Publications SISSA
URI permanente per questa collezione
Sfogliare
Immissioni recenti
1 - 5 di 14201
-
PubblicazioneFull Description of Benjamin–Feir Instability for Generalized Korteweg–de Vries Equations( 2025)In this paper we consider a family of generalized Korteweg--de Vries equations and study the linear modulational instability of small amplitude traveling wave solutions. Under explicit nondegeneracy conditions on the dispersion relation, we completely describe the spectrum near the origin of the linearized operator at such solutions and prove that the unstable spectrum (when present) is composed of branches depicting always a closed ``figure 8."" We apply our abstract theorem to several equations such as the Whitham, the gravity-capillary Whitham, and the Kawahara equations, confirming that the unstable spectrum of the corresponding linearized operators exhibits a figure 8 instability, as was observed before only numerically. Our method of proof uses a symplectic version of Kato's theory of similarity transformation to reduce the problem to determining the eigenvalues of a 3 \times 3 complex Hamiltonian and reversible matrix. Then, via a block-diagonalization procedure, we conjugate such matrix into a block-diagonal one composed of a 2 \times 2 Hamiltonian and reversible matrix, describing the unstable spectrum, and a single purely imaginary element describing the stable eigenvalue.
-
PubblicazioneElastic Plateau–Rayleigh instability in soft cylinders: Surface elasticity and periodic beading( 2025)The Plateau–Rayleigh instability shows that a cylindrical fluid flow can be destabilized by surface tension. Similarly, capillary forces can make an elastic cylinder unstable when the elastocapillary length is comparable to the cylinder's radius. While existing models predict a single isolated bulge as the result of an instability, experiments reveal a periodic sequence of bulges spaced out by thinned regions, a phenomenon known as beading instability. Most models assume that surface tension is independent of the deformation of the solid, neglecting variations due to surface stretch. In this work, we assume that surface tension arises from the deformation of material particles near the free surface, treating it as a pre-stretched elastic surface surrounding the body. Using the theoretical framework proposed by Gurtin and Murdoch, we show that a cylindrical solid can undergo a mechanical instability with a finite critical wavelength if the body is sufficiently soft or axially stretched. Post-buckling numerical simulations reveal a morphology in qualitative agreement with experimental observations. Period-halving secondary bifurcations are also observed. The results of this research have broad implications for soft materials, biomechanics, and microfabrication applications where surface tension plays a crucial role.
-
PubblicazioneUnique conformational dynamics and protein recognition of A-to-I hyper-edited dsRNA( 2025)Adenosine-to-inosine (A-to-I) editing is a highly abundant modification of double-stranded RNA (dsRNA) and plays an important role in posttranscriptional gene regulation. Editing of multiple inosines by the ADAR1 enzyme leads to A-to-I hyper-editing of non-coding dsRNA, such as 3'UTRs, transposable elements, or foreign pathogenic RNAs, and is implicated in immune response and human diseases including cancer. The structural consequences of hyper-editing and its role in protein binding are poorly understood. Here, we combine solution nuclear magnetic resonance spectroscopy (NMR), biophysical methods such as small-angle X-ray scattering, and molecular dynamics simulations to study the sequence-dependent effects on conformation and dynamics of A-to-I hyper-editing for a 20-mer dsRNA and recognition of such RNAs by Endonuclease V. By comparing non-edited, single-edited, and hyper-edited dsRNA, we identify unique conformational features and extensive dynamics associated with hyper-editing, resulting in significantly increased base-pair opening. Hyper-edited dsRNA is more extended and adopts a highly dynamic ensemble of canonical and non-canonical conformations, which lead to preferential binding by Endonuclease V. Our integrated experimental and computational analysis identifies unique structural and dynamic features that are likely linked to specific protein recognition and the unique biological consequences of hyper-editing.
-
PubblicazioneAn observation on the existence of stable generalized complex structures on ruled surfaces( 2025)We point out that any stable generalized complex structure on a sphere bundle over a closed surface of genus at least two must be of constant type.
-
PubblicazioneClifford-dressed variational principles for precise Loschmidt echoes( 2025)We extend the recently introduced Clifford-dressed time-dependent variational principle (TDVP) to efficiently compute many-body wave-function amplitudes in the computational basis. This advancement enhances the study of Loschmidt echoes, which generally require accurate calculations of the overlap between the evolved state and the initial wave function. By incorporating Clifford-disentangling gates during TDVP evolution, our method effectively controls entanglement growth while keeping the computation of these amplitudes accessible. Specifically, it reduces the problem to evaluating the overlap between a matrix product state (MPS) and a stabilizer state, a task that remains computationally feasible within the proposed framework. To demonstrate the effectiveness of this approach, we first benchmark it on the one-dimensional transverse-field Ising model. We then apply it to more challenging scenarios, including a nonintegrable next-to-nearest-neighbor Ising chain and a two-dimensional Ising model. Our results highlight the versatility and efficiency of the Clifford-augmented MPS, showcasing its capability to go beyond the evaluation of simple expectation values. This makes it a powerful tool for exploring various aspects of many-body quantum dynamics.