arXiv subjects

Anna Biggs

Publications and source records attributed to Anna Biggs.

8 recordsLinked to original sources

arXiv2026

Not all black holes decohere quantum superpositions

We study the decoherence induced by near-extremal charged black holes on quantum systems in their exterior. Specifically, we analyze a thought experiment recently discussed in the literature, where the quantum system is a charged particle prepared in a spatial superposition. Near-extremal black holes are known to exhibit large quantum metric fluctuations of the near-horizon geometry at low temperatures. We show that, at late times, if the black hole is sufficiently close to extremality, these quantum gravity effects make the decoherence rate vanish. This phenomenon is due to a spin-induced energy gap in the quantum black hole spectrum. For energies above the gap, the decoherence rate becomes nonzero, but is still suppressed relative to semiclassical expectations, so these quantum gravity effects always enhance the coherence of the superposition.

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arXiv2026

A melonic quantum mechanical model without disorder

We consider a quantum mechanical model involving interacting fermions without disorder that has the same low energy physics as the supersymmetric SYK model. The model is $SU(2)$ invariant, and the supercharge involves the $ SU(2) $ 3j symbol. We analyze various solvable corners, conceptually explain why it has a melonic expansion, and perform an exact diagonalization for small values of $N$. Expanded around the states with maximal angular momentum, the model is approximated by a two dimensional CFT. The BPS states have a simple description in that regime.

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arXiv2025

Higher-point correlators in the BFSS matrix model

We investigate higher-point correlators in the BFSS matrix model, a non-conformal theory dual to type IIA string theory, using Witten diagrams and techniques from the amplitudes program. While the Witten diagrams are more complex than those relevant for conformal holographic theories, we find that the added complexity is minimal. As an illustration, we compute the leading three-point Witten diagram, evaluating it in a squeezed limit using the method of regions. Our results provide new targets for future Monte-Carlo and quantum simulations of the BFSS matrix model.

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arXiv2025

Following the state of an evaporating charged black hole into the quantum gravity regime

We study the energy probability density function of an evaporating near-extremal charged black hole. At sufficiently low energies, such black holes experience large quantum metric fluctuations in the $AdS_{2}$ throat which are governed by a Schwarzian action. These fluctuations modify Hawking evaporation rates, and therefore also affect how the black hole state evolves over time. In previous work on Schwarzian-corrected Hawking radiation, the black hole was taken to be in the microcanonical or canonical ensemble [arXiv:2411.03447]. However, we find that an initially fixed-energy or fixed-temperature state does not remain so in the regime where Schwarzian corrections are important. We consider three decay channels: the emission of massless scalars, photons, and entangled pairs of photons in angular momentum singlet states. In each of the three cases, we find that in the very low energy, quantum dominated regime, the probability distribution of the black hole energy level occupation tends toward a particular attractor function that effectively depends on only one combination of time and energy. This function is independent of the initial state and gives new predictions for the energy fluxes and Hawking emission spectra of near-extremal charged black holes.

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arXiv2024

Comparing the decoherence effects due to black holes versus ordinary matter

Recently a certain thought experiment was discussed which involves the decoherence of a quantum system due to a black hole. Here we show how this phenomenon is consistent with standard ideas about quantum black holes. In other words, modeling the black hole as a quantum system at finite temperature one obtains the same answer. We demonstrate this by analyzing the problem in terms of an effective theory that can apply both for the black hole case and for an ordinary matter system, showing that the same qualitative effect is present for ordinary matter at finite temperature.

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arXiv2023

A supersymmetric SYK model with a curious low energy behavior

We consider $\mathcal{N}$ = 2, 4 supersymmetric SYK models that have a peculiar low energy behavior, with the entropy going like $S = S_{0} + \text{(constant)}T^{a}$, where $a \neq 1$. The large $N$ equations for these models are a generalization of equations that have been previously studied as an unjustified truncation of the planar diagrams describing the BFSS matrix quantum mechanics or other related matrix models. Here we reanalyze these equations in order to better understand the low energy physics of these models. We find that the scalar fields develop large expectation values which explore the low energy valleys in the potential. The low energy physics is dominated by quadratic fluctuations around these values. These models were previously conjectured to have a spin glass phase. We did not find any evidence for this phase by using the usual diagnostics, such as searching for replica symmetry breaking solutions.

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arXiv2023

Special geometry, quasi-modularity and attractor flow for BPS structures

We study mathematical structures on the moduli spaces of BPS structures of $\mathcal{N}=2$ theories. Guided by the realization of BPS structures within type IIB string theory on non-compact Calabi-Yau threefolds, we develop a notion of BPS variation of Hodge structure which gives rise to special K\"ahler geometry as well as to Picard-Fuchs equations governing the central charges of the BPS structure. We focus our study on cases with complex one dimensional moduli spaces and charge lattices of rank two including Argyres-Douglas $A_2$ as well as Seiberg-Witten $SU(2)$ theories. In these cases the moduli spaces are identified with modular curves and we determine the expressions of the central charges in terms of quasi-modular forms of the corresponding duality groups. We furthermore determine the curves of marginal stability and study the attractor flow in these examples, showing that it provides another way of determining the complete BPS spectrum in these cases.

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arXiv2023

Scaling similarities and quasinormal modes of D0 black hole solutions

We study the gravity solution dual to the D0 brane quantum mechanics, or BFSS matrix model, in the 't Hooft limit. The classical physics described by this gravity solution is invariant under a scaling transformation, which changes the action with a specific critical exponent, sometimes called the hyperscaling violating exponent. We present an argument for this critical exponent from the matrix model side, which leads to an explanation for the peculiar temperature dependence of the entropy in this theory, $S \propto T^{9/5}$. We also present a similar argument for all other $Dp$-brane geometries. We then compute the black hole quasinormal modes. This involves perturbing the finite temperature geometry. These perturbations can be easily obtained by a mathematical trick where we view the solution as the dimensional reduction of an $AdS_{ 2 + 9/5 } \times S^8$ geometry.

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