arXiv subjects

Cameron Norton

Publications and source records attributed to Cameron Norton.

5 recordsLinked to original sources

arXiv2026

Catastrophic Inflation in the Axiverse

In the landscape of compactifications of type IIB string theory on O3/O7 orientifolds of Calabi--Yau threefolds, we identify regions of the axion potential in specific geometries that support small-field inflation, under the assumption that the overall Calabi--Yau volume can be stabilized at certain tuned values. At the tuned volume multiple critical points of the axion potential merge in a ``catastrophe'', creating a region with small gradient and small Hessian determinant --- necessary conditions for slow-roll inflation. We describe an algorithm that identifies several explicit examples of these catastrophes that have small field range $f / M_{\rm Pl} \ll 1 $ yet inflate for thousands of efolds. Some examples correctly reproduce the observed spectral tilt but not the amplitude of scalar perturbations, while others reproduce the observed amplitude but with a tilt that is slightly too red. All our examples have negligible tensor perturbations and no significant non-Gaussianity generated during the slow-roll phase. Our results demonstrate that string theory axions can be the source of cosmic inflation without alignment or large field ranges, provided that the K\"ahler moduli can be stabilized at special values of the volume.

hep-th↗

arXiv2026

Source-Induced Reflection in Balanced Shallow-Water Networks

Width-balance conditions at a junction are often associated with reflectionless transmission, or transparency, in some one-dimensional wave models on networks. We show that, on cyclic networks, this identification is incomplete: local balance is a vertex-level condition, while transparency also requires synchronization of the path travel times. To make this precise, we consider a shallow-water wave model and derive the channel-width-weighted scattering law for a vertex of arbitrary degree and introduce a source-relative definition of balance, reflecting the fact that the same junction may be reflective or reflectionless depending on which edges carry incoming waves. Under this definition, a balanced vertex is transparent only to the synchronized incoming-amplitude direction. For an $N$-path island, the resulting first-generation upstream reflection is governed in frequency space by the width-weighted distribution of path delays. Exact broadband cancellation requires all path travel times to agree; when they do not, commensurability of the path-length differences produces a periodic comb of frequency-selective zeros, independent of channel widths. At $N\ge 4$ we further exhibit a hybrid regime in which the reflection factor vanishes without commensurability among the path lengths.

nlin.PS↗

arXiv2026

The Life and Death of Stars That Capture Primordial Black Holes

Primordial black holes (PBHs) in the asteroid mass window ($10^{17}-10^{23}\,{\rm g}$) remain viable dark matter candidates and can be captured by stars. We develop the first global framework for the evolution of stars that capture PBHs, combining analytic calculations, stellar evolution models, 3D general-relativistic magnetohydrodynamic simulations, and Monte Carlo population synthesis. We find that the fate of these systems bifurcates: PBHs that form an accretion disk before consuming the host drive explosive disruption, whereas PBHs captured too late or growing too slowly consume the star quietly. Capture is dominated by three-body interactions with planetary or stellar companions. For a solar-type host with a Jupiter analog, inspiral within a main-sequence lifetime requires $M_{\rm BH}^{\rm crit}\gtrsim 10^{22}\,{\rm g}$, while lighter PBHs generally require tighter companions. Once deposited at the center, the PBH grows through inefficient quasi-spherical Bondi accretion; if it reaches the angular-momentum threshold before consuming the host, the inflow circularizes into a disk. Our Monte Carlo calculations yield sizable quiet-consumption and explosive-disruption populations, with final PBH masses $M_{\rm BH}\sim0.01-1\,M_\odot$ and disk-forming PBH spins $a_\ast\approx0.8$. Disk formation is the point of no return: disk winds and relativistic jets of $\sim10^{45}-10^{50}\,{\rm erg\,s^{-1}}$ disrupt the star within minutes. The resulting transients may include a $\sim$day-long UV/blue signal, radio afterglow, and, if the jet escapes, an X-ray-flash/low-luminosity gamma-ray-burst (XRF/llGRB) signal. For an $O(1)$ PBH dark matter fraction and optimistic capture assumptions, the event rate can reach that of llGRBs. The low-mass, high-spin remnants offer a complementary PBH probe and possible source for subsolar BH mergers.

astro-ph.HE↗

arXiv2026

Accretion of Primordial Black Holes in Stellar Interiors

We study spherical accretion onto primordial black holes (PBHs) embedded in the core of a solar-type star. We compute the radiative efficiency self-consistently for the first time across the optically thin range ($10^{-16.5}$-$10^{-10}M_\odot$) with time-dependent simulations, and follow the growth up to $10^{-2}M_\odot$ using an analytical photon-trapping prescription above $5\times 10^{-13}M_\odot$. Near the Schwarzschild radius ($r_{\rm S}\sim 10^{-11}$cm for a $10^{-16}M_\odot$ PBH), gas compressed to $T\sim 10^{11}$K radiates through microphysical processes that fundamentally alter the classical adiabatic Bondi solution. We solve the time-dependent spherical Euler equations with an implicit cooling source term, determining $\dot M$, $\eta = L/\dot M c^2$, and the flow structure self-consistently. We identify three regimes for spherical accretion: a Hot Bondi regime ($M_{\rm BH}\lesssim 10^{-14}M_\odot$) in which bremsstrahlung cooling is dynamically negligible; a bremsstrahlung-cooling regime ($10^{-14}$-$5\times 10^{-13}M_\odot$) driving the flow toward isothermal with $\eta\approx 10^{-2}$; and a photon-trapping regime above $5\times 10^{-13}M_\odot$, in which the Bondi sphere is optically thick and the accretion rate remains close to the Bondi value. Cooling enhances $\dot M$ by a factor of $\sim$2-7, keeping growth super-exponential throughout the spherical regime. The radiative efficiency is an order of magnitude lower than previously assumed, and the critical initial PBH mass required to consume a solar-mass star within a Hubble time is $M_{\rm 0,crit}\sim 10^{-16}M_\odot$.

astro-ph.HE↗

arXiv2026

Tunneling from an oscillating initial state in quantum mechanics

We study the decay of general initial states out of a metastable potential well in quantum mechanics. We provide a closed-form expression for the probability current that tunnels through the barrier in terms of the resonant states into which the initial state can be decomposed. All ingredients in the equation are computed analytically to first subleading order in the semiclassical limit. Specializing to a coherently-oscillating initial state, we derive an approximation to the time-dependent decay rate and demonstrate its accuracy by comparing it to a numerical solution of the Schr\"odinger equation.

quant-ph↗