A5089582198- Cosmology and Gravitation Theories
- Black Holes and Theoretical Physics
- Galaxies: Formation, Evolution, Phenomena
- Geophysics and Gravity Measurements
- Particle physics theoretical and experimental studies
- Solar and Space Plasma Dynamics
- Dark Matter and Cosmic Phenomena
- Noncommutative and Quantum Gravity Theories
- Neutrino Physics Research
- Stochastic processes and financial applications
- Advanced Differential Geometry Research
- Astrophysics and Cosmic Phenomena
- Pulsars and Gravitational Waves Research
- Relativity and Gravitational Theory
- Advanced Thermodynamics and Statistical Mechanics
- Computational Physics and Python Applications
- Geometric Analysis and Curvature Flows
- Electromagnetic Scattering and Analysis
- Scientific Research and Discoveries
- Numerical methods in inverse problems
- Spectral Theory in Mathematical Physics
- Advanced Mathematical Modeling in Engineering
- Quantum Electrodynamics and Casimir Effect
- Gamma-ray bursts and supernovae
- Quantum Chromodynamics and Particle Interactions
The Abdus Salam International Centre for Theoretical Physics (ICTP)
2015-2024
Institute for Fundamental Physics of the Universe
2019-2023
Institute for Advanced Study
2014
Harvard University
2003-2006
Thomas Jefferson National Accelerator Facility
2004
Scuola Normale Superiore
1999-2002
European Organization for Nuclear Research
2002
Istituto Nazionale di Fisica Nucleare, Sezione di Pisa
1999-2002
The observation of GW170817 and its electromagnetic counterpart implies that gravitational waves travel at the speed light, with deviations smaller than a few×10−15. We discuss consequences this experimental result for models dark energy modified gravity characterized by single scalar degree freedom. To avoid tuning, must be unaffected not only our particular cosmological solution but also nearby solutions obtained slightly changing matter abundance. For to happen, coefficients various...
We point out the existence of a consistency relation involving 3-point function scalar perturbations which is valid in any inflationary model, independently inflaton Lagrangian under assumption that only dynamical field. The limit one momenta much smaller than other two fixed terms power spectrum and its tilt. This relation, although very hard to verify experimentally, could be easily proved wrong by forecoming data, thus ruling scenario with single field model independent way.
We propose a new scenario for early cosmology, where an inflationary de Sitter phase is obtained with ghost condensate. The transition to radiation dominance triggered by the itself, without any slow-roll potential. Density perturbations are generated fluctuations around condensate and can be reliably computed in effective field theory. scale invariant as consequence of symmetries; however, size parametrically different from conventional inflation, inflation happens at far lower energy...
We study the dependence on configuration in momentum space of primordial three-point function density perturbations several different scenarios: standard slow-roll inflation, curvaton and variable decay models, ghost models with higher derivative operators DBI model inflation. define a cosine between distributions using measure based ability experiments to distinguish them. find that fall into two broad categories fairly orthogonal distributions: where non-Gaussianity is created crossing...
We develop a method for constraining the level of non-Gaussianity density perturbations when three-point function is 'equilateral' type. Departures from Gaussianity this form are produced by single field models such as ghost or Dirac–Born–Infeld inflation and in general presence higher order derivative operators effective Lagrangian inflaton. show that induced shape can be very well approximated factorizable form, making analysis practical. also that, unless one has full sky map with uniform...
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 generic single-field dark energy models, by a parametrization of the most general theory their perturbations around given background, including higher derivative terms. In appropriate limits this approach reproduces standard quintessence, k-essence and ghost condensation. find no pathology associated to an equation state wQ < −1 or in crossing phantom divide = −1. Stability requires that side behaves, on cosmological scales, as fluid with virtually zero speed sound. This implies one...
We present a bouncing cosmology which evolves from the contracting to expanding phase in smooth way, without developing instabilities or pathologies and remaining regime of validity 4d effective field theory. A nearly scale invariant spectrum perturbations is generated during by an isocurvature scalar with negative exponential potential then converted adiabatic. The model predicts slightly blue spectrum, n_S >~ 1, no observable gravitational waves high (but dependent) level non-Gaussianities...
We study the impact of higher dimension operators in inflaton Lagrangian on non-Gaussianity scalar spectrum. These terms can strongly enhance effect without spoiling slow-roll, though it is difficult to exceed fNL~1, because scale which suppresses cannot be too low, if we want effective field theory description make sense. In particular explicitly calculate three-point function given by an derivative interaction form (∇ϕ)4, expected give most important contribution. The angular dependence...
We propose a novel cosmological scenario, in which standard inflation is replaced by an expanding phase with drastic violation of the Null Energy Condition (NEC): \dot H >> H^2. The model based on recently introduced Galileon theories, that allow NEC violating solutions without instabilities. unperturbed solution describes Universe asymptotically Minkowski past, expands increasing energy density until it exits regime validity effective field theory and reheats. This dynamical attractor...
We present a new model of inflation in which the inflaton is extra component gauge field 5D theory compactified on circle. The chief merit this that potential comes only from nonlocal effects so its flatness not spoiled by higher-dimensional operators or quantum gravity corrections. predicts red spectrum (n approximately 0.96) and significant production gravitational waves (r 0.11). also comment relevance idea to quintessence.
We generalize the single-field consistency relations to capture not only leading term in squeezed limit — going as 1/q3, where q is small wavevector but also subleading one, 1/q2. This term, for an (n+1)-point function, fixed terms of variation n-point function under a special conformal transformation; this parallels fact that 1/q3 related with scale dependence function. For 3-point relation implies there are no verify 4-point both case canonical slow-roll inflation and models reduced speed...
We derive consistency relations for the late universe (CDM and ΛCDM): between an n-point function of density contrast δ (n+1)-point in limit which one (n+1) momenta becomes much smaller than others. These are based on observation that a long mode, single-field models inflation, reduces to diffeomorphism since its freezing during inflation all way until universe, even when mode is inside horizon (but out sound horizon). results derived Newtonian gauge, at first second order small momentum q...
We show that the prediction for primordial tensor power spectrum cannot be modified at leading order in derivatives. Indeed, one can always set to unity speed of propagation gravitational waves during inflation by a suitable disformal transformation metric, while conformal make Planck mass time independent. Therefore, amplitude unambiguously fixes energy scale inflation. Using effective field theory inflation, we check predictions are independent choice frame, as expected. The first...
We study the decay of gravitational waves into dark energy fluctuations $\pi$, through processes $\gamma \to \pi\pi$ and \gamma \pi$, made possible by spontaneous breaking Lorentz invariance. Within EFT Dark Energy (or Horndeski/beyond Horndeski theories) first process is large for operator $\frac12 \tilde m_4^2(t) \, \delta g^{00}\, \left( {}^{(3)}\! R + K_\mu^\nu K^\mu_\nu -\delta K^2 \right)$, so that recent observations force $\tilde m_4 =0$ equivalently $\alpha_{\rm H}=0$). This...
We study the stability of spatially flat FRW solutions which are geodesically complete, i.e. for one can follow null (graviton) geodesics both in past and future without ever encountering singularities. This is case NEC-violating cosmologies such as smooth bounces or approach Minkowski past. EFT linear perturbations around a solution this kind, including possibility multiple fields fluids. One generally faces gradient instability be avoided only if operator (3) R δ N present its coefficient...
We point out that dark-energy perturbations may become unstable in the presence of a gravitational wave sufficiently large amplitude. study this effect for cubic Horndeski operator (braiding), proportional to $\alpha_{\rm B}$. The scalar describes fluctuations features ghost and/or gradient instabilities gravitational-wave amplitudes are produced by typical binary systems. Taking into account populations systems, we conclude instability is triggered whole Universe $|\alpha_{\rm B} |\gtrsim...
We analyse the three-year Wilkinson Microwave Anisotropy Probe data and look for a deviation from Gaussianity in form of three-point function that has either two theoretically motivated shapes: local equilateral. There is no evidence departure analysis gives currently tightest bounds on parameters fNLlocal fNLequil, which define amplitudes respectively non-Gaussianity equilateral non-Gaussianity: −36 < 100, −256 fNLequil 332 at 95% C.L.
A new and powerful probe of the origin evolution structures in Universe has emerged been actively developed over last decade. In coming decade, non-Gaussianity, i.e., study non-Gaussian contributions to correlations cosmological fluctuations, will become an important both early late Universe. Specifically, it play a leading role furthering our understanding two fundamental aspects cosmology astrophysics: (i) physics very universe that created primordial seeds for large-scale structures, (ii)...
We study the consequences of imposing an approximate Galilean symmetry on Effective Theory Inflation, theory small perturbations around inflationary background. This approach allows us to effect operators with two derivatives each field, which can be leading interactions due non-renormalization properties Lagrangian. In this case cubic non-Gaussianities are given by three independent operators, containing up six derivatives, a shape close equilateral and one peaking flattened isosceles...