Quantum Gravity

A formal quantization of four-dimensional gravity coupled to a massless scalar field is completed in loop quantum gravity, with the scalar field serving as internal time and a physical Hamiltonian generating evolution.

arxiv:1009.2445 · gr-qc · 2010-09

Replacing constant gravitational vertex couplings with entire functions of momentum is claimed to render quantum gravity ultraviolet finite, and a context-dependent choice of vertex energy scale is claimed to suppress the cosmological constant.

arxiv:1008.2482 · gr-qc · 2010-08

Biographical memoir celebrating the life and works of theoretical physicist Stanley Deser.

arxiv:2611.11323 · hep-th · 2026-11

Numerical models confirm that small corrections to Hawking emission cannot remove the radiation's entanglement with the hole; only order-unity horizon modifications can.

arxiv:1101.4899 · hep-th · 2011-01

Minimal Flavor Violation, the rule that new physics couples to quarks only through the Standard Model Yukawa matrices, automatically stabilizes the lightest state of many flavor multiplets, giving a new class of dark matter candidates.

arxiv:1105.1781 · hep-ph · 2011-05

Gravitationally enhanced friction inflation reduces to single-field inflation with standard consistency relations, and its local non-Gaussianity is dominated by the gauge transformation from flat to uniform-field slicing.

arxiv:1106.0502 · astro-ph.CO · 2011-06

Requiring exact, spontaneously broken local conformal invariance in a gravity-coupled particle theory would fix all its parameters at a zero of the beta functions, though no explicit model is built.

arxiv:1104.4543 · gr-qc · 2011-04

A global U(1)_{B-L} broken at the TeV scale can generate Zee-Babu two-loop neutrino masses and stabilize a Dirac dark matter particle via a remnant Z_2 symmetry.

arxiv:1105.4626 · hep-ph · 2011-05

The lectures argue that unitarity in black hole evaporation requires new, nearly local physics beyond quantum field theory, and that the gravitational S-matrix is a sharp probe of that regime.

arxiv:1105.2036 · hep-th · 2011-05

Treating the number of horizon punctures as a thermodynamic variable with a chemical potential yields black hole entropy equal to one quarter the horizon area for all values of the Immirzi parameter.

arxiv:1107.1320 · gr-qc · 2011-07

The information paradox survives every proposed resolution except the fuzzball construction, which removes the horizon the paradox depends on.

arxiv:1108.0302 · hep-th · 2011-08

Replacing the tetrad with a fermion bilinear and discretizing on a hypercubic lattice yields a finite path integral for quantum gravity, though the continuum limit is not demonstrated.

arxiv:1109.0091 · hep-th · 2011-09

A four-pulse optomechanical sequence maps the commutator of a massive mechanical oscillator onto an optical phase shift, enabling a tabletop test of Planck-scale commutator deformations.

arxiv:1111.1979 · quant-ph · 2011-11

Black hole unitarity can be restored by treating Hilbert-space tensor factorization, not spacetime, as fundamental, with information transferred from the black hole interior to an exterior atmosphere through minimal subspace-transfer maps.

arxiv:1201.1037 · hep-th · 2012-01

A coarse graining scheme with dynamics-selected embedding maps produces fixed point Hamilton's principal functions for a 2D scalar field, but the quantum extension with the standard loop quantum gravity embedding does not reproduce the classical limit.

arxiv:1205.6127 · gr-qc · 2012-05

A classical solution of the Lorentzian IIB matrix model gives a scale factor whose equation-of-state parameter drifts from -1 to -1/3, offered as a dynamical explanation for the smallness of the cosmological constant.

arxiv:1208.0711 · hep-th · 2012-08

No narrow dijet resonances or quantum black holes appear in 5 fb^-1 of 7 TeV CMS data; 95% CL upper limits exclude string resonances below 4.31 TeV, excited quarks below 3.32 TeV, and several other models, with a new b-tagged channel constraining b-quark-preferring resonances.

arxiv:1210.2387 · hep-ex · 2012-10

In a fixed-reference-frame quantum gravity framework, an evaporating black hole drifts into a superposition of macroscopically different geometries, and the horizon firewall requires exponentially fine-tuned initial conditions.

arxiv:1210.6348 · hep-th · 2012-10

Within a single-coupling Einstein-Hilbert truncation, unimodular gravity has an ultraviolet-attractive interacting fixed point at G* = 0.876 with critical exponent 3.878, distinct from the standard asymptotic-safety fixed point.

arxiv:1301.0879 · gr-qc · 2013-01

A source term confined to the black hole atmosphere can transfer information outward without a horizon singularity, and high-angular-momentum couplings let information flow track the enhanced energy flux of a string-mined black hole.

arxiv:1302.2613 · hep-th · 2013-02

Space and time may be a condensate emerging from a phase transition of discrete pre-geometric quantum building blocks, and group field theory offers a tentative route to deriving cosmology from that condensate.

arxiv:1302.2849 · physics.hist-ph · 2013-02

Spherical Rindler space, the exterior of a sphere in flat space as seen by radially accelerating observers, has gravitational entropy equal to one quarter of the horizon area, consistent with an entanglement interpretation.

arxiv:1305.0856 · hep-th · 2013-05

No energy-dependent speed of light is found in four bright Fermi gamma-ray bursts; the 95% limits place the linear Lorentz-violation scale above 7.6 Planck energies for GRB 090510, and above about 2 Planck energies under the paper's most conservative treatment.

arxiv:1305.3463 · astro-ph.HE · 2013-05

A quantum-gravity-inspired effective density halts homogeneous dust and radiation collapse at a critical density, producing a bounce and, the authors argue, no event horizon.

arxiv:1305.4790 · gr-qc · 2013-05

Perturbative quantum gravity is constructed as a locally covariant, background-independent effective field theory, with diffeomorphism-invariant observables defined via metric-dependent coordinates.

arxiv:1306.1058 · math-ph · 2013-06

An anomaly-free gauged discrete R symmetry can shield the Peccei-Quinn symmetry from quantum-gravity breaking, yielding a large family of viable axion models once the MSSM is extended by vector-like quarks and singlet fields.

arxiv:1308.1227 · hep-ph · 2013-08

By dressing asymptotic states with coherent clouds of soft gravitons, the authors define an infrared-finite S matrix for perturbative quantum gravity and show soft divergences cancel to all orders in gravitational potential scattering.

arxiv:1308.6285 · hep-th · 2013-08

A heavy sector that decouples from the Standard Model as its mixing couplings vanish is protected by an enhanced Poincaré symmetry, making a light Higgs technically natural without new TeV-scale particles.

arxiv:1310.0223 · hep-ph · 2013-10

Monte Carlo simulation of the D0-brane matrix quantum mechanics at N = 3, 4, 5 reproduces the leading 1/N^2 quantum gravity correction to the dual black hole energy, 7.41 T^2.8 - 5.77 T^0.4 / N^2.

arxiv:1311.5607 · hep-th · 2013-11

Quantum-gravity corrections to cosmological perturbations close into a deformed constraint algebra whose deformation function turns negative near the bounce density, implying a change of space-time signature rather than a mere instability.

arxiv:1404.1018 · gr-qc · 2014-04

Spontaneously broken global scale invariance supplies a shift symmetry that protects the inflaton potential, reproducing Starobinsky-like and axion-like large-field inflation from small explicit breaking by nearly marginal operators.

arxiv:1406.5192 · hep-th · 2014-06

Localization of the four-dimensional gauged supergravity path integral on AdS4 reduces to a two-variable integral whose saddle-point evaluation reproduces the ABJM Airy function, assuming a flat measure and ignoring a known shift in the rank.

arxiv:1406.0505 · hep-th · 2014-06

Replacing the Kerr mass with an exponentially suppressed mass function gives a rotating metric whose curvature invariants stay finite at the ring while matching Kerr-Newman at large radius.

arxiv:1408.5668 · gr-qc · 2014-08

The tree-order scalar and tensor power spectra from inflation carry explicit factors of the gravitational coupling and are therefore the first observed quantum gravitational effects, a claim the author uses to argue quantum gravity has become an empirical discipline.

arxiv:1407.4748 · gr-qc · 2014-07

Group field theory reformulates loop quantum gravity as a quantum field theory of spin network vertices, giving spin foam models a generating functional and a route to continuum and cosmological limits.

arxiv:1408.7112 · gr-qc · 2014-08

A renormalization-group improved higher-derivative gravity model yields an unstable de Sitter inflation whose spectral index can be brought into agreement with Planck data by tuning a Gauss-Bonnet coupling.

arxiv:1412.1073 · gr-qc · 2014-12

Quantum cosmology is reframed as a many-patch, condensed-matter-like problem rather than a minisuperspace quantization of the entire universe.

arxiv:1501.04899 · gr-qc · 2015-01

The exponential non-local gravity that avoids massive ghosts at tree level is argued to acquire infinitely many complex ghost poles from quantum corrections.

arxiv:1502.00106 · hep-th · 2015-01

Gravitationally dressed operators fail to commute at spacelike separation, so quantum gravity has no exact net of local commuting subalgebras and entanglement cannot play a fundamental role.

arxiv:1503.08207 · hep-th · 2015-03

A general recurrence relation for the effective axion decay constant in N-axion models shows power-law and exponential enhancement regimes, and implies that stopping this enhancement at large N requires an enormous, possibly exponential, number of dominant instanton terms.

arxiv:1504.03566 · hep-th · 2015-04

Tensor-invariant bubble interactions supply group field theories with enough locality to renormalize, yielding a classified table of power-counting renormalizable models and hints of Wilson-Fisher-like fixed points.

arxiv:1603.01902 · gr-qc · 2016-03

A numerical global scaling solution for dilaton quantum gravity exists for one particular value of a free kinetic ratio, and its Einstein-frame potential has a maximum that could in principle support inflation but does not end it.

arxiv:1605.01858 · hep-th · 2016-05

Explicit two-gauge-field models show that Higgsing a Weak-Gravity-Conjecture-satisfying theory produces low-energy gauge forces that violate the conjecture, so it cannot veto effective field theories.

arxiv:1608.06951 · hep-th · 2016-08

Under asymptotically safe gravity the fermion mass stays a relevant coupling, so chiral symmetry is not restored in the infrared and must be an exact microscopic symmetry of the theory.

arxiv:1611.05878 · gr-qc · 2016-11

Echoes from reflecting walls around compact objects do not track quasi-normal frequencies and change shape from bounce to bounce, and naive Dirichlet conditions on the Teukolsky variable do not model a local reflecting wall.

arxiv:1702.04833 · gr-qc · 2017-02

Loop quantum gravity's discrete quantum geometry can reproduce the Bekenstein-Hawking area law and frame black hole evaporation as information degradation rather than loss, though the program remains incomplete.

arxiv:1703.09149 · gr-qc · 2017-03

A family of mimetic higher-derivative scalar-tensor theories reproduces the loop quantum cosmology effective Friedmann dynamics for flat, closed, and open isotropic universes.

arxiv:1703.10812 · gr-qc · 2017-03

Multiple quantum gravity programs independently suggest that spacetime's effective dimension falls toward two at the Planck scale, though no approach yet proves it.

arxiv:1705.05417 · gr-qc · 2017-05

By tuning the area assigned to quantization loops as a function of black hole mass, the loop-quantized Schwarzschild interior can be made to produce a symmetric black-to-white hole bounce with equal masses.

arxiv:1707.07333 · gr-qc · 2017-07

An extended Weak Gravity Conjecture with scalar fields can force a charged particle's mass arbitrarily far below the theory's ultraviolet cutoff, a form of hierarchical UV/IR mixing.

arxiv:1709.01790 · hep-th · 2017-09

Global symmetries in particle physics are approximate consequences of gauge symmetry, and in a world with quantum gravity every exact symmetry is a gauge symmetry.

arxiv:1710.01791 · hep-th · 2017-10

A 2N-field Gaussian boundary model is proposed as the exact Hilbert space of minimal higher spin de Sitter gravity, reproducing the earlier Sp(N) proposal at large N and yielding closed-form late-time correlators.

arxiv:1711.10037 · hep-th · 2017-11

Extending the Fourier-transform treatment of double-trace deformations from scalars and vectors to the metric, the authors argue the T Tbar deformation's holographic cutoff surface should carry a Neumann, not Dirichlet, boundary condition.

arxiv:1801.09708 · hep-th · 2018-01

A thin-shell gravastar with both noncommutative and Kazakov-Solodukhin deformations is constructed, and higher-order optical effects are shown to break the leading-order degeneracy between the two scales.

arxiv:2611.07183 · gr-qc · 2026-11

Graviton detection via resonant absorption in macroscopic quantum acoustic resonators is a realistic experimental goal.

arxiv:2611.07447 · gr-qc · 2026-11

A Gaussian-localized holonomy profile in covariant loop quantum black holes gives a geometric realization of the bump effect, including overtone overtaking and a deviation-time observation window for scalar ringing.

arxiv:2611.03902 · gr-qc · 2026-11

Standard effective field theory justifies adding non-perturbative terms to no-scale supergravities, so the perturbative runaway does not invalidate KKLT-type de Sitter constructions.

arxiv:1808.08971 · hep-th · 2018-08

A chiral confining SU(5) sector makes the Peccei-Quinn symmetry automatic and pushes PQ-violating Planck operators up to dimension nine.

arxiv:1812.08174 · hep-ph · 2018-12

In asymptotically safe gravity the Higgs quartic coupling is an irrelevant parameter at the UV fixed point, making the Higgs mass predictable, and for strong enough gravity the mass term is also irrelevant, explaining the gauge hierarchy.

arxiv:1811.11706 · hep-th · 2018-11

Tensor networks give a compact, entanglement-controlled representation of complex quantum many-body states, and this review maps their structures, algorithms, and claimed reach into quantum gravity and machine learning.

arxiv:1812.04011 · cond-mat.str-el · 2018-12

The Gibbons-Hawking entropy of de Sitter space is derived as the holographic entanglement entropy between its past and future conformal boundaries, and the bulk entanglement between its two Rindler wedges is computed to be twice that value.

arxiv:1901.04554 · hep-th · 2019-01

Exact bulk correlation functions in JT gravity, computed in a boundary-defined radar frame, show that quantum gravity effects dominate near the horizon and invalidate the semiclassical matter-on-curved-spacetime approximation there.

arxiv:1902.11194 · hep-th · 2019-02

A holographic model predicts interferometer arm-length fluctuations of order sqrt(Planck length times arm length), with transverse correlations strong enough to make the signal observable.

arxiv:1902.08207 · gr-qc · 2019-02

A conjectured inequality on scalar potentials, requiring scalar self-interactions to beat gravity, reproduces the axion weak gravity bound, predicts an emergent circle, and constrains inflation and neutrino masses.

arxiv:1903.08878 · hep-th · 2019-03

Demanding that quantum gravity solve the Standard Model's Landau-pole problems restricts the viable parameter space of unimodular, Weyl-squared, and asymptotically safe gravity, with Weyl-squared results shown to be regulator-, parameterization-, and gauge-independent at leading order.

arxiv:1907.11173 · hep-th · 2019-07

Assuming wormhole volume equals CFT circuit complexity, the authors argue that either the AdS/CFT dictionary is exponentially complex or the quantum Church-Turing thesis fails in quantum gravity.

arxiv:1910.14646 · quant-ph · 2019-10

The finite-N Schur index of N=4 U(N) SYM is reproduced as a sum over wrapped D3-brane contributions, verified numerically through order q^{19+N} for N=1,2,3,4 and matching the Bourdier-Drukker-Felix analytic result in the u to 1 limit.

arxiv:2001.11667 · hep-th · 2020-01

A new swampland conjecture ties the order of a discrete gauge symmetry to the weakness of continuous gauge couplings, and a refined AdS distance conjecture accounts for parametric scale separation in type IIA flux vacua.

arxiv:2003.09740 · hep-th · 2020-03

Exact vanishing of supersymmetric protected quantities in quantum gravity occurs only when the theory is an orbifold of a higher-supersymmetry theory, motivating a new Swampland conjecture.

arxiv:2003.10452 · hep-th · 2020-03

Invisible two-body neutrino decays into a light sterile state and a Goldstone boson can relax the Planck neutrino mass bound from 0.12 eV to about 1 eV, and a simple type-I seesaw extension realizes the required couplings.

arxiv:2007.04994 · hep-ph · 2020-07

Within the DS/dS correspondence, a bulk shock wave in de Sitter space yields a scrambling time and correlator growth rate that saturate the Sekino-Susskind and Maldacena-Shenker-Stanford bounds, with the correlator growing rather than decaying.

arxiv:2005.00021 · hep-th · 2020-04

A hand-picked set of form factors in the quantum effective action yields gravity-mediated scalar scattering amplitudes that are bounded, causal, and scale-free at trans-Planckian energy, without string theory or massive higher-spin states.

arxiv:2007.00733 · hep-th · 2020-07

Adding non-minimal couplings of the Higgs to the Holst and Nieh-Yan terms widens the predicted spectral index and tensor-to-scalar ratio of Higgs inflation to nearly the full range upcoming CMB experiments will probe.

arxiv:2007.12595 · astro-ph.CO · 2020-07

The Kazakov-Solodukhin quantum-corrected Schwarzschild black hole reverses the universal inequality 3/2 r_0 <= r_ph <= b_c/sqrt(3) <= 3M and produces a larger lensing ring than Schwarzschild.

arxiv:2008.00657 · gr-qc · 2020-08

The Swampland Distance Conjecture can be recast as a convex hull condition on tower scalar charge-to-mass ratios, which bounds how non-geodesic a light-field trajectory may be.

arxiv:2012.00034 · hep-th · 2020-11

Requiring that bounds on particle masses and scalar potential slopes be preserved under dimensional reduction singles out specific order-one coefficients, including a mass bound m less than about the d-th root of the cosmological constant that is numerically close to the neutrino mass.

arxiv:2101.11617 · hep-th · 2021-01

A rotating, non-singular loop-quantum-gravity black hole built with the Newman-Janis algorithm has a shadow whose size, compared to M87*, disfavors its horizonless wormhole branch and requires a small quantum parameter.

arxiv:2012.08785 · gr-qc · 2020-12

A Lorentzian version of the effective spin foam path integral is constructed and numerically probed, showing a semi-classical regime for small Barbero-Immirzi parameter on simple triangulations with one bulk triangle.

arxiv:2104.00485 · gr-qc · 2021-04

Vanishing gravitino mass sits at infinite distance in moduli space, forcing a tower of states with mass scaling as m_{3/2}^delta where delta is bounded below by 1/3 for Calabi-Yau threefolds and 1/4 for fourfolds.

arxiv:2104.10181 · hep-th · 2021-04

A new swampland conjecture ties vanishing gravitino mass to an infinite light tower, and in N=2 supergravity the gravitino mass is shown to track the abelian gauge coupling.

arxiv:2104.08288 · hep-th · 2021-04

Fourth-order gravity in the asymptotic-safety program has a non-perturbative fixed point, and the Euler-characteristic coupling flows to positive infinity, favoring spacetimes with negative Euler characteristic.

arxiv:2104.11336 · hep-th · 2021-04

The split property of quantum field theory fails in gravity, and this failure, not any new horizon dynamics, is what resolves Hawking's information paradox and dissolves the monogamy and Page-curve puzzles.

arxiv:2110.05470 · hep-th · 2021-10

A multi-parameter entropy formula contains six known entropies as limits and, when inserted into holographic cosmology, can be tuned to reproduce either the dark energy or the inflation energy scale.

arxiv:2201.02424 · gr-qc · 2022-01

Finiteness of black hole entropy and of quantum gravity amplitudes is argued to imply the Weak Gravity Conjecture, the Distance Conjecture, and a finite number of consistent vacua.

arxiv:2111.00015 · hep-th · 2021-10

Gravity-induced entanglement is shown to arise from a quantum superposition of retarded, causal field configurations, so no entanglement forms when the masses' superpositions are spacelike separated.

arxiv:2202.03368 · quant-ph · 2022-02

A single four-parameter entropy function, fed through horizon thermodynamics, is claimed to produce both a Planck-compatible inflationary era with an exit and a Planck-compatible late-time dark energy equation of state.

arxiv:2205.08876 · gr-qc · 2022-05

A T^2-deformed CFT partition function on a bulk Cauchy slice is proposed to equal a Wheeler-DeWitt wavefunction, giving an explicit map between bulk canonical quantum gravity states and boundary CFT states.

arxiv:2204.00591 · hep-th · 2022-04

A slowly varying positive scalar potential can only extend over a field range bounded by sqrt((d-1)(d-2)) log(1/V) plus a negative order-one constant, derived from the species scale and checked in three string compactification examples.

arxiv:2305.07701 · hep-th · 2023-05

A community survey argues that infinite-dimensional higher spin symmetry may make quantum gravity tractable, and lays out the open problems and mathematical tools of the program.

arxiv:2205.01567 · hep-th · 2022-05

Sgr A*'s measured shadow diameter and deviation from the Schwarzschild prediction bound the loop-quantum-gravity deviation parameter to L_q < 0.042 and < 0.082 in two rotating black hole models.

arxiv:2209.12584 · gr-qc · 2022-09

The Covariant Entropy Bound applied to dynamical-cobordism running solutions yields a bottom-up derivation of the Swampland Distance Conjecture and a convex-hull bound on the species scale decay rate, verified in M-theory torus compactifications.

arxiv:2306.16450 · hep-th · 2023-06

Loop quantum gravity can resolve black hole singularities, but only some quantization choices yield a physically sensible quantum-extended spacetime, according to this review.

arxiv:2301.01309 · gr-qc · 2023-01

Asymptotically safe gravity may UV-complete the Standard Model and predict some of its couplings, but the evidence rests on truncated functional renormalization group calculations.

arxiv:2212.07456 · hep-th · 2022-12

Using exactly known R4 and R2 coefficients in 5 to 10 dimensions, the authors locate desert points, compute moduli-space diameters, and argue the species scale obeys |grad Lambda_s|^2/Lambda_s^2 <= 1/(d-2) everywhere once running from states already in the EFT is subtracted.

arxiv:2310.07213 · hep-th · 2023-10

The paper proposes that the field-space gradients of the lightest tower mass and the species scale have a fixed dot product equal to 1/(d-2), checked in Kaluza-Klein and string toy models but not derived from first principles.

arxiv:2311.01501 · hep-th · 2023-11

The paper lays out a community roadmap for testing quantum gravity with gamma rays, neutrinos, cosmic rays, and gravitational waves, and argues that dedicated experiments, better astrophysical modelling, and open data are required.

arxiv:2312.00409 · gr-qc · 2023-12

Small instantons that generate much of the up-quark Yukawa can suppress the QCD axion mass, allowing it to lie far below the standard QCD axion band.

arxiv:2610.40629 · hep-ph · 2026-10

Requiring an observer's worldline to connect bra to ket in the gravitational path integral enlarges the closed-universe Hilbert space from one dimension to exp(1/G_N) and pushes non-perturbative breakdown for an infalling observer out to exponential times.

arxiv:2501.02632 · hep-th · 2025-01

Planck-scale global-symmetry-violating operators generically shift the axion potential minimum away from zero, so the Peccei-Quinn mechanism works only if their couplings are exponentially small or their phases are coincidentally aligned.

arxiv:hep-th/9202003 · hep-th · 1992-02

Every proposed resolution of black hole information loss, whether information escapes in Hawking radiation, hides in remnants, or leaks out at the end, requires a drastic revision of accepted physics.

arxiv:hep-th/9209058 · hep-th · 1992-09