Article
Astronomy & Astrophysics
Anjan A. Sen, Shahnawaz A. Adil, Somasri Sen
Summary: This study explores the possibility of a negative cosmological constant in the Universe and finds that it is consistent with observational data.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Reginald Christian Bernardo, Che-Yu Chen, Jackson Levi Said, Yu-Hsien Kung
Summary: This study investigates the effects of quantum fluctuations on the late Universe and explores a representative model with quantum fluctuations embedded in modified gravitational theories. The results suggest mild support for quantum corrections in cosmological models.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Boris Bolliet, Jens Chluba, Richard Battye
Summary: The study demonstrates that spectral distortions of the cosmic microwave background can be used to study particle physics. It calculates the distortion signals from decaying particles converting into photons at different historical epochs, and constraints on the properties of these particles are explored. Future improvements in CMB spectrometers could enhance the constraints obtained, offering an important complementary probe of early-universe particle physics.
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(2021)
Article
Astronomy & Astrophysics
Seokcheon Lee
Summary: For the varying speed of light (VSL) models to be phenomenologically feasible, at least one dimensionless physical constant must change. Adiabaticity and the dependence of physical constants and quantities on cosmic time are also important. The minimally extended VSL (meVSL) model satisfies these conditions and the redshift-drift formula is the same as the standard model. However, the meVSL cannot be verified experimentally but can be tested using cosmological chronometers (CC).
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(2023)
Article
Astronomy & Astrophysics
Seokcheon Lee
Summary: The Friedmann-Lemaitre-Robertson-Walker model establishes the correlation between redshifts and distances, incorporating the metric expansion of space. In this model, as the universe expands, the wavelength of photons is stretched, resulting in a cosmological redshift, denoted as z. The relationship between the frequency of light detected by a local observer and that emitted from a distant source is modified in the minimally extended varying speed of light model as 1/(1 + z)(1 - b/4).
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(2023)
Article
Astronomy & Astrophysics
Mahnaz Asghari, Ahmad Sheykhi
Summary: The thermodynamics-gravity conjecture suggests a reciprocal relationship between the gravitational field equations and the first law of thermodynamics. By incorporating non-extensive Tsallis entropy and applying the Clausius relation, gravitational field equations were derived, and a cosmological model based on Tsallis modified gravity was constructed. Observational data was used to constrain the cosmological parameters of the model, which showed that the model may alleviate tensions in the structure growth parameter sigma(8).
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(2021)
Article
Astronomy & Astrophysics
Lehman H. Garrison, Michael Joyce, Daniel J. Eisenstein
Summary: Self-similarity analysis in scale-free N-body simulations helps determine the spatial and temporal scales at which statistics converge to the physical continuum limit. Proper softening reaching 1/30th of inter-particle spacing by the end of the simulation can resolve similar scales as comoving softening of the same length with fewer time steps in Lambda CDM simulations. Additionally, there is an inherent resolution limit set by particle mass, beyond which reducing softening does not improve resolution, suggesting a relationship with spectral index n = -2 in Lambda CDM simulations.
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(2021)
Article
Astronomy & Astrophysics
Mehdi Rezaei, Joan Sola Peracaula, Mohammad Malekjani
Summary: This study focuses on different types of dark energy models within the cosmographic approach, finding that the running vacuum models are preferred in cosmological analysis and are successful in alleviating cosmographic tensions in observational data.
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(2022)
Article
Astronomy & Astrophysics
M. Sabiee, M. Malekjani, D. Mohammad Zadeh Jassur
Summary: In this paper, the power-law f(T) model is studied using various cosmographic methods. The study shows that the PADE (3,2) polynomial is the best approximation for reconstructing the distance modulus in the cosmographic method. The power-law f(T) model is found to be consistent with observational data, and the combination of the Hubble diagram of SNIa and the BAO observation improves the consistency between the model-independent cosmographic method and the power-law f(T) model.
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(2022)
Article
Astronomy & Astrophysics
Kieran Finn, Sotirios Karamitsos, Apostolos Pilaftsis
Summary: The classical Eisenhart lift method has been extended to quantum systems, successfully reproducing both classical and quantum effects of the potential. A conserved quantum number corresponding to the lifted momentum is identified, and in quantum field theory, a quantum charge analog of the lifted momentum is conserved in both time and space. The relevance of the extended Fock spaces to cosmological constant and gauge hierarchy problems is considered.
Article
Astronomy & Astrophysics
Sandeep Kumar Acharya, Jiten Dhandha, Jens Chluba
Summary: The excess radio background observed at similar to 0.1-10GHz has sparked scientific debate in recent years. A recent hypothesis suggests that the soft photon emission from accreting primordial black holes could explain this signal. However, our study shows that the expected ultraviolet photon emission from these accreting black holes would fully ionize the universe at z > 6, thereby diminishing the 21-cm absorption signature at z similar to 20 and conflicting with the current limits of cosmic microwave background anisotropy and average spectral distortion.
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(2022)
Article
Astronomy & Astrophysics
Sandeep Kumar Acharya, Jens Chluba, Abir Sarkar
Summary: The study compared a range of Fokker-Planck approximations for Compton scattering in astrophysical plasmas, finding that the Kompaneets equation is the most robust approximation, despite its inaccuracies at high energies. The necessity of using the scattering kernel for accurate computations of cosmic microwave background spectral distortions was demonstrated through solutions for photon injection scenarios.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Didam G. A. Duniya, Mazuba Kumwenda
Summary: The next generation of cosmological surveys will provide unprecedented precision and allow for the most stringent tests of theoretical ideas. To fully utilize these measurements, effective analytical tools and the best cosmological observables must be identified.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Sandeep Kumar Acharya, Bryce Cyr, Jens Chluba
Summary: This study reveals the link between CMB spectral distortions and 21 cm cosmology, highlighting the interplay between radio spectral distortions and associated heating. This discovery could hide a significant radio excess before reionization, and significantly impact the constraints from existing and future 21 cm observations on the radio background evolution.
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(2023)
Article
Astronomy & Astrophysics
Jin Qin, Fulvio Melia, Tong-Jie Zhang
Summary: The study introduces a new method to test the cosmic distance duality relation and finds that the formula favors a flat Universe.
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(2021)
Article
Astronomy & Astrophysics
Aditya Rotti, Jens Chluba
Summary: Researchers demonstrate the potential of measuring monopolar spectral distortion signals using Internal Linear Combination (ILC) and extended moment methods, combining the two approaches to construct MILC, which can recover tiny monopolar spectral distortion signals in the presence of realistic foregrounds and instrumental noise for the first time.
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(2021)
Article
Astronomy & Astrophysics
Aditya Rotti, Boris Bolliet, Jens Chluba, Mathieu Remazeilles
Summary: The Sunyaev-Zeldovich effect can be analyzed using either cluster number count (CNC) or power spectrum (PS) analysis. In this study, a new method was developed to combine CNC and PS analyses using a survey completeness function, providing a systematic approach to obtain two complementary y-maps. This method allows for better understanding of the SZ effect and the presence of mass-dependent biases.
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(2021)
Article
Astronomy & Astrophysics
Luke Hart, Jens Chluba
Summary: Varying fundamental constants can be constrained by measurements of the cosmic microwave background. A model-independent principal component analysis is performed to obtain new constraints on these variations. No significant departures from the standard model are found. Future improvements are anticipated. However, further research is needed to understand the origin of the Hubble tension.
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(2022)
Article
Astronomy & Astrophysics
Elizabeth Lee, Jens Chluba, Gilbert P. Holder
Summary: This paper investigates the radio Sunyaev-Zeldovich (SZ) effect caused by the cosmological radio background. The authors propose easily calculable kinematic and relativistic temperature corrections to this effect and discuss how it affects the spectrum of the radio SZ effect in different cases. By measuring the SZ signal around the radio null, constraints can be placed on the properties of the cosmological radio background, and combining it with SZ measurements from large cluster samples could help break degeneracies between different contributions.
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(2022)
Article
Astronomy & Astrophysics
Sandeep Kumar Acharya, Jens Chluba
Summary: Accurate computations of spectral distortions of the cosmic microwave background (CMB) are crucial for understanding energy release scenarios at high redshifts. This paper presents a new approach to compute the distorted CMB spectrum, taking into account non-linear effects, time-dependence of injection process, modifications to the Hubble expansion rate, and relativistic Compton scattering. The study expands our understanding of CMB spectral distortions and offers a more rigorous treatment for various scenarios.
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(2022)
Article
Astronomy & Astrophysics
Sandeep Kumar Acharya, Jiten Dhandha, Jens Chluba
Summary: The excess radio background observed at similar to 0.1-10GHz has sparked scientific debate in recent years. A recent hypothesis suggests that the soft photon emission from accreting primordial black holes could explain this signal. However, our study shows that the expected ultraviolet photon emission from these accreting black holes would fully ionize the universe at z > 6, thereby diminishing the 21-cm absorption signature at z similar to 20 and conflicting with the current limits of cosmic microwave background anisotropy and average spectral distortion.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Elizabeth Lee, Dhayaa Anbajagane, Priyanka Singh, Jens Chluba, Daisuke Nagai, Scott T. Kay, Weiguang Cui, Klaus Dolag, Gustavo Yepes
Summary: The Sunyaev-Zeldovich (SZ) effect is an important tool in cosmology. This study compares cluster temperatures predicted by different simulations and finds consistent SZ temperatures across the simulations. However, there is a systematic offset between the relativistic SZ (rSZ) temperature and other measures, with rSZ temperature being approximately 20% higher. The study also explores the variations of these measures with halo radius and investigates the effects of different feedback prescriptions and resolutions on the observed temperatures.
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(2022)
Article
Astronomy & Astrophysics
D. Paoletti, J. Chluba, F. Finelli, J. A. Rubino-Martin
Summary: We update and extend the constraints on primordial magnetic fields in the cosmic microwave background through the dissipation effects of ambipolar diffusion and magnetohydrodynamic decaying turbulence. Using the latest data release and map making algorithm, our study achieves tighter constraints on the magnetic field amplitudes.
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(2022)
Article
Astronomy & Astrophysics
Sandeep Kumar Acharya, Jens Chluba
Summary: The Sunyaev-Zeldovich effect is a widely used probe for studying cosmology through the scattering of photons from the cosmic microwave background by hot cluster electron gas. This study investigates the scattering of other photon backgrounds, specifically the cosmic infrared background (CIB), in cluster medium. The analysis reveals an underestimation of the all-sky CIB distortion due to neglecting the intracluster scattering contribution, and suggests a redshift dependence in the single-cluster CIB scattering signal, which can be utilized in future cosmological studies with CMB experiments.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Luke Hart, Jens Chluba
Summary: The cosmological recombination radiation (CRR) is a spectral distortion signal from the early Universe that can probe physical phenomena in the pre-recombination era. We study the effects of early dark energy models and varying electromagnetic fundamental constants on CRR. We provide estimates on the sensitivity of future spectrometers to these effects and suggest that a combination with Planck data is promising.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Sandeep Kumar Acharya, Bryce Cyr, Jens Chluba
Summary: This study reveals the link between CMB spectral distortions and 21 cm cosmology, highlighting the interplay between radio spectral distortions and associated heating. This discovery could hide a significant radio excess before reionization, and significantly impact the constraints from existing and future 21 cm observations on the radio background evolution.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Inigo Zubeldia, Aditya Rotti, Jens Chluba, Richard Battye
Summary: Multi-frequency matched filters (MMFs) are commonly used to detect galaxy clusters from CMB data, but estimating the cross-frequency power spectra of the noise incorrectly leads to overestimated MMF noise and biases in cosmological inference. We propose an iterative MMF (iMMF) approach that improves the estimates by reestimating the noise power spectra after the first MMF step. Applying the iMMF to Planck-like mock observations suppresses the mentioned effects and leads to more significant detections, a higher number of them, and a cluster observable with the expected theoretical properties.
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(2023)
Article
Astronomy & Astrophysics
Edoardo Altamura, Scott T. Kay, Jens Chluba, Imogen Towler
Summary: The kinetic Sunyaev-Zeldovich (kSZ) effect is an important target for studying the cosmic microwave background (CMB) and cosmology. This study investigates the rotational kSZ effect caused by large-scale motions of cluster medium using hydrodynamic cosmological simulations. The results suggest that the misalignment between dark matter, galaxy and gas spins can affect the estimation of the rotational kSZ effect. More research is needed to refine the modeling and explore the rotational kSZ effect in a wider range of masses and redshifts.
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(2023)
Article
Astronomy & Astrophysics
Sandeep Kumar Acharya, Jens Chluba
Summary: The observed excess radio background has puzzled scientists for over a decade. A recent new physics solution involves the decay of dark matter into dark photons which then convert into standard photons in the reionization era. This simple power-law model fits the current data closely, although additional work is needed to address challenges and improve the model.
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(2023)
Article
Astronomy & Astrophysics
Inigo Zubeldia, Jens Chluba, Richard Battye
Summary: Galaxy clusters detected through the tSZ effect can provide constraints on cosmological parameters, but the measured tSZ signal may be contaminated by the CIB emission. This study quantifies the contamination and proposes a spectrally constrained iMMF method (sciMMF) to suppress the CIB-induced bias from the tSZ cluster observables. The sciMMF is robust to modeling uncertainties and can be used to construct CIB-free cluster catalogues.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
