A5016651832- Cosmology and Gravitation Theories
- Dark Matter and Cosmic Phenomena
- Galaxies: Formation, Evolution, Phenomena
- Astronomy and Astrophysical Research
- Black Holes and Theoretical Physics
- Astrophysics and Cosmic Phenomena
- Radio Astronomy Observations and Technology
- Computational Physics and Python Applications
- demographic modeling and climate adaptation
- Stellar, planetary, and galactic studies
- Space Science and Extraterrestrial Life
- Geophysics and Gravity Measurements
- Relativity and Gravitational Theory
- Earth Systems and Cosmic Evolution
- Solar and Space Plasma Dynamics
- Particle physics theoretical and experimental studies
- Pulsars and Gravitational Waves Research
University of Pennsylvania
2020-2024
University of Chicago
2024
California University of Pennsylvania
2024
Johns Hopkins University
2016-2020
Early dark energy (EDE) that behaves like a cosmological constant at early times (redshifts z≳3000) and then dilutes away radiation or faster later can solve the Hubble tension. In these models, sound horizon decoupling is reduced resulting in larger value of parameter H0 inferred from cosmic microwave background (CMB). We consider two physical models for this EDE, one involving an oscillating scalar field another slowly rolling field. perform detailed calculation evolution perturbations...
Precise measurements of the cosmic microwave background (CMB) power spectrum are in excellent agreement with predictions standard $\Lambda$CDM cosmological model. However, there is some tension between value Hubble parameter $H_0$ inferred from CMB and that observations Universe at lower redshifts, unusually small dark-energy density a puzzling ingredient In this paper, we explore scenario new exotic energy behaves like constant early times then decays quickly critical redshift $z_c$. An...
Cosmological observations are used to test for imprints of an ultralight axionlike field (ULA), with a range potentials $V(\ensuremath{\phi})\ensuremath{\propto}[1\ensuremath{-}\mathrm{cos}(\ensuremath{\phi}/f){]}^{n}$ set by the axion-field value $\ensuremath{\phi}$ and decay constant $f$. Scalar dynamics dictate that is initially frozen then begins oscillate around its minimum when Hubble parameter drops below some critical value. For $n=1$, once dynamical, axion energy density dilutes as...
The Hubble tension between the ΛCDM-model-dependent prediction of current expansion rate H0 using Planck data and direct, model-independent measurements in local universe from SH0ES collaboration disagree at >3.5σ. Moreover, there exists a milder ∼ 2σ similar predictions for amplitude S8 matter fluctuations its measurement universe. As explanations relying on unresolved systematics have not been found, theorists exploring these anomalies that modify cosmological model, altering...
Early dark energy (EDE) offers a particularly interesting theoretical approach to the Hubble tension, albeit one that introduces its own set of challenges, including new ``why then'' problem related EDE injection time at matter-radiation equality, and mild worsening large-scale structure (LSS) tension. Both these challenges center on properties matter, which becomes dominant component Universe is also responsible for seeding LSS. Motivated by this, we present potential couplings between...
A new component added to the standard model of cosmology that behaves like a cosmological constant at early times and then dilutes away as radiation or faster can resolve Hubble tension. We show rolling axion coupled non-Abelian gauge group exhibits behavior such an extra background level present natural particle-physics solution compare contribution this bottom-up phenomenological fluid approximation determine CMB observables sensitive only evolution Universe are expected be similar in both...
Observations by HAWC and Milagro have detected bright spatially extended TeV gamma-ray sources surrounding the Geminga Monogem pulsars. We argue that these observations, along with a substantial population of other coincident pulsar wind nebulae, constitute new morphological class halos. show HAWCs wide field-of-view unlocks an expansive parameter space halos not observable atmospheric Cherenkov telescopes. Under assumption are typical middle-aged pulsars, we ten-year observations should...
Thermal friction offers a promising solution to the Hubble and large-scale structure (LSS) tensions. This additional acts on scalar field in early universe extracts its energy density into dark radiation, cumulative effect being similar that of an (EDE) scenario. The radiation automatically redshifts at minimal necessary rate improve tension. On other hand, addition extra Universe can mitigate LSS We explore this model light cosmic microwave background (CMB), baryon acoustic oscillation,...
Early dark energy is a promising potential resolution of the Hubble tension. Unfortunately, many models suffer from need to fine-tune their initial conditions ensure that epoch early coincides with matter-radiation equality. We propose class attractive where this coincidence arises naturally as saddle point dynamical system attracts large volume phase-space trajectories regardless conditions. The approaches global attractor at late-times. Our framework therefore unifies and late using single...
Frequentist profile likelihoods have seen a resurgence in cosmology, offering an alternative to Bayesian methods as they can circumvent the impact of prior-volume effects. This paper presents Procoli, fast and accessible package obtain available on GitHub PyPI. Procoli seamlessly integrates with MontePython, incorporating all its data likelihoods, well any modified versions CLASS. provides comprehensive overview code, detailing simulated-annealing optimizer at core sequential computation...
Recent measurements of cosmic-ray electron and positron spectra at energies from a GeV to 5 TeV, as well radio, X-ray wide range gamma-ray observations pulsar-wind nebulae, indicate that pulsars are significant sources high-energy electrons positrons. Here we calculate the local $e^\pm$ energy taking into account models for (a) distribution spin-down properties; (b) source spectra; (c) physics propagation. We then use measured fluxes AMS-02, CALET DAMPE constrain space pulsar...
We explore a reparametrization of the lensing amplitude tension between weak (WL) and cosmic microwave background (CMB) data its implications for joint resolution with Hubble tension. Specifically, we focus on over scale 12 Mpc in absolute distance units using derived parameter ${S}_{12}$ show constraints from recent surveys comparison Planck 2018. In WL alone, find that convention correlates ${H}_{0}$. Accounting this correlation 3D space...
In this work, we quantify the cosmological signatures of dark energy radiation—a novel description energy, which proposes that dynamical component is comprised a thermal bath relativistic particles sourced by friction from slowly rolling scalar field. For minimal model with particle production emerging first principles, find abundance radiation can be as large <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:msub><a:mi...
Pulsars have been invoked to explain the origin of recently observed high-energy Galactic cosmic-ray positrons. Since positron propagation distance decreases with energy, number pulsars that can contribute positrons from $O(10^3)$ for energies $E\gtrsim10$ GeV only a few $E \gtrsim 500$ GeV. Thus, if these positrons, energy spectrum should become increasingly bumpy at higher energies. Here we present power-spectrum analysis be applied seek such spectral features in and combined...
Thermal friction offers a promising solution to the Hubble and large-scale structure (LSS) tensions. This additional acts on scalar field in early universe extracts its energy density into dark radiation, cumulative effect being similar that of an (EDE) scenario. The radiation automatically redshifts at minimal necessary rate improve tension. On other hand, addition extra Universe can LSS We explore this model light cosmic microwave background (CMB), baryon acoustic oscillation supernova...
Early dark energy is a promising potential resolution of the Hubble tension. Unfortunately, many models suffer from need to fine-tune their initial conditions ensure that epoch early coincides with matter-radiation equality. We propose class attractive where this coincidence arises naturally as saddle point dynamical system attracts large volume phase-space trajectories regardless conditions. The approaches global attractor at late-times. Our framework therefore unifies and late using single...