Bulletin of the American Physical Society
APS April Meeting 2017
Volume 62, Number 1
Saturday–Tuesday, January 28–31, 2017; Washington, DC
Session M6: Quantum Aspects of Gravitation 
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Sponsoring Units: DGRAV Chair: Eugenio Bianchi, Pennsylvania State University Room: Virginia C 
Sunday, January 29, 2017 3:30PM  3:42PM 
M6.00001: Black hole entropy from conformal symmetry on the horizon Steven Carlip The idea that black hole entropy might be governed by a conformal symmetry is an old one, but until now most efforts have focused on either asymptotic symmetries or symmetries on a ``stretched horizon.’’ For twodimensional dilaton gravity, I show the existence of a wellbehaved conformal symmetry that is \emph{on} the horizon, with a central charge that correctly determines the black hole entropy. [Preview Abstract] 
Sunday, January 29, 2017 3:42PM  3:54PM 
M6.00002: Entropy of local smeared field observables Alejandro Satz We reconceptualize the usual entanglement entropy of quantum fields in a spatial region as a limiting case of a more general and welldefined quantity, the entropy of a subalgebra of smeared field observables. We introduce this notion, discuss various examples, and recover from it the area law for the entanglement entropy of a sphere in Minkowski space. [Preview Abstract] 

M6.00003: ABSTRACT WITHDRAWN 
Sunday, January 29, 2017 4:06PM  4:18PM 
M6.00004: Hawking radiation from a collapsing quantum shell Jorge Pullin, Rodrigo Eyheralde, Rodolfo Gambini We study Hawking radiation from a collapsing shell with uncertainty in its position and momentum. We see there are deviations from the usual spectrum early on in the evolution, tending asymptotically to the usual spectrum plus small corrections. [Preview Abstract] 
Sunday, January 29, 2017 4:18PM  4:30PM 
M6.00005: Mechanism of stimulated Hawking radiation in a laboratory BoseEinstein condensate Ted Jacobson, YiHsieh Wang, Mark Edwards, Charles W. Clark Analog black/white hole pairs have been achieved in recent experiments by J. Steinhauer, using an elongated BoseEinstein condensate \footnote{J. Steinhauer, {\em Nature Physics} {\bf 11}, 864 (2014)}. He reported observations of selfamplifying Hawking radiation, via a lasing mechanism operating between the the black and white hole horizons. Through the simulations using the 1D GrossPitaevskii equation, we find that the experimental observations should be attributed not to the black hole laser effect, but rather to a growing zerofrequency bow wave, generated at the whitehole horizon. The relative motion of the black and white hole horizons produces a Doppler shift of the bow wave at the black hole, where it stimulates the emission of monochromatic Hawking radiation. This mechanism is confirmed using temporal and spatial windowed Fourier spectra of the condensate. We also find that shottoshot atom number variations, of the type normally realized in ultracoldatom experiments, and quantum fluctuations of condensates, as computed in the BogoliubovDe Gennes approximation, give densitydensity correlations consistent with those reported in the experiments. In particular, atom number variations can produce a spurious correlation signal. [Preview Abstract] 
Sunday, January 29, 2017 4:30PM  4:42PM 
M6.00006: Projective Perspectives on the Grains of Space in Quantum Gravity Hal Haggard, Simone Speziale Direct quantization of the geometry of space provides an intriguing road towards quantum gravity. Semiclassical investigations of this approach have uncovered dynamical polyhedra as classical models for the discrete quantum grains of space. General mathematical theorems guarantee the existence and uniqueness of these polyhedral grains, but as of yet there has been no way to construct them in general. We discuss the use of projective geometry to directly and analytically construct these grains and the role that this broader symmetry can play in a quantum theory of gravity. [Preview Abstract] 
Sunday, January 29, 2017 4:42PM  4:54PM 
M6.00007: Emergent Rotation from the Planck Scale and the Fermilab Holometer Ohkyung Kwon, Craig Hogan, Jonathan Richardson We present a statistical model of rotational fluctuations of the inertial frame arising from quantum geometry, based on Planck scale information bounds and exact causal symmetry. In an emergent spacetime assembled from noncommuting quantum elements at the Planck scale, in the Minkowskian limit with no dynamics or curvature, quantum correlations are represented by covariant random transverse spatial displacements on light cones. Light that propagates in a nonradial direction inherits a projected component of the rotational correlation that accumulates as a random walk in phase. A calculation of the projection and accumulation leads to exact predictions for statistical signatures in an interferometer of any configuration. Coherent and consistent local inertial frames emerge as observerdependent statistical approximations at large scales, and the crosscovariance for nearly colocated interferometers is shown to depart only slightly from the autocovariance. A specific example computed for the reconfigured secondgeneration Fermilab Holometer shows that the model can be rigorously tested with the sensitivity already achieved in the firstgeneration instrument. [Preview Abstract] 
Sunday, January 29, 2017 4:54PM  5:06PM 
M6.00008: Resolution of quantum singularities Deborah Konkowski, Thomas Helliwell A review of quantum singularities in static and conformally static spacetimes is given. A spacetime is said to be quantum mechanically nonsingular if a quantum wave packet does not feel, in some sense, the presence of a singularity; mathematically, this means that the wave operator is essentially selfadjoint on the space of square integrable functions. Spacetimes with classical mild singularities (quasiregular ones) to spacetimes with classical strong curvature singularities have been tested. Here we discuss the similarities and differences between classical singularities that are healed quantum mechanically and those that are not. Possible extensions of the mathematical technique to more physically realistic spacetimes are discussed. [Preview Abstract] 
Sunday, January 29, 2017 5:06PM  5:18PM 
M6.00009: Emergent Gravity from Vanishing EnergyMomentum Tensor Joshua Erlich We propose a constraint of vanishing energymomentum tensor for quantum gravity. We are led to a metricindependent effective theory similar to the DiracBornInfeld theory with vanishing gauge fields, modulated by a scalar potential. In the limit of a large number of fields, we explicitly demonstrate the existence of a composite massless spin2 graviton in the spectrum that couples to matter as in Einstein gravity. We comment on the cosmological constant problem, the generalization to theories of fermions and gauge fields, and the relation to other approaches to quantum gravity. [Preview Abstract] 
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