Past exam of the mathematics course of the University of Cambridge 2026 ii Paper 3 21I d Solution Created 2026-09-24 Updated 2026-09-25
Approximate uniformly by finite sums ; their integral operators have finite-dimensional range and converge in operator norm, so is compact. If for , iterated integration over an ordered simplex gives . Thus , and compact spectral theory gives .
Past exam of the mathematics course of the University of Cambridge 2026 ii Paper 3 22H d Solution Created 2026-09-24 Updated 2026-09-25
Not for an arbitrary signed kernel. One can place very tall, very narrow spikes of at separated locations, with summable masses and total integral one, and matching still narrower spikes of an function accumulating at a Lebesgue point. Along a selected subsequence of dilations, a kernel spike lands on the matching function spike and contributes a fixed amount, while the total widths make the point a Lebesgue point. Thus compact support (or a suitable integrable radial majorant) cannot simply be dropped.
Past exam of the mathematics course of the University of Cambridge 2026 ii Paper 3 26L d Solution Created 2026-09-24 Updated 2026-09-25
On disjoint events with , set . Then almost surely and , but any common dominator has integral at least . Thus no integrable dominating variable exists.
Past exam of the mathematics course of the University of Cambridge 2026 ii Paper 3 30D a Solution Created 2026-09-24 Updated 2026-09-25
Past exam of the mathematics course of the University of Cambridge 2026 ii Paper 3 35E b Solution Created 2026-09-24 Updated 2026-09-25
Stirling and replacing the magnetization sum by an integral gives the stated form with , up to subexponential constants.
Past exam of the mathematics course of the University of Cambridge 2026 ii Paper 4 19F b ii Solution Created 2026-09-24 Updated 2026-09-25
The second Adams operation lies in the integral character ring, so with integers . Norm one forces exactly one coefficient to be ; evaluation at the identity makes the sign positive. Squaring is bijective on conjugacy classes as well, so distinct irreducibles remain distinct. Thus the permute the irreducible characters.
Past exam of the mathematics course of the University of Cambridge 2026 ii Paper 4 27K b Solution Created 2026-09-24 Updated 2026-09-25
A Poisson point process of intensity has independent counts on disjoint Borel sets, with whenever the integral is finite.
Past exam of the mathematics course of the University of Cambridge 2026 ii Paper 4 31D b ii Solution Created 2026-09-24 Updated 2026-09-25
Multiplying two asymptotic eigenfunctions by reduces the integral, after the phase coordinate , to a constant multiple of .
Past exam of the mathematics course of the University of Cambridge 2026 ii Paper 4 7D Solution Created 2026-09-24 Updated 2026-09-25
The identity theorem says analytic functions agreeing on a set with an interior accumulation point agree throughout a connected domain. Analytic continuation is an analytic function on a larger connected domain agreeing on a nonempty overlap. Factor the denominator as . For , contour closure below giveswith a removable value at ; this entire expression is the continuation. For , the displayed real-axis integral encloses only and equals , so it is not that continuation. Finally only at a boundary point of , so the zeros do not determine ; for example is nonzero and has them all.
Past exam of the mathematics course of the University of Cambridge 2026 ii Paper 4 9D a Solution Created 2026-09-24 Updated 2026-10-03
Probability density Created 2026-09-24 Updated 2026-10-03
Quadratic-mean to L1 density derivative 2026-10-07
Let , with . Since , the Cauchy-Schwarz inequality gives . Thus differentiability in quadratic mean suffices to differentiate bounded density integrals, even when the density itself has no useful pointwise derivative.
A bounded continuous factor and an integrable factor give a bounded velocity-integral gain on bounded continuous functions, with bound . The dominated convergence theorem proves joint continuity of the velocity integral. Combined with damped transport, the factorial bound for a Volterra iterate proves existence on arbitrary finite time slabs.
A perturbation can have negligible Hellinger distance but a large integral of its density's fourth power. At the uniform density on , let on and zero elsewhere, and let . Then and , so the score function is zero. However . Thus the density fourth-power functional is not continuous along this differentiable-in-quadratic-mean path, despite a bounded baseline and individually bounded nearby densities.
Square-integrable function Created 2026-10-05 Updated 2026-10-06
A measurable function is square-integrable when the integral of its squared absolute value is finite. Its equivalence class belongs to the L2 space; on a probability space, this means a finite second moment.
Stäckel potential Created 2026-10-06 Updated 2026-10-07
A Stäckel potential allows additive separation of the Hamilton-Jacobi equation in an orthogonal coordinate system. In axisymmetric prolate spheroidal coordinates, the relative-potential form is . It gives energy, axial angular momentum and an independent third separation integral. Here is a one-variable generating function, not the gravitational constant. Generic bounded orbits are regular invariant-torus motions; resonance and coordinate degeneracy require separate treatment.
Statistical functional 2026-10-07
A statistical functional assigns a target value to each probability measure in a statistical model. Examples include an expected value, a quantile, and an integral of a power of a probability density function. Its behavior along statistical paths determines whether first-order influence-function representers are available.
A regular phase-mixed distribution in an axisymmetric Stäckel potential is even separately in and , because these integrals depend on those components only through squares. Odd integration then gives all three mixed second moments zero, even if the dependence produces azimuthal streaming. Bare stationarity alone is insufficient in degenerate resonant potentials with additional integrals. For example the isotropic harmonic Hamiltonian has the extra conserved ; a positive Gaussian with is a steady tracer and has nonzero . Its harmonic gravitational potential is a Stäckel potential in these spheroidal coordinates. This tracer need not itself source that harmonic gravitational potential. The alignment claim thus needs the phase-mixed three-integral hypothesis, not merely the weak form of Jeans theorem.
For with integral one, the Cauchy-Schwarz inequality makes the mass functional bounded on the weighted Hilbert space. The vector has norm one, so the velocity-reset projection is the orthogonal projection onto its span. Consequently is bounded and self-adjoint. This Hilbert geometry differs from the norm-one positive reset projection on phase-space .