arXiv subjects

Lorenzo Tranchedone

Publications and source records attributed to Lorenzo Tranchedone.

3 recordsLinked to original sources

arXiv2026

Pre-inflationary QCD axion stars after moduli domination

The growth of adiabatic density perturbations during an era of early matter domination induces $\mathcal{O}(1)$ fluctuations in pre-inflationary QCD axion dark matter across a broad, string-theory-motivated parameter space. Remarkably, at $Λ$CDM matter-radiation equality the scale of these perturbations coincides with the quantum Jeans scale, so they collapse to solitonic ``axion stars''. These axion stars have densities up to $10^4\,\mathrm{eV}^4$, and, including their surrounding halos, they contain as much as $50\%$ of dark matter. Direct searches for a smooth axion background can be suppressed, but transient enhancements or indirect astrophysical signals at axion masses $m_a\lesssim 10^{-5}\,{\rm eV}$ would point to a non-standard cosmological history.

hep-ph↗

arXiv2026

Metastable cosmic strings are broken at the start

We show that metastable cosmic strings break at early times, either via finite-temperature effects or by attaching to pre-existing monopoles during network percolation. The resulting segments can be initially super-horizon in size and thus persist for a significant amount of time. If the strings do not re-percolate, the network's eventual destruction is typically due to this early-time breaking rather than late-time quantum tunnelling. Survival of strings to epochs probed by NANOGrav requires $m_M^2/μ\gtrsim 10^3$, where $m_M$ and $μ$ are the monopole mass and the string tension respectively, over an order of magnitude larger than previous estimates. We also revisit quantum-tunnelling induced breaking. Results from numerical simulations suggest that this occurs mainly at rare high-tension points on the strings, yielding a rate much larger than is usually assumed. We briefly discuss the related scenario of flux tubes in a dark QCD-like hidden sector with dark-quark masses above the confinement scale.

hep-ph↗

arXiv2025

Holographic Generalised Gukov-Witten Defects

Spindle and disc solutions have received significant attention in recent literature. However, it is not entirely clear what these supergravity solutions represent in the dual SCFT. In this work we elucidate this issue by considering a different global completion of the spindle solution, focusing on a single conical defect. We argue that these solutions can be interpreted as the insertion of a single (generalised) Gukov-Witten defect in the bulk SCFT. We give compelling evidence for this claim by uplifting the solutions to type IIB supergravity and showing that the five-dimensional $\frac{1}{2}$-BPS solutions uplifts to the bubbling surface operators solutions. Their less supersymmetric cousins give rise to a large class of holographic generalised Gukov-Witten surface operators for which we perform a detailed geometric analysis. To corroborate these claims we compute a variety of holographic observables such as the renormalised action, stress tensor one-point function and defect entanglement entropy. In addition, we extend the holographic inflow mechanism to account for bulk-to-defect inflow to study the symmetries and anomalies of the bulk and defect.

hep-th↗