A5108033261- Cosmology and Gravitation Theories
- Galaxies: Formation, Evolution, Phenomena
- Dark Matter and Cosmic Phenomena
- Black Holes and Theoretical Physics
- Geophysics and Gravity Measurements
- Solar and Space Plasma Dynamics
- Particle physics theoretical and experimental studies
- Astronomy and Astrophysical Research
- Advanced Sensor and Control Systems
- Power Transformer Diagnostics and Insulation
- Computational Physics and Python Applications
- Scientific Research and Discoveries
- Advanced Algorithms and Applications
- High voltage insulation and dielectric phenomena
- Water Quality Monitoring and Analysis
- Stellar, planetary, and galactic studies
- Electrical Fault Detection and Protection
- Industrial Technology and Control Systems
- Advanced Thermodynamics and Statistical Mechanics
- Pulsars and Gravitational Waves Research
- Spectroscopy and Chemometric Analyses
- Electric Power Systems and Control
- Laser-induced spectroscopy and plasma
- 2D Materials and Applications
- Thermal Analysis in Power Transmission
Chongqing University of Technology
2009-2025
Center for Astrophysics Harvard & Smithsonian
2016-2023
Nanjing Agricultural University
2019-2022
Harvard University Press
2021
Harvard University
2019
The University of Texas at Dallas
2013-2017
University of Cambridge
2010-2014
Massachusetts Institute of Technology
2008-2010
Cornell University
2007-2008
Kavli Institute for Theoretical Sciences
2008
We perform a general study of primordial scalar non-Gaussianities in single-field inflationary models Einstein gravity. consider where the inflaton Lagrangian is an arbitrary function field and its first derivative, sound speed arbitrary. find that under reasonable assumptions, non-Gaussianity completely determined by five parameters. In special limits parameter space, one finds distinctive ‘shapes’ non-Gaussianity. with small speed, several these shapes would become potentially observable...
In quasi-single field inflation models, massive isocurvature modes, that are coupled to the inflaton and have mass of order Hubble parameter, can nontrivial impacts on density perturbations, especially non-Gaussianities. We study a simple example in terms turning trajectory. Large bispectra with one-parameter family novel shapes arise, lying between well-known local equilateral shape. The trispectra also be very large its magnitude tNL much larger than fNL squared.
This is a pedagogical review on primordial non-Gaussianities from inflation models. We introduce formalisms and techniques that are used to compute such quantities. different mechanisms which can generate observable large during inflation, distinctive signatures they leave the non-Gaussian profiles. They potentially powerful probes dynamics of inflation. also provide nontechnical qualitative summary main results underlying physics.
Inflation driven by a single, minimally coupled, slowly rolling field generically yields negligible primordial non-Gaussianity. We discuss two distinct mechanisms which non-trivial potential can generate large non-Gaussianities. Firstly, if the inflaton traverses feature in potential, or inflationary phase is short enough so that initial transient contributions to background dynamics have not been erased, modes near horizon crossing acquire significant Secondly, potentials with small-scale...
We summarize the utility of precise cosmic microwave background (CMB) polarization measurements as probes physics inflation. focus on prospects for using CMB to differentiate various inflationary mechanisms. In particular, a detection primordial B‐mode would demonstrate that inflation occurred at very high energy scale, and inflaton traversed super‐Planckian distance in field space. explain how such or constraint illuminate aspects Planck scale. Moreover, can constrain scale‐dependence...
We study the slow-roll inflation models, where inflaton slow-rolls along a trajectory whose orthogonal directions are lifted by potentials with masses of order Hubble parameter. In these models large non-Gaussianities can be generated through transformation from isocurvature modes to curvature mode, once turns. find bispectra one-parameter family novel shapes, interpolating between equilateral and local shape. According in-in formalism, shapes different simple projection non-Gaussian...
Abstract Inflationary models predicting a scale-dependent large amplification of the density perturbations have recently attracted lot attention because amplified can seed sizable amount primordial black holes (PBHs) and stochastic background gravitational waves (GWs). While power spectra in these are computed based on linear equation motion, it is not obvious whether loop corrections negligible when such occurs during inflation. In this paper, as first step to discuss models, we use in-in...
We compute the three-point correlation function for a general model of inflation driven by single, minimally coupled scalar field. Our approach is based on numerical evaluation both perturbation equations and integrals which contribute to function. Consequently, we can analyse models where potential has 'feature', in vicinity slow roll parameters may take large, transient values. This introduces scale shape dependent non-Gaussianities into primordial perturbations. As an example our...
We study the non-Gaussianity in simplest infrared model of Dirac-Born-Infeld (DBI) inflation. show that such a is compatible with current observational bound and within sensitivity future experiments. also discuss scale dependence non-Gaussianity. In DBI inflation, feature can be used as probe to properties background geometry extra dimensions or internal space.
We present a scenario where brane inflation arises more generically. start with D3 and anti-D3-branes at the infrared ends of two different throats. This setup is natural consequence assumption that in beginning we have multithroat string compactification many wandering anti-D3-branes. A long period triggered when D3-branes slowly exit highly warped region, under potential generically arising from moduli stabilization. In this scenario, usual slow-roll conditions are not required, large...
In the primordial universe, fields with mass much larger than mass-scale of event-horizon (such as Hubble parameter in inflation) exist ubiquitously, and can be excited from time to oscillate quickly around their minima. These excitations induce specific patterns density perturbations, which record dependence scale factor thus provide direct evidence for inflation paradigm or its alternatives. Such effects are conventionally averaged out theoretical data analyses, but accessible experiments...
We present a systematic introduction to the diagrammatic method for practical calculations in inflationary cosmology, based on Schwinger-Keldysh path integral formalism. show particular that rules can be derived directly from classical Lagrangian even presence of derivative couplings. Furthermore, we use quasi-single-field inflation model as an example how this formalism, combined with trick mixed propagator, significantly simplify calculation some in-in correlation functions. The resulting...
Non-attractor inflation is known as the only single field inflationary scenario that can violate non-Gaussianity consistency relation with Bunch-Davies vacuum state and generate large local non-Gaussianity. However, it also non-attractor by itself incomplete should be followed a phase of slow-roll attractor. Moreover, there transition process between these two phases. In past literature, this was approximated instant evolution in not fully studied. paper, we follow detailed through into...
We calculate 1-loop corrections to the Schwinger-Keldysh propagators of Standard-Model-like fields spin-0, 1/2, and 1, with all renormalizable interactions during inflation. pay special attention late-time divergences loop corrections, show that can be resummed into finite results in limit using dynamical renormalization group method. This is our first step toward studying both Standard Model new physics primordial universe.
The inflationary universe can be viewed as a "cosmological collider" with an energy of the Hubble scale, producing very massive particles and recording their characteristic signals in primordial non-Gaussianities. To utilize this collider to explore any new physics at high scales, it is prerequisite understand background from particle standard model. In Letter we describe model cosmological collider.
The stochastic gravitational wave background (SGWB) offers a new opportunity to observe signals of primordial features from inflationary models. We study their detectability with future space-based waves experiments, focusing our analysis on the frequency range LISA mission. compute spectra by exploring parameter space two-field inflation model capable generating different classes features. Fine-tuning in scales and amplitudes is necessary for these fall observational windows. In some cases...
In this paper, we point out and study a generic type of signals existing in the primordial universe models, which can be used to model-independently distinguish inflation scenario from alternatives. These are generated by massive fields that function as standard clocks. The role clocks has been realized previous works. Although existence such is generic, realizations require sharp features classically excite oscillations clock fields. Here, quantum fluctuations actually serve same purpose We...
Cosmic inflation provides a window to the highest energy densities accessible in nature, far beyond those achievable any realistic terrestrial experiment. Theoretical insights into inflationary era and its observational probes may therefore shed unique light on physical laws underlying our universe. This white paper describes current theoretical understanding of era, with focus statistical properties primordial fluctuations. In particular, we survey targets for three important signatures...
Industrial wastewater containing large amounts of organic pollutants is a severe threat to the environment and human health. Thus, rapid detection removal these from are essential protect public health ecological environment. In this study, multifunctional reusable surface-enhanced Raman scattering (SERS) substrate by growing Ag nanoparticles (NPs) on ZnO nanorods (NRs) was produced for detecting degrading Rhodamine B (RhB) dye. The ZnO/Ag exhibited excellent sensitivity, limit (LOD) RhB as...
We compute the large scalar four-point correlation functions in general single field inflation models, where inflaton Lagrangian is an arbitrary function of and its first derivative. find that leading order trispectra have four different shapes determined by three parameters. study features these can be used to distinguish among themselves, between them local form. For purpose data analyses, we give two simple representative forms for ``equilateral trispectra''. also effects on if initial...
We show that brane inflation is very sensitive to tiny sharp features in extra dimensions, including those the potential and warp factor. This can up as observational signatures power spectrum and/or non-Gaussianities of cosmic microwave background radiation (CMBR). One general example such a succession small steps warped throat, caused by Seiberg duality cascade using gauge/gravity duality. study cosmological consequences these inflation. Since come series, prediction other their properties...
We study the effect of massive isocurvaton on density perturbations in quasi-single field inflation models, when mass M becomes larger than order Hubble parameter H. analytically compute correction to power spectrum, leading coupling but exact for all values mass. This verifies previous numerical results range 0<M<3H/2 and shows that, large limit, is H^2/M^2.
We compare the infrared Dirac-Born-Infeld brane inflation model to observations using a Bayesian analysis. The current data cannot distinguish it from $\ensuremath{\Lambda}\mathrm{CDM}$ but is able give interesting constraints on various microscopic parameters including mass of moduli potential, fundamental string scale, charge or warp factor throats, and number mobile branes. quantify some distinctive testable predictions with stringy signatures, such as large non-Gaussianity, large,...