Guided SH modes between rigid and free planes Created 2026-09-24 Updated 2026-10-14
For a layer with rigid lower boundary and traction-free upper boundary, an SH mode
has
and dispersion
Its cutoff is , its phase speed is , and its group speed is .
Continuous semimartingale decomposition Created 2026-09-24 Updated 2026-09-24
A continuous semimartingale has a decomposition in which both the local-martingale and finite-variation parts are continuous.
Levine-Tristram signature Created 2026-09-24 Updated 2026-10-14
For , the Levine-Tristram signature is the signature of the Hermitian matrix
It is locally constant away from unit roots of the Alexander polynomial of a knot.
At , this becomes the signature of a knot.
Curvature of the round unit sphere Created 2026-09-24 Updated 2026-10-14
With outward normal , the unit sphere has . The Gauss equation therefore gives sectional curvature one on every tangent two-plane.
Ricci curvature Created 2026-09-24 Updated 2026-10-25
Ricci curvature is the trace of the Riemann curvature tensor in its first and third arguments. For a unit tangent vector and an orthonormal basis ,
Brownian time reversal for fixed-strike lookback extrema Created 2026-09-24 Updated 2026-10-03
For a Brownian motion with drift , the process on has the same law as . Therefore
have the same distribution, which equates the corresponding geometric-Brownian lookback payoffs.
Power payoff in the Black-Scholes model Created 2026-09-24 Updated 2026-10-03
For the payoff , risk-neutral valuation gives
Its delta hedge holds units of the risky asset.
Compactness transfer of finite nonrigidity Created 2026-09-24 Updated 2026-09-24
If a theory has arbitrarily large finite nonrigid models, expand its language by a unary function , axiomatize that is an automorphism, require to move some element, and add sentences demanding at least elements for every . Every finite fragment has a sufficiently large finite nonrigid model, so compactness supplies an infinite nonrigid model.
Second variation of Riemannian arc length Created 2026-09-24 Updated 2026-10-05
For a unit-speed geodesic and a fixed-endpoint variation, the second variation of length is the index form of the normal component of its variation vector field.
Ribbon knot Created 2026-09-24 Updated 2026-09-24
Pressure gradient in a translating and squeezing finite gap Created 2026-09-24 Updated 2026-10-14
For lower speed , stationary upper tangential speed, upper normal speed , and equal endpoint pressures, define . Then
where
Yoneda lemma Created 2026-09-24 Updated 2026-09-28
The Yoneda lemma gives natural bijections
and their contravariant analogues.
Local compactness plus uniform tail control Created 2026-09-24 Updated 2026-09-24
Strong convergence on every bounded region combines with a tail estimate uniform in the sequence to give global strong convergence.
Weak lower semicontinuity of a bounded-domain Schrodinger energy Created 2026-09-24 Updated 2026-09-24
On bounded with , weak convergence in makes the Dirichlet term lower semicontinuous and, by Rellich compactness, makes the potential term continuous. Thus
is weakly lower semicontinuous.
Fourier proof of Rellich compactness Created 2026-09-24 Updated 2026-09-24
Weak convergence on a bounded domain gives pointwise convergence of Fourier transforms and dominated convergence on bounded frequency balls. A uniform derivative bound controls the complementary high-frequency tails.
High-frequency control by a Sobolev derivative Created 2026-09-24 Updated 2026-09-24
For , Plancherel gives
Zero extension of H01 Created 2026-09-24 Updated 2026-09-24
By the definition of as the closure of compactly supported smooth functions, extension by zero maps it continuously into without creating a boundary distribution.
Spectral profile Created 2026-09-24 Updated 2026-10-06
The spectral profile minimizes a Dirichlet-form Rayleigh quotient over nonnegative functions supported on sets of stationary mass at most .
The regular construction relies on a regular derivation having exactly one terminal rule, at its end. In a general variable-based grammar several variables may each use terminal productions, so replacing every such production can introduce several copies of the second start variable.
Point probability for the maximum of simple symmetric random walk Created 2026-09-24 Updated 2026-09-24
For and a positive integer ,
Exactly one term can be nonzero because has the parity of .

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