The soft sector phase space of asymptotically flat gravity equals the phase space of radial size fluctuations of a finite causal diamond in flat spacetime.
Conformally Soft Photons and Gravitons
6 Pith papers cite this work. Polarity classification is still indexing.
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Pith papers citing it
abstract
The four-dimensional $S$-matrix is reconsidered as a correlator on the celestial sphere at null infinity. Asymptotic particle states can be characterized by the point at which they enter or exit the celestial sphere as well as their $SL(2,\mathbb C)$ Lorentz quantum numbers: namely their conformal scaling dimension and spin $h\pm \bar h$ instead of the energy and momentum. This characterization precludes the notion of a soft particle whose energy is taken to zero. We propose it should be replaced by the notion of a conformally soft particle with $h=0$ or $\bar h=0$. For photons we explicitly construct conformally soft $SL(2,\mathbb C)$ currents with dimensions $(1,0)$ and identify them with the generator of a $U(1)$ Kac-Moody symmetry on the celestial sphere. For gravity the generator of celestial conformal symmetry is constructed from a $(2,0)$ $SL(2,\mathbb C)$ primary wavefunction. Interestingly, BMS supertranslations are generated by a spin-one weight $(\frac{3}{2},\frac{1}{2})$ operator, which nevertheless shares holomorphic characteristics of a conformally soft operator. This is because the right hand side of its OPE with a weight $(h,\bar h)$ operator ${\cal O}_{h,\bar h}$ involves the shifted operator ${\cal O}_{h+\frac{1}{2},\bar h+ \frac{1}{2}}$. This OPE relation looks quite unusual from the celestial CFT$_2$ perspective but is equivalent to the leading soft graviton theorem and may usefully constrain celestial correlators in quantum gravity.
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A 3d sourced conformal Carrollian field theory is proposed to holographically capture 4d flat gravity kinematics, with Ward identities matching 2d celestial CFT after relating operators.
Restricting one helicity to the wedge sector and introducing shadow charges yields closed mixed-helicity algebras for all spins in gravity and gauge theory, plus dual mass BMS extensions and non-vanishing electromagnetic central charges.
A Carrollian theory on null infinity reproduces all MHV and NMHV Yang-Mills tree amplitudes, with a new explicit NMHV expression.
Higher spin particles generate w_∞ and S-algebra subalgebras inside the soft holographic symmetry algebra that do not commute with the graviton and gluon versions.
A review summarizing Carrollian symmetries, CCFT constructions, and applications in AFS holography, Carroll hydrodynamics, and condensed matter phenomena such as fractons and flat bands.
citing papers explorer
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From Asymptotically Flat Gravity to Finite Causal Diamonds
The soft sector phase space of asymptotically flat gravity equals the phase space of radial size fluctuations of a finite causal diamond in flat spacetime.
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Carrollian Perspective on Celestial Holography
A 3d sourced conformal Carrollian field theory is proposed to holographically capture 4d flat gravity kinematics, with Ward identities matching 2d celestial CFT after relating operators.
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Mixed-helicity bracket of celestial symmetries
Restricting one helicity to the wedge sector and introducing shadow charges yields closed mixed-helicity algebras for all spins in gravity and gauge theory, plus dual mass BMS extensions and non-vanishing electromagnetic central charges.
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Towards a Carrollian Description of Yang-Mills
A Carrollian theory on null infinity reproduces all MHV and NMHV Yang-Mills tree amplitudes, with a new explicit NMHV expression.
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Note on higher spins and holographic symmetry algebra
Higher spin particles generate w_∞ and S-algebra subalgebras inside the soft holographic symmetry algebra that do not commute with the graviton and gluon versions.
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The Carrollian Kaleidoscope
A review summarizing Carrollian symmetries, CCFT constructions, and applications in AFS holography, Carroll hydrodynamics, and condensed matter phenomena such as fractons and flat bands.