SciPost Physics

SciPost Physics Vol. 20 issue 2 (February 2026)

Previous issue | Vol. 20 issue 1

• Tachyonic and parametric instabilities in an extended bosonic Josephson junction

  Laura Batini, Sebastian Erne, Jörg Schmiedmayer, Jürgen Berges

  SciPost Phys. 20, 026 (2026) · published 2 February 2026 | Toggle abstract · pdf

  We study the decay of phase coherence in an extended bosonic Josephson junction realized via two tunnel-coupled Bose-Einstein condensates. Specifically, we focus on the $\pi$-trapped state of large population and phase imbalance, which, similar to the breakdown of macroscopic quantum self-trapping, becomes dynamically unstable due to the amplification of quantum fluctuations. We analytically identify early tachyonic and parametric instabilities connected to the excitation of atom pairs from the condensate to higher momentum modes along the extended direction. Furthermore, we perform Truncated Wigner numerical simulations to observe the build-up of non-linearities at later times and explore realistic experimental parameters.

• Asymptotic safety, quantum gravity, and the swampland: A conceptual assessment

  Ivano Basile, Benjamin Knorr, Alessia Platania, Marc Schiffer

  SciPost Phys. 20, 027 (2026) · published 2 February 2026 | Toggle abstract · pdf

  We provide a conceptual assessment of some aspects of fundamental quantum field theories of gravity in light of foundational aspects of the swampland program. On the one hand, asymptotically safe quantum gravity may provide a simple and predictive framework, thanks to a finite number of relevant parameters. On the other hand, a (sub-)set of intertwined swampland conjectures on the consistency of quantum gravity can be argued to be universal via effective field theory considerations. We answer whether some foundational features of these frameworks are compatible. This involves revisiting and refining several arguments (and loopholes) concerning the relation between field-theoretic descriptions of gravity and general swampland ideas. We identify the thermodynamics of black holes, spacetime topology change, and holography as the core aspects of this relation. We draw lessons on the features that a field theoretic description of gravity must (not) have to be consistent with fundamental principles underlying the swampland program, and on the universality of the latter.

• Local zeta functions of multiparameter Calabi-Yau threefolds from the Picard-Fuchs equations

  Philip Candelas, Xenia de la Ossa, Pyry Kuusela

  SciPost Phys. 20, 028 (2026) · published 3 February 2026 | Toggle abstract · pdf

  The deformation approach of arXiv:2104.07816 for computing zeta functions of one-parameter Calabi-Yau threefolds is generalised to cover also multiparameter manifolds. Consideration of the multiparameter case requires the development of an improved formalism. This allows us, among other things, to make progress on some issues left open in previous work, such as the treatment of apparent and conifold singularities and changes of coordinates. We also discuss the efficient numerical computation of the zeta functions. As examples, we compute the zeta functions of the two-parameter mirror octic, a non-symmetric split of the quintic threefold also with two parameters, and the $S_5$ symmetric five-parameter Hulek-Verrill manifolds. These examples allow us to exhibit the several new types of geometries for which our methods make practical computations possible. They also act as consistency checks, as our results reproduce and extend those of [K. Hulek and H. Verrill, Nagoya Math. J. 179, 103 (2005)] and arXiv:math/0304169. To make the methods developed here more approachable, a Mathematica package CY3Zeta for computing the zeta functions of Calabi-Yau threefolds, which is attached to this paper, is presented.

• A strong-weak duality for the 1d long-range Ising model

  Dario Benedetti, Edoardo Lauria, Dalimil Mazac, Philine van Vliet

  SciPost Phys. 20, 029 (2026) · published 3 February 2026 | Toggle abstract · pdf

  We investigate the one-dimensional Ising model with long-range interactions decaying as $1/r^{1+s}$. In the critical regime, for $1/2 ≤ s ≤ 1$, this system realizes a family of nontrivial one-dimensional conformal field theories (CFTs), whose data vary continuously with $s$. For $s>1$ the model has instead no phase transition at finite temperature, as in the short-range case. In the standard field-theoretic description, involving a generalized free field with quartic interactions, the critical model is weakly coupled near $s=1/2$ but strongly coupled in the vicinity of the short-range crossover at $s=1$. We introduce a dual formulation that becomes weakly coupled as $s \to 1$. Precisely at $s=1$, the dual description becomes an exactly solvable conformal boundary condition of the two-dimensional free scalar. We present a detailed study of the dual model and demonstrate its effectiveness by computing perturbatively the CFT data near $s=1$, up to next-to-next-to-leading order in $1-s$, by two independent approaches: (i) standard renormalization of our dual field-theoretic description and (ii) the analytic conformal bootstrap. The two methods yield complete agreement.

• Entanglement and quench dynamics in the thermally perturbed tricritical fixed point

  Csilla Király, Máté Lencsés

  SciPost Phys. 20, 030 (2026) · published 3 February 2026 | Toggle abstract · pdf

  We consider the Blume-Capel model in the scaling limit to realize the thermal perturbation of the tricritical Ising fixed point. We develop a numerical scaling limit extrapolation for one-point functions and Rényi entropies in the ground state. In a mass quench scenario, we found long-lived oscillations despite the absence of explicit spin-flip symmetry breaking or confining potential. We construct form factors of branch-point twist fields in the paramagnetic phase. In the scaling limit of small quenches, we verify form factor predictions for the energy density and leading magnetic field using the dynamics of one-point functions, and branch-point twist fields using the dynamics of Rényi entropies.