Format results
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Wormholes as Red Herrings
Jacob McNamara - Stony Brook University
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A Perturbative Window into Asymptotic Safety
Yannick Kluth - University of Toronto
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Emergent time and more from wavefunction collapse in general relativity
Sung-Sik Lee - McMaster University
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Null Musings
Luca Ciambelli - Perimeter Institute for Theoretical Physics
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Quantum Geometry of the Light Cone
Wolfgang Wieland - University of Erlangen-Nuremberg
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Spectral Density of the Causal Propagator
Yasaman Kouchekzadeh Yazdi - Dublin Institute For Advanced Studies
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An algebra of proper observables at null infinity: Dirac brackets, Memory and Goldstone probes
Rodrigo Andrade E Silva - Perimeter Institute for Theoretical Physics
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Wormholes as Red Herrings
Jacob McNamara - Stony Brook University
As originally argued by Coleman, any breakdown of factorization arising from Euclidean wormholes may be reinterpreted as the result of having averaged over a hidden ensemble of theories. By directly categorifying Coleman's argument, we show that any breakdown of Hilbert space factorization arising… -
A Perturbative Window into Asymptotic Safety
Yannick Kluth - University of Toronto
Asymptotic safety offers a compelling UV completion of quantum gravity through a non-trivial UV fixed point. Evidence for this has so far come predominantly from the functional renormalization group. In this talk, I explore a complementary perturbative approach, which offers manifest gauge… -
Emergent time and more from wavefunction collapse in general relativity
Sung-Sik Lee - McMaster University
This talk is about the proposal that (1) quantum states that violate the momentum and Hamiltonian constraints represent instances of time, and (2) time evolution corresponds to the gradual collapse of an initial state toward a diffeomorphism-invariant state, driven by stochastic fluctuations of the… -
Null Musings
Luca Ciambelli - Perimeter Institute for Theoretical Physics
One of the main achievements of my last four years at Perimeter has been the development and formulation of intrinsic null geometry. This framework has served as a common denominator for the study of the (algebraic) quantization of gravity on null hypersurfaces; connections to quantum-gravity… -
Canonical Quantization of Singular Configuration Spaces: Symmetry Reduction, Mass Gap Bounds, and Non-smooth Calculus
Luca Mrini - University of Vienna
In this work-in-progress, we study the quantization of singular configuration spaces, generalizing the canonical structures of smooth quantum mechanics. We develop a framework for constructing a Hilbert space of quantum states, generalized position and momentum operators, a kinetic-plus-potential… -
Quantum Geometry of the Light Cone
Wolfgang Wieland - University of Erlangen-Nuremberg
In Einstein's theory of general relativity, the causal structure of spacetime is itself dynamical. Causality is encoded into the geometry of light cones that bend under the influence of gravity. Quantum theory, on the other hand, tells us that nature is intrinsically probabilistic. A sharply defined… -
Mixed-helicity sector of celestial symmetries and the shadow transform
Domenico Giuseppe Salluce - University of Udine
The asymptotic symmetries of null infinity in asymptotically flat spacetimes can be enhanced to a w1+∞ algebra, when restricting to a single graviton helicity sector. These symmetries were first extracted from the operator product expansion (OPE) of conformal gravitons in celestial holography. They… -
The semiclassical energy outflux emerging from a collapsing shell
Noa Zilberman - Princeton
When a compact object collapses to form a black hole, quantum field theory predicts the emission of an energy outflux to future null infinity, which later relaxes to Hawking radiation. Within the semiclassical framework, we derive a simple, closed form, analytical expression for the energy outflux… -
Spectral Density of the Causal Propagator
Yasaman Kouchekzadeh Yazdi - Dublin Institute For Advanced Studies
In scalar quantum field theory, the causal propagator, which is proportional to the spacetime commutator of the field, plays an essential role. I will discuss some ways the causal propagator and its spectrum have been used to formulate quantum field theory in a more explicitly covariant manner in… -
An algebra of proper observables at null infinity: Dirac brackets, Memory and Goldstone probes
Rodrigo Andrade E Silva - Perimeter Institute for Theoretical Physics
The gravitational memory problem is typically phrased in terms of the failure of constructing a (separable) Hilbert space for radiative gravitational modes at null infinity containing distinct memory states. There is, in a sense, a classical version of this problem: so far, there is no completely… -
The gravitational S-matrix from the path integral: asymptotic symmetries and soft theorems
The classical action, or more generally the path integral, is a convenient framework for extracting the physical consequences of symmetries. In recent years, new symmetries of gravity in asymptotically flat spacetime have been uncovered based on relations to soft theorems governing the S-matrix. I… -
Can a multiverse theory explain the H_0 tension, the S_8 tension, the w(z) < -1 behavior and many other cosmological observations? Maybe!
Jan Ambjorn - University of Copenhagen
A simple multiverse model explains the late time exponential expansion of our universe without the need of a cosmological constant. Assuming that the local measurement of H_0 is correct, it also give a better fit to data than the standard LCDM model, as well as a z-dependent state parameter w(z)…