fast radio bursts (FRBs) have become a very active field in astronomy and cosmology. However, the origin of FRBs is still unknown to date. The studies on the intrinsic FRB distributions might help us to reveal the possible origins of FRBs, and improve the simulations for FRB cosmology. Recently, the first CHIME/FRB catalog of 536 events was released. Such a large uniform sample of FRBs…
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Currently, fast radio bursts (FRBs) have become a very active field in astronomy and cosmology. However, the origin of FRBs is still unknown to date. The studies on the intrinsic FRB distributions might help us to reveal the possible origins of FRBs, and improve the simulations for FRB cosmology. Recently, the first CHIME/FRB catalog of 536 events was released. Such a large uniform sample of FRBs detected by a single telescope is very valuable to test the FRB distributions. Later, it has been claimed that the FRB distribution model tracking the cosmic star formation history (SFH) was rejected by the first CHIME/FRB catalog. In the present work, we consider some empirical FRB distribution models, and find that many of them can be fully consistent with the CHIME/FRB observational data for some suitable model parameters. Notice that a suppressed evolution with respect to SFH is commonly found for FRBs. In particular, we independently confirm that the FRB distribution model tracking SFH can be rejected at very high confidence. On the other hand, all the ``successful'' models effectively require a certain degree of ``delay'' with respect to SFH. These results might shed light on the origin of FRBs and FRB cosmology.
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Submitted 20 January, 2022; v1 submitted 14 November, 2021;
originally announced November 2021.
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Effect of Redshift Distributions of Fast Radio Bursts on Cosmological Constraints
Authors:
Da-Chun Qiang,
Hao Wei
Abstract:
Nowadays, fast radio bursts (FRBs) have been a promising probe for astronomy and cosmology. However, it is not easy to identify the redshifts of FRBs to date. Thus, no sufficient actual FRBs with identified redshifts can be used to study cosmology currently. In the past years, one has to use the simulated FRBs with "known" redshifts instead. To simulate an FRB, one should randomly assign a redshif…
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Nowadays, fast radio bursts (FRBs) have been a promising probe for astronomy and cosmology. However, it is not easy to identify the redshifts of FRBs to date. Thus, no sufficient actual FRBs with identified redshifts can be used to study cosmology currently. In the past years, one has to use the simulated FRBs with "known" redshifts instead. To simulate an FRB, one should randomly assign a redshift to it from a given redshift distribution. But the actual redshift distribution of FRBs is still unknown so far. Therefore, many redshift distributions have been assumed in the literature. In the present work, we study the effect of various redshift distributions on cosmological constraints, while they are treated equally. We find that different redshift distributions lead to different cosmological constraining abilities from the simulated FRBs. This result emphasizes the importance to find the actual redshift distribution of FRBs, and reminds us of the possible bias in the FRB simulations due to the redshift distributions.
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Submitted 1 May, 2021; v1 submitted 31 January, 2021;
originally announced February 2021.
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Reconstructing the Fraction of Baryons in the Intergalactic Medium with Fast Radio Bursts via Gaussian Processes
Authors:
Da-Chun Qiang,
Hao Wei
Abstract:
Fast radio bursts (FRBs) are a promising new probe for astronomy and cosmology. Thanks to their extragalactic and cosmological origin, FRBs could be used to study the intergalactic medium (IGM) and the cosmic expansion. It is expected that numerous FRBs with identified redshifts will be available in the near future through the identification of their host galaxies or counterparts. $\rm DM_{IGM}$,…
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Fast radio bursts (FRBs) are a promising new probe for astronomy and cosmology. Thanks to their extragalactic and cosmological origin, FRBs could be used to study the intergalactic medium (IGM) and the cosmic expansion. It is expected that numerous FRBs with identified redshifts will be available in the near future through the identification of their host galaxies or counterparts. $\rm DM_{IGM}$, the contribution from IGM to the observed dispersion measure (DM) of FRB, carries the key information about IGM and the cosmic expansion history. We can thus study the evolution of the universe by using FRBs with identified redshifts. In the present work, we are interested in the fraction of baryon mass in the IGM, $f_{\rm IGM}$, which is useful to study the cosmic expansion and the problem of the "missing baryons". We propose to reconstruct the evolution of $f_{\rm IGM}$ as a function of redshift $z$ with FRBs via a completely model-independent method, namely Gaussian processes. Since there is not a large sample of FRBs with identified redshifts, we use simulated FRBs instead. Through various simulations, we show that this methodology works well.
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Submitted 20 April, 2020; v1 submitted 24 February, 2020;
originally announced February 2020.
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Neutron Star as a Mirror for Gravitational Waves
Authors:
Hao Wei,
Da-Chun Qiang,
Zhong-Xi Yu,
Hua-Kai Deng
Abstract:
Gravitational wave (GW) has become one of the most active fields in physics and astronomy since the first direct detection of GW event in 2015. As is well known, multiple images of GW events are possible through the gravitational lenses. Here, we propose a novel mirror imaging mechanism for GW events different from the gravitational lens. In the literature, the superconductor was predicted to be h…
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Gravitational wave (GW) has become one of the most active fields in physics and astronomy since the first direct detection of GW event in 2015. As is well known, multiple images of GW events are possible through the gravitational lenses. Here, we propose a novel mirror imaging mechanism for GW events different from the gravitational lens. In the literature, the superconductor was predicted to be highly reflective mirror for GWs. It is well known that neutron stars exhibit superconductivity and superfluidity. In this work, we predict that there are two types of GW mirror imaging phenomena caused by the neutron star located in Milky Way or the same host galaxy of GW source, which might be detected within a life period of man (namely the time delay $Δt$ can be a few years to a few tens of years). It is expected to witness this predicted GW mirror imaging phenomenon in the near future. In the long term, the observations of this novel GW mirror imaging phenomenon might help us to find numerous neutron stars unseen by other means, and learn more about the complicated internal structures of neutron stars, as well as their equations of state.
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Submitted 24 September, 2020; v1 submitted 11 November, 2019;
originally announced November 2019.
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Cosmic Anisotropy and Fast Radio Bursts
Authors:
Da-Chun Qiang,
Hua-Kai Deng,
Hao Wei
Abstract:
In the recent years, the field of fast radio bursts (FRBs) is thriving and growing rapidly. It is of interest to study cosmology by using FRBs with known redshifts. In the present work, we try to test the possible cosmic anisotropy with the simulated FRBs. In particular, we only consider the possible dipole in FRBs, rather than the cosmic anisotropy in general, while the analysis is only concerned…
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In the recent years, the field of fast radio bursts (FRBs) is thriving and growing rapidly. It is of interest to study cosmology by using FRBs with known redshifts. In the present work, we try to test the possible cosmic anisotropy with the simulated FRBs. In particular, we only consider the possible dipole in FRBs, rather than the cosmic anisotropy in general, while the analysis is only concerned with finding the rough number of necessary data points to distinguish a dipole from a monopole structure through simulations. Noting that there is no a large sample of actual data of FRBs with known redshifts by now, simulations are necessary to this end. We find that at least 2800, 190, 100 FRBs are competent to find the cosmic dipole with amplitude 0.01, 0.03, 0.05, respectively. Unfortunately, even 10000 FRBs are not competent to find the tiny cosmic dipole with amplitude of ${\cal O}(10^{-3})$. On the other hand, at least 20 FRBs with known redshifts are competent to find the cosmic dipole with amplitude 0.1. We expect that such a big cosmic dipole could be ruled out by using only a few tens of FRBs with known redshifts in the near future.
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Submitted 6 September, 2020; v1 submitted 10 February, 2019;
originally announced February 2019.