arXiv subjects

P. Shubham Parashar

Publications and source records attributed to P. Shubham Parashar.

3 recordsLinked to original sources

arXiv2026

Complete kinematic null for local kinetic dissipation in a sixfold-driven electron fluid

We identify a complete kinematic null in a two-dimensional electron fluid driven by a sixfold boundary pattern. In the $U_3^\pm$ channel of $D_{12}$, device symmetry excludes both the vector representation $R_1$ and the full first-gradient tensor $R_1\otimes R_1$. Hence at the symmetry-fixed center $\mathbf{j}(0)=0$ and $\partial_i j_j(0)=0$, so every local quadratic dissipative form built from the modeled charge/momentum field through first gradient order vanishes independently of the constitutive coefficients. In an $O(2)$-isotropic angular-harmonic kinetic model the first allowed local sector is $m=3$. For $νq^2/γ_3\ll1$, its heating is set by the previously derived coefficient $κ_4=v_F^4/(16γ_2^2γ_3)$. An explicit incompressible Stokes disk realizes a nonzero center signal, and a finite-moment kinetic boundary-value solution approaches the corresponding local benchmark. Within the local, fixed-current momentum-conserving Stokes regime, the normalized magnetic response can then be fitted for effective $γ_3$ and $γ_2$. Thus the sixfold drive creates a measurement point where ordinary local charge/momentum hydrodynamic dissipation is absent while a kinetic mode remains finite.

cond-mat.mes-hall↗

arXiv2026

Fourth-order closure obstruction and chiral nonlocality in circular kinetic magnetotransport

Closing an angular moment hierarchy at the stress level omits a definite back-action from higher Fermi-surface harmonics. For a circular two-dimensional Fermi surface, streaming changes angular momentum by one, so the shortest omitted sequence, $1\!\to\!2\!\to\!3\!\to\!2\!\to\!1$, adds a fourth-order term to the current eigenvalue, $Λ(q)=γ_1+νq^2-κ_4q^4+\cdots$, with $ν=v_F^2/(4γ_2)$ and $κ_4=ν^2/γ_3$. We call this missing operator term the fourth-order closure obstruction. Its gradient expansion is controlled when $νq^2/γ_3\ll1$. Circular symmetry carries the same coefficient into a radial bi-Laplacian within each conserved angular-momentum block, and retaining $m=3$ exactly, without a gradient expansion, amplifies higher radial modes monotonically. At zero field, positive collision rates exclude real-wave-number poles and response zeros; an equal-rate tail gives a square-root completion. A magnetic field makes the coefficient chiral, produces a Hall sign reversal, and enhances it when the $m=3$ harmonic is long lived. In the collisionless high-field limit, the complete hierarchy becomes a Bessel pole--zero ladder, while finite closures form rational approximants to it. The result separates a controlled low-gradient coefficient from its geometry- and field-dependent finite-wave-number completion.

cond-mat.mes-hall↗

arXiv2026

Thermal and viscous contrast in quantum Hall scanning-probe images

Quantum Hall scanning images are often read as maps of a local potential, temperature, or viscosity, whereas a probe records a finite-resolution functional of a transport operator. We formulate this functional using Landau-level projection, a particle-number Ward identity, magnetization-subtracted thermoelectric transport, a hydrodynamic Stokes-Ohm inversion, and finite-tip Fisher information. Two results follow in complementary transport regimes. In the strong-field, sharp-Landau-level regime, the defect-induced thermoelectric and electrical Hall contrasts of a smooth scalar defect obey $δα_{xy}^{tr}/δσ_{xy}=(E_c-μ)/(eT)$. At the retained long-wavelength order, the orbital form factor, defect geometry, and common tip kernel cancel after the heat-magnetization current is removed, so the zero of the thermoelectric contrast is pinned by energy weighting at $E_c=μ$ rather than by defect shape. In the hydrodynamic regime, the measurable $q^2$ tensor amplitudes mix Hall, longitudinal, transverse, boundary, electrothermal, and kinetic channels, so a Hall-odd image is not by itself a Hall-viscosity measurement. For a representative graphene geometry, a Schur-complement fit against the stated nuisance library yields a conditional one-standard-deviation sensitivity of approximately 68 square nanometers at SNR0 = 200, with boundary slip the limiting nuisance. The framework turns visual interpretation of quantum Hall nanoscopy into a quantitative observability test for electrical, thermoelectric, and viscous response channels.

cond-mat.mes-hall↗