6,392 research outputs found
An analogue of Ryser's Theorem for partial Sudoku squares
In 1956 Ryser gave a necessary and sufficient condition for a partial latin
rectangle to be completable to a latin square. In 1990 Hilton and Johnson
showed that Ryser's condition could be reformulated in terms of Hall's
Condition for partial latin squares. Thus Ryser's Theorem can be interpreted as
saying that any partial latin rectangle can be completed if and only if
satisfies Hall's Condition for partial latin squares.
We define Hall's Condition for partial Sudoku squares and show that Hall's
Condition for partial Sudoku squares gives a criterion for the completion of
partial Sudoku rectangles that is both necessary and sufficient. In the
particular case where , , , the result is especially simple, as
we show that any partial -Sudoku rectangle can be completed
(no further condition being necessary).Comment: 19 pages, 10 figure
Recovering refined surface normals for relighting clothing in dynamic scenes
In this paper we present a method to relight captured 3D video sequences of non-rigid, dynamic scenes, such as clothing of real actors, reconstructed from multiple view video. A view-dependent approach is introduced to refine an initial coarse surface reconstruction using shape-from-shading to estimate detailed surface normals. The prior surface approximation is used to constrain the simultaneous estimation of surface normals and scene illumination, under the assumption of Lambertian surface reflectance. This approach enables detailed surface normals of a moving non-rigid object to be estimated from a single image frame. Refined normal estimates from multiple views are integrated into a single surface normal map. This approach allows highly non-rigid surfaces, such as creases in clothing, to be relit whilst preserving the detailed dynamics observed in video
The nuclear scissors mode within two approaches (Wigner function moments versus RPA)
Two complementary methods to describe the collective motion, RPA and Wigner
function moments method, are compared on an example of a simple model -
harmonic oscillator with quadrupole-quadrupole residual interaction. It is
shown that they give identical formulae for eigenfrequencies and transition
probabilities of all collective excitations of the model including the scissors
mode, which here is the subject of our special attention. The exact relation
between the variables of the two methods and the respective dynamical equations
is established. The normalization factor of the "synthetic" scissors state and
its overlap with physical states are calculated analytically. The orthogonality
of the spurious state to all physical states is proved rigorously.Comment: 39 page
Generalised Moore spectra in a triangulated category
In this paper we consider a construction in an arbitrary triangulated
category T which resembles the notion of a Moore spectrum in algebraic
topology. Namely, given a compact object C of T satisfying some finite tilting
assumptions, we obtain a functor which "approximates" objects of the module
category of the endomorphism algebra of C in T. This generalises and extends a
construction of Jorgensen in connection with lifts of certain homological
functors of derived categories. We show that this new functor is well-behaved
with respect to short exact sequences and distinguished triangles, and as a
consequence we obtain a new way of embedding the module category in a
triangulated category. As an example of the theory, we recover Keller's
canonical embedding of the module category of a path algebra of a quiver with
no oriented cycles into its u-cluster category for u>1.Comment: 26 pages, improvement to exposition of the proof of Theorem 3.
Softening of the insulating phase near Tc for the photo-induced insulator-to-metal phase transition in vanadium dioxide
We use optical-pump terahertz-probe spectroscopy to investigate the
near-threshold behavior of the photoinduced insulator-to-metal (IM) transition
in vanadium dioxide thin films. Upon approaching Tc a reduction in the fluence
required to drive the IM transition is observed, consistent with a softening of
the insulating state due to an increasing metallic volume fraction (below the
percolation limit). This phase coexistence facilitates the growth of a
homogeneous metallic conducting phase following superheating via
photoexcitation. A simple dynamic model using Bruggeman effective medium theory
describes the observed initial condition sensitivity.Comment: accepted for publication in Physical Review Letter
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