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arXiv:2608.22547

Fractality of the Schrödinger Density for Rough Data

Masoud Ataei

math-phmath.APmath.PRquant-phSubmitted Aug 23, 2026• Announced Aug 25, 2026• 0 citations
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Abstract

The observable of the Talbot effect is the intensity behind the grating: the density of the evolving field, not the field itself. Its fractality was previously known only for step data with rational jumps. We prove the general case. For arbitrary real data of bounded variation with at least one jump, the density of the free Schrödinger evolution on the torus is fractal at almost every time, with graph of upper box dimension exactly three halves. Its critical Sobolev mass diverges logarithmically, at a rate given in closed form by Wiener's jump statistic of the datum and independent of the positions and phases of the jumps. The same rate is halved along time traces and doubled for the Airy flow, so the critical mass probes the dispersion relation. Transported by the rank calculus of derangetropy operators, the theory equips every probability law with a quantum carpet: Gauss-sum revivals on quantile cells at rational times, a universal fractal at almost every other. The spectral growth rate of a single measured intensity profile returns the jump content of the grating, a prediction open to test in optical and matter-wave interferometry.

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The observable of the Talbot effect is the intensity behind the grating: the density of the evolving field, not the field itself. Its fractality was previously known only for step data with rational jumps. We prove the general case. For arbitrary real data of bounded variation with at least one jump, the density of the free Schrödinger evolution on the torus is fractal at almost every time, with graph of upper box dimension exactly three halves. Its critical Sobolev mass diverges logarithmically, at a rate given in closed form by Wiener's jump statistic of the datum and independent of the positions and phases of the jumps. The same rate is halved along time traces and doubled for the Airy flow, so the critical mass probes the dispersion relation. Transported by the rank calculus of derangetropy operators, the theory equips every probability law with a quantum carpet: Gauss-sum revivals on quantile cells at rational times, a universal fractal at almost every other. The spectral growth rate of a single measured intensity profile returns the jump content of the grating, a prediction open to test in optical and matter-wave interferometry.
A quantum wave with probability density , confined by Dirichlet boundary conditions in a D-dimensional box of arbitrary shape and finite surface area, evolves from the uniform state . For almost all positions , the graph of the evolution of P is a fractal curve with dimension . For almost all times t, the graph of the spatial probability density P is a fractal hypersurface with dimension . When D = 1, there are, in addition to these generic time and space fractals, infinitely many special `quantum revival' times when P is piecewise constant, and infinitely many special spacetime slices for which the dimension of P is 5/4. If the surface of the box is a fractal with dimension , simple arguments suggest that the dimension of the time fractal is , and that of the space fractal is .
We propose a general construction of wave functions of arbitrary prescribed fractal dimension, for a wide class of quantum problems, including the infinite potential well, harmonic oscillator, linear potential, and free particle. The box-counting dimension of the probability density ${P}_{t}(x)\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}|\ensuremath{\Psi}(x,t){|}^{2}$ is shown not to change during the time evolution. We prove a universal relation Dt=1+Dx/2{D}_{t}{\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1+D}_{x}/2Dt​=1+Dx​/2 linking the dimensions of space cross sections Dx{D}_{x}Dx​ and time cross sections Dt{D}_{t}Dt​ of the fractal quantum carpets.
Any quantum (Schrödinger) wavefunction on a sphere is necessarily periodic in time. The corresponding statement down one dimension, for a circular line instead, is the quantum version of the 'Talbot effect' for a diffraction grating in paraxial optics (which is fully analogous to quantum mechanics). In the circle case the 'revival' of any initial wavefunction at the period, or 'Talbot time', is accompanied by a kind of partial revival at any rational fraction of the period, increasing in complexity for less simple fractions. In particular, any piecewise constant initial wavefunction is again piecewise constant at such times. By contrast, in the sphere case, the simplest piecewise constant wave, constant on hemispheres is shown not to retain its piecewise constancy at rational fractions of the period, but instead, rather strikingly, to develop infinities at calculable locations. The calculation requires the uniform asymptotic form of the Legendre polynomials together with the Poisson sum formula leading to Gauss sums.
Abstract Paper 5 of the Canonical Semantic Framework (CSF) established the minimal coherent grammar: a retained spectral band, a -graded microscopic fiber, an admissible operator class, five residual channels of admissibility failure, and an elementary lift realizing the minimal coherent defect profile. Those results were microscopic. They fixed the operator grammar of the theory but did not yet specify what a macroscopic observer, one who cannot resolve the internal quarter-turn cocycle of the fiber, actually measures. The present paper provides that step. It develops the macroscopic reduction of the grammar and shows that several central structures of observed physics arise as controlled shadows of the microscopic coherent transport. The reduction map. The canonical phase-averaging operator is the Hilbert–Schmidt orthogonal projection and completely positive, trace-preserving conditional expectation onto the grade-invariant observable algebra. It is not one choice among many decoherence prescriptions. It is the unique symmetry-compatible projection encoding macroscopic blindness to the grading, and it is forced by the microscopic grammar. The density operator. Paired with the positive observable state , the reduction produces which is a density operator. The density-matrix formalism of quantum mechanics is not assumed; it is recovered as the reduced description of a more structured object. The effective mass functional. The retained-band projector of Paper 5 is read as a bandlimit with cutoff on an action channel. The effective mass is then the out-of-band Hilbert–Schmidt load Mass is not primitive. It is the structural cost of maintaining coherent transport outside the retained admissible band. Kinematics. Under spectral dilation the exact formula for yields monotone growth of the out-of-band load with . Exact relativistic -scaling follows from a constitutive edge-density ansatz, stated as a modeled special case rather than as a universal theorem. Inertial stabilization. The Negative Jacobian Variational (NJV) compensator of Paper 5 is given its reduced dynamical role. Under an out-of-band dissipativity hypothesis, NJV contributes a linear damping term to the evolution of . The reduced observer experiences this damping as inertia; the stability bound is the precise mathematical content. Non-propagating correlation structure. A sector of microscopic structure supported at and commuting with the grading generator is fixed by and not generated by transport on the action base. This provides the geometric locus for entanglement-type correlations in the reduced theory. The propagation-speed parameter associated with such correlations is absent rather than superluminal; the construction is compatible with no-signaling by design. Two-fold loss. The Hilbert–Schmidt content invisible to the macroscopic observer decomposes orthogonally into two independent pieces: spectral loss (the out-of-band content measured by ) and algebraic loss (the inter-grade content, which we name residual coherence ). These are independent; one may vanish while the other does not. The reduced observer is blind to their sum. Worked example. Appendix D evaluates the reduction operator, the mass functional, and the residual coherence on the elementary lift of Paper 5 and on the leakage-only and pure-geometry counterexample pairs. The quantitative profile of each defect channel through the reduction is exhibited in closed form and matches the Paper 5 Appendix A numerics. What this paper does not claim. No full solution of the measurement problem. No universal relativistic scaling law. No derivation of the Standard Model spectrum, the up-quark anomaly and its expected vortex-core resolution are deferred to Paper 7, which develops the -scaling mass law. No Einstein field equations, the gravitational slot is stated as a structural statement, not derived. No engineering proposals. What this paper does claim. A precise reduction framework, canonical, positivity-preserving, symmetry-forced, that carries the microscopic CSF grammar into macroscopic effective phenomenology. From that reduction there emerge: density operators, a Born-compatible probability calculus, positive effective mass as out-of-band load, inertial stabilization as NJV dissipativity, and non-propagating correlation structure as invariant-sector persistence. The universe the macroscopic observer measures, on this reading, is what a coherent finite-acuity grammar looks like once its internal grading is projected out and its action channel is bandlimited. That is not a small claim. It is narrower than a theory of everything. It is also more defensible.
We demonstrate fractal noise in the quantum evolution of wave packets moving either ballistically or diffusively in periodic and quasiperiodic tight-binding lattices, respectively. For the ballistic case with various initial superpositions we obtain a space-time self-affine fractal $\ensuremath{\Psi}(x,t)$ which verifies the predictions by Berry for ``a particle in a box,'' in addition to quantum revivals. For the diffusive case self-similar fractal evolution is also obtained. These universal fractal features of quantum theory might be useful in the field of quantum information, for creating efficient quantum algorithms, and can possibly be detectable in scattering from nanostructures.