A5047576925- Cosmology and Gravitation Theories
- Black Holes and Theoretical Physics
- Galaxies: Formation, Evolution, Phenomena
- Advanced Mathematical Theories and Applications
- Noncommutative and Quantum Gravity Theories
- Pulsars and Gravitational Waves Research
- Geophysics and Gravity Measurements
- Gyrotron and Vacuum Electronics Research
- Microwave Engineering and Waveguides
- Advanced Mathematical Physics Problems
- Dark Matter and Cosmic Phenomena
- Mechanical and Optical Resonators
- Advanced Antenna and Metasurface Technologies
- Quantum Electrodynamics and Casimir Effect
- Radio Astronomy Observations and Technology
- Quantum Chromodynamics and Particle Interactions
- Computational Physics and Python Applications
- Atomic and Subatomic Physics Research
- Quantum chaos and dynamical systems
- Matrix Theory and Algorithms
- Nosocomial Infections in ICU
- Complex Systems and Time Series Analysis
- Quantum many-body systems
- Photonic and Optical Devices
- Statistical and numerical algorithms
Scuola Normale Superiore
2023-2025
Leiden University
2021-2024
University of Amsterdam
2017-2024
Lorentz Center
2020-2021
Columbia University
2021
National Taiwan University
2021
Czech Academy of Sciences, Institute of Physics
2020
University of Cambridge
2015-2017
Delta Institute for Theoretical Physics
2017
Princeton University
2009-2014
Scattering amplitudes at weak coupling are highly constrained by Lorentz invariance, locality and unitarity, depend on model details only through constants the particle content of theory. For example, four-particle analytic for contact interactions have simple poles with appropriately positive residues tree-level exchange. In this paper, we develop an understanding inflationary correlators which parallels that flat-space scattering amplitudes. Specifically, study slow-roll inflation...
We study the imprints of massive particles with spin on cosmological correlators. Using framework effective field theory inflation, we classify couplings these to Goldstone boson broken time translations and graviton. show that it is possible generate observable non-Gaussianity within regime validity theory, as long masses are close Hubble scale their interactions break approximate conformal symmetry inflationary background. derive explicit shape functions for scalar tensor bispectra can...
A bstract key insight of the bootstrap approach to cosmological correlations is fact that all correlators slow-roll inflation can be reduced a unique building block — four-point function conformally coupled scalars, arising from exchange massive scalar. Correlators corresponding particles with spin are then obtained by applying spin-raising operator scalar-exchange solution. Similarly, massless external fields derived acting suitable weight-raising operator. In this paper, we present...
We extend the cosmological bootstrap to correlators involving massless particles with spin. In de Sitter space, these are constrained both by symmetries and locality. particular, isometries become conformal on future boundary of spacetime, which reflected in a set Ward identities that must satisfy. solve acting weight-shifting operators scalar seed solutions. Using this approach, we derive three- four-point spin-1 spin-2 fields conformally coupled scalars. Four-point functions arising from...
A bstract Much of the structure cosmological correlators is controlled by their singularities, which in turn are fixed terms flat-space scattering amplitudes. An important challenge to interpolate between singular limits determine full at arbitrary kinematics. This particularly relevant because singularities not directly observable, but can only be accessed analytic continuation. In this paper, we study rational — including those gauge fields, gravitons, and inflaton whose tree level poles...
Abstract Primordial non-Gaussianities from multi-field inflation are a leading target for cosmological observations, because of the possible large correlations generated between long and short distances. These signatures captured by local shape scalar bispectrum. In this paper, we revisit nonlinearities conversion process additional light scalars into curvature perturbations during inflation. We provide analytic templates correlation functions valid at any kinematical configuration, using...
This white paper summarizes recent progress in the cosmologicalbootstrap, an approach to study of statistics primordialfluctuations from consistency with unitarity, locality and symmetryassumptions. We review key ideas bootstrap method, aneye towards future directions ambitions program. Focusing onrecent involving de Sitter quasi-de backgrounds, wehighlight role singularities unitarity constraining theform correlators. also discuss nonperturbative formulations ofthe bootstrap, connections...
A bstract Massless spinning correlators in cosmology are extremely complicated. In contrast, the scattering amplitudes of massless particles with spin very simple. We propose that reason for unreasonable complexity these lies use inconvenient kinematic variables. For example, de Sitter space, consistency unitarity and background isometries imply must be conformally covariant also conserved. However, commonly used variables do not make all properties manifest. this paper, we introduce twistor...
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...
A bstract Cosmological correlation functions contain valuable information about the primordial Universe, with possible signatures of new massive particles at very high energies. Recent developments, including cosmological bootstrap, bring perspectives and powerful tools to study these observables. In this paper, we systematically classify inflationary three-point correlators scalar perturbations using bootstrap method. For first time, derive a complete set single-exchange collider bispectra...
A bstract Extending scattering to states with unphysical mass values (particles “off their shell”) has been instrumental in developing modern amplitude technology for Minkowski spacetime. Here, we study the off-shell correlators which underpin recently proposed S -matrix on de Sitter By labelling each particle both a spatial momentum and an independent “energy” variable (the analogue of 4-momentum), find that practical computation these is greatly simplified. This allows us derive compact...
Studying loop corrections to inflationary perturbations, with particular emphasis on infrared factors, is important understand the consistency of theory, its predictivity and establish existence slow-roll eternal inflation phenomena recently found volume bound. In this paper we prove that zeta correlation function time-independent at one-loop level in single clock inflation. While many diagrams lead a time-dependence when considered individually, beautifully cancels out overall sum. We...
In this paper, we explore a novel observational signature of gravitational corrections during slow-roll inflation. We study the coupling inflaton field to higher-curvature tensors in models with minimal breaking conformal symmetry. that case, most general correction tensor two-point function is captured by square Weyl tensor. show these scenarios lead tilt power spectrum and hence violation consistency condition. arrive at same conclusion through an analysis perturbation theory.
Our current understanding of the Universe is established through pristine measurements structure in cosmic microwave background (CMB) and distribution shapes galaxies tracing large scale (LSS) Universe. One key ingredient that underlies cosmological observables field sources observed assumed to be initially Gaussian with high precision. Nevertheless, a minimal deviation from Gaussianityis perhaps most robust theoretical prediction models explain Universe; itis necessarily present even...
It is shown that the squeezed limit of inflationary expectation values follows from reparametrization invariance wavefunction universe. This translates into a constraint on longitudinal modes functional derivatives wavefunction. Thus, local non-Gaussianity induced by single field inflation purely gauge artifact. We focus Einstein gravity in de Sitter space and inflation, although formalism only relies diffeomorphism theory, thus applies to any theory gravity.
The representation theory of de Sitter space allows for a category partially massless particles which have no flat analog, but could existed during inflation. We study the couplings these exotic to inflationary perturbations and determine resulting signatures in cosmological correlators. When interact through exchange fields, their correlation functions inherit scalings that cannot be mimicked by extra massive fields. discuss detail squeezed limit tensor-scalar-scalar bispectrum, show...
Objective: To assess the structural characteristics involved in design of high-volume low-pressure endotracheal tube cuffs that are associated with fluid sealing effectiveness and to determine extent transmitted tracheal pressures upon cuff inflation. Design: In vitro study. Settings: Pneumology laboratories. Interventions: Eight cylindrical or tapered shape, made polyvinylchloride polyurethane, were studied. Cuffs tested within a model, oriented 30° above horizontal 1 hr leakage...
This white paper summarizes recent progress in the cosmological bootstrap, an approach to study of statistics primordial fluctuations from consistency with unitarity, locality and symmetry assumptions. We review key ideas bootstrap method, eye towards future directions ambitions program. Focusing on involving de Sitter quasi-de backgrounds, we highlight role singularities unitarity constraining form correlators. also discuss nonperturbative formulations connections anti-de space, potential...
Abstract We study the cosmic variance limit on constraining primordial non-Gaussianity for a variety of theory-motivated shapes. consider general arguments 2D and 3D surveys, with particular emphasis CMB. A scale-invariant N -point correlator can be measured signal-to-noise that naively scales square root number observed modes. This intuition generally fails two reasons. First, scaling is reduced due to blurring last scattering surface at short distances. caused by combination projection...
Here we present a status report of the Schenberg antenna. In past three years it has gone to radical upgrading operation, in which have been installing 1K pot dilution refrigerator, cabling and amplifiers for nine transducer circuits, designing new suspension vibration isolation system microstrip antennas, developing full set transducers, oscillators. We are also studying an innovative approach, could transform into broadband gravitational wave detector.
We argue that the non-detection of primordial tensor modes has taught us a great deal about universe. In single-field slow-roll inflation, current upper bound on tensor-to-scalar ratio, $r < 0.07$ $(95 \% ~CL)$, implies Hubble parameters obey $\varepsilon \ll \eta$, and therefore establishes existence new hierarchy. dub this regime conformal limit (slow-roll) show it includes Starobinsky-like inflation as well all viable models with sub-Planckian field excursion. limit, correlators are...