More Like this

1. Interactions and Dynamics of One-Dimensional Droplets, Bubbles and Kinks

   https://doi.org/10.3390/condmat8030067  

   Katsimiga, Garyfallia C.; Mistakidis, Simeon I.; Malomed, Boris A.; Frantzeskakis, Dimitris J.; Carretero-Gonzalez, Ricardo; Kevrekidis, Panayotis G. (September 2023, Condensed Matter)

   We explore the dynamics and interactions of multiple bright droplets and bubbles, as well as the interactions of kinks with droplets and with antikinks, in the extended one-dimensional Gross–Pitaevskii model including the Lee–Huang–Yang correction. Existence regions are identified for the one-dimensional droplets and bubbles in terms of their chemical potential, verifying the stability of the droplets and exposing the instability of the bubbles. The limiting case of the droplet family is a stable kink. The interactions between droplets demonstrate in-phase (out-of-phase) attraction (repulsion), with the so-called Manton’s method explicating the observed dynamical response, and mixed behavior for intermediate values of the phase shift. Droplets bearing different chemical potentials experience mass-exchange phenomena. Individual bubbles exhibit core expansion and mutual attraction prior to their destabilization. Droplets interacting with kinks are absorbed by them, a process accompanied by the emission of dispersive shock waves and gray solitons. Kink–antikink interactions are repulsive, generating counter-propagating shock waves. Our findings reveal dynamical features of droplets and kinks that can be detected in current experiments. 

   more » « less
2. On the Fractional Dynamics of Kinks in Sine-Gordon Models

   https://doi.org/10.3390/math13020220  

   Bountis, Tassos; Cantisán, Julia; Cuevas-Maraver, Jesús; Macías-Díaz, Jorge Eduardo; Kevrekidis, Panayotis G (January 2025, Mathematics)

   In the present work, we explored the dynamics of single kinks, kink–anti-kink pairs and bound states in the prototypical fractional Klein–Gordon example of the sine-Gordon equation. In particular, we modified the order β of the temporal derivative to that of a Caputo fractional type and found that, for 1<β<2, this imposes a dissipative dynamical behavior on the coherent structures. We also examined the variation of a fractional Riesz order α on the spatial derivative. Here, depending on whether this order was below or above the harmonic value α=2, we found, respectively, monotonically attracting kinks, or non-monotonic and potentially attracting or repelling kinks, with a saddle equilibrium separating the two. Finally, we also explored the interplay of the two derivatives, when both Caputo temporal and Riesz spatial derivatives are involved. 

   more » « less
3. C. elegans enteric motor neurons fire synchronized action potentials underlying the defecation motor program

   https://doi.org/10.1038/s41467-022-30452-y  

   Jiang, Jingyuan; Su, Yifan; Zhang, Ruilin; Li, Haiwen; Tao, Louis; Liu, Qiang (May 2022, Nature Communications)

   Abstract C. elegansneurons were thought to be non-spiking until our recent discovery of action potentials in the sensory neuron AWA; however, the extent to which theC. elegansnervous system relies on analog or digital coding is unclear. Here we show that the enteric motor neurons AVL and DVB fire synchronous all-or-none calcium-mediated action potentials following the intestinal pacemaker during the rhythmicC. elegansdefecation behavior. AVL fires unusual compound action potentials with each depolarizing calcium spike mediated by UNC-2 followed by a hyperpolarizing potassium spike mediated by a repolarization-activated potassium channel EXP-2. Simultaneous behavior tracking and imaging in free-moving animals suggest that action potentials initiated in AVL propagate along its axon to activate precisely timed DVB action potentials through the INX-1 gap junction. This work identifies a novel circuit of spiking neurons inC. elegansthat uses digital coding for long-distance communication and temporal synchronization underlying reliable behavioral rhythm. 

   more » « less
4. Wormholes with ends of the world

   https://doi.org/10.1007/JHEP09(2025)166  

   Wang, Diandian; Wang, Zhencheng; Wei, Zixia (September 2025, Journal of High Energy Physics)

   A<sc>bstract</sc> We study classical wormhole solutions in 3D gravity with end-of-the-world (EOW) branes, conical defects, kinks, and punctures. These solutions compute statistical averages of an ensemble of boundary conformal field theories (BCFTs) related to universal asymptotics of OPE data extracted from the 2D conformal bootstrap. Conical defects connect BCFT bulk operators; branes join BCFT boundary intervals with identical boundary conditions; kinks (1D defects along branes) link BCFT boundary operators; and punctures (0D defects) are endpoints where conical defects terminate on branes. We provide evidence for a correspondence between the gravity theory and the ensemble. In particular, the agreement of theg-function dependence results from an underlying topological aspect of the on-shell EOW brane action, from which a BCFT analog of the Schlenker-Witten theorem also follows. 

   more » « less
5. A nonlinear journey from structural phase transitions to quantum annealing

   Thudiyangal, M; Kevrekidis, PG; Saxena, A; Bishop, AR (May 2024, Chaos)

   Motivated by an exact mapping between equilibrium properties of a one-dimensional chain of quantum Ising spins in a transverse field (the transverse field Ising (TFI) model) and a two-dimensional classical array of particles in double-well potentials (the “ 4 model”) with weak inter-chain coupling, we explore connections between the driven variants of the two systems. We argue that coupling between the fundamen- tal topological solitary waves in the form of kinks between neighboring chains in the classical  4 system is the analog of the competing effect of the transverse field on spin flips in the quantum TFI model. As an example application, we mimic simplified measurement protocols in a closed quantum model system by studying the classical  phi 4 model subjected to periodic perturbations. This reveals memory/loss of mem- ory and coherence/decoherence regimes, whose quantum analogs are essential in annealing phenomena. In particular, we examine regimes where the topological excitations control the thermal equilibration following perturbations. This paves the way for further explorations of the analogy between lower-dimensional linear quantum and higher-dimensional classical nonlinear systems. 

   more » « less