arXiv subjects

Truong-Son P. Van

Publications and source records attributed to Truong-Son P. Van.

5 recordsLinked to original sources

arXiv2026

The collapse time of weak measurement on $N$ entangled sites

We determine the time required for local weak measurements to collapse to one occupied site in an initial superposition of $N$ alternatives in the model of PRA 111, 032217 (2025). For equal initial occupation probabilities and a fixed confidence threshold $1-δ$, we prove $T_N/\ln N\to1/2$ in $L^1$, with time measured in units of the characteristic measurement time $τ_m$ of each detector. We also connect the asymptotic stabilization theorem of that work to a finite measurement: the first site to reach $1-δ$ is the eventual outcome with conditional probability exactly $1-δ$. The result corrects the previously proposed double-logarithmic asymptotic scaling. The finite-range numerical fit does not determine a constant asymptotic correction or a precise finite-$N$ law.

quant-ph↗

arXiv2026

A convexity-type invariant for the critical coagulation--fragmentation Hamilton--Jacobi equation

We study the critical coagulation--fragmentation equation with multiplicative coagulation kernel $a(s,\hat s)=s\hat s$ and constant fragmentation kernel $b(s,\hat s)=1$. Under the Bernstein transform, mass-conserving solutions correspond to solutions of a singular Hamilton--Jacobi equation studied by Tran and Van (Comm. Pure Appl. Math. 75 (2022), no. 6, 1292--1331). Through this correspondence they proved that mass-conserving solutions are unique on the full critical range $0<m\le1$, but could establish their existence only for $0<m<\tfrac12$. We identify a one-sided, convexity-type invariant that holds for Bernstein-transform data and is propagated by their viscous scheme as a genuine maximum-principle bound. We call it the half-slope invariant. It sharpens the curvature barrier and thereby extends mass-conserving existence to the entire critical range $0<m\le1$. Hence $m=1$ is the critical mass, confirming the threshold predicted by Vigil and Ziff (J. Colloid Interface Sci. 133 (1989), no. 1, 257--264). The same invariant appears in the radial partial-mass formulation of the two-dimensional Keller--Segel equation, whose critical mass is $8π$.

math.AP↗

arXiv2026

Error analysis of an acceleration corrected diffusion approximation of Langevin dynamics with background flow

We consider the problem of approximating the Langevin dynamics of inertial particles being transported by a background flow. In particular, we study an acceleration corrected advection-diffusion approximation to the Langevin dynamics, a popular approximation in the study of turbulent transport. We prove error estimates in the averaging regime in which the dimensionless relaxation timescale $\varepsilon$ is the small parameter. We show that for any finite time interval, the approximation error is of order $\mathcal{O}(\varepsilon)$ in the strong sense and $\mathcal{O}(\varepsilon^2)$ in the weak sense, whose optimality is checked against computational experiment. Furthermore, we present numerical evidence suggesting that this approximation also captures the long-time behavior of the Langevin dynamics.

math.PR↗

arXiv2025

Quantum Telegraph Behavior Without Photons

We show that a simple model of non-Hermitian noise gives rise to the telegraph switching behavior seen in experiments with single qubits, without any reference to the existence of photons as corpuscles. This lends support to a continuous collapse interpretation of quantum mechanics, but can also be viewed as a model of continuous detection of a steady-state process in the incoherent limit. We show explicitly that such a system obeys the Born rule for particle counting statistics, even though no particle behavior has been invoked at any point in the calculation.

quant-ph↗

arXiv2025

Measurement time of weak measurements on large entangled systems

It is well established that starting only with strong, projective quantum measurements, experiments can be designed to allow weak measurements, which lead to random walk between the possible final measurement outcomes. However, one can ask the reverse question: starting with only weak measurements, can all the results of standard strong measurements be recovered? Prior work has shown that some results can be, such as the Born rule for the probability of measurement outcomes as a function of wave intensity. In this paper we show that another crucial result can be reproduced by purely weak measurements, namely the collapse of a many-body, nonlocally entangled wave function on a time scale comparable to the characteristic time of a single, local measurement; for an entangled state of a single excitation among $N$ qubits, we find the collapse time scales as a double logarithm of $N$. This result affirms the self-consistency of the hypothesis that spontaneous weak measurements lie at the base of all physical measurements, independent of human observers.

quant-ph↗