Induction from the diagonal subgroup of upper-triangular SL2 Created 2026-09-24 Updated 2026-09-24
If is the upper-triangular subgroup of and is one-dimensional on , then
is the direct sum of three pairwise nonisomorphic irreducibles. Their restrictions to have character supports given by the trivial character, the square orbit, and the nonsquare orbit, so their dimensions are .
Acoustic membrane dispersion asymptotics Created 2026-09-24 Updated 2026-09-24
For , the physical speed approaches as tends to zero and scales as as tends to infinity.
Splitting of three in Q of square root minus p Created 2026-09-24 Updated 2026-09-24
If and , then . The generator's minimal polynomial reduces modulo to , so splits into two distinct prime ideals of norm three.
Ramification of a prime Created 2026-09-24 Updated 2026-10-14
Ramification specializes to primes as follows: a prime ramifies in a number field when its prime-ideal factorization contains a factor with exponent greater than one.
Larmor precession of a spin coherent state Created 2026-09-24 Updated 2026-10-18
Under , a coherent spin direction precesses around the -axis with angular velocity .
Equatorial spin-three-halves coherent state Created 2026-09-24 Updated 2026-09-24
At azimuth , the normalized spin- coherent-state components are proportional to .
Press-Schechter formalism Created 2026-09-24 Updated 2026-09-24
The Press-Schechter formalism estimates the halo abundance from the Gaussian probability that a smoothed linear overdensity crosses the spherical-collapse threshold, with a factor of two enforcing total mass conservation.
Halo peak height Created 2026-09-24 Updated 2026-10-03
The peak height of a halo of mass is , where is the variance of the linear density field smoothed on the corresponding mass scale.
Elastohydrodynamic boundary layer of a filament Created 2026-09-24 Updated 2026-10-05
When viscous drag creates a large axial tension , a clamped filament turns toward its outer direction in a boundary layer of length .
Full spectrum Created 2026-09-24 Updated 2026-09-24
The full spectrum of an element is its spectrum together with every bounded component of its complement. Its complement is the unbounded resolvent component, and the maximum modulus principle controls a holomorphic function on each filled hole by its values on the spectral boundary.
Holomorphic functional calculus Created 2026-09-24 Updated 2026-09-24
For in a unital Banach algebra and holomorphic near , the holomorphic functional calculus defines
where winds once around the spectrum. It is a continuous unital algebra homomorphism and satisfies the spectral mapping theorem .
Spectrum in a closed unital subalgebra Created 2026-09-24 Updated 2026-09-24
If a closed unital subalgebra contains , then is obtained from by adjoining some bounded connected components of its complement. Membership of in is constant on every connected component of the resolvent set, and it always holds on the unbounded component.
Resolvent of an element Created 2026-09-24 Updated 2026-10-14
The resolvent is on the complement of the spectrum of an element. In a Banach algebra it is analytic there.
Finite-rank truncation of a compact Hermitian operator Created 2026-09-24 Updated 2026-09-28
If
then truncating the sum after terms gives finite-rank Hermitian with
Spectral representation of a thermal correlation function Created 2026-09-24 Updated 2026-09-28
A Matsubara correlator is obtained from the retarded spectral density by a Cauchy transform evaluated at an imaginary frequency.
Leading nonlinear eigenvalue shift in a Sturm-Liouville problem Created 2026-09-24 Updated 2026-09-29
For near a normalized simple null mode , put and . Orthogonality to yields
Failure of an Lp hyperplane trace Created 2026-09-24 Updated 2026-09-24
For , no bounded map from to can agree with restriction on continuous functions. Indeed,
has a fixed nonzero trace while .
W1p trace theorem on a half-space Created 2026-09-24 Updated 2026-10-05
For , boundary restriction on smooth functions extends uniquely to a bounded linear map . The estimate follows by applying the fundamental theorem of calculus on normal line segments and then integrating over the boundary variables.
Hölder space Created 2026-09-24 Updated 2026-10-14
A Hölder space consists of functions satisfying a Hölder condition. A bounded function belongs to when
Noncompactness of a Sobolev embedding by translation Created 2026-09-24 Updated 2026-10-14
Translations of one compactly supported bump have equal Sobolev norms. Widely separated translates have disjoint supports and remain a fixed positive distance apart in , obstructing compactness on an unbounded domain.

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