28,607 research outputs found
Theoretical and Numerical Analysis of an Optimal Execution Problem with Uncertain Market Impact
This paper is a continuation of Ishitani and Kato (2015), in which we derived
a continuous-time value function corresponding to an optimal execution problem
with uncertain market impact as the limit of a discrete-time value function.
Here, we investigate some properties of the derived value function. In
particular, we show that the function is continuous and has the semigroup
property, which is strongly related to the Hamilton-Jacobi-Bellman
quasi-variational inequality. Moreover, we show that noise in market impact
causes risk-neutral assessment to underestimate the impact cost. We also study
typical examples under a log-linear/quadratic market impact function with
Gamma-distributed noise.Comment: 24 pages, 14 figures. Continuation of the paper arXiv:1301.648
Closed formula for the relative entropy of entanglement in all dimensions
The relative entropy of entanglement is defined in terms of the relative
entropy between an entangled state and its closest separable state (CSS). Given
a multipartite-state on the boundary of the set of separable states, we find a
closed formula for all the entangled state for which this state is a CSS. Quite
amazing, our formula holds for multipartite states in all dimensions. In
addition we show that if an entangled state is full rank, then its CSS is
unique. For the bipartite case of two qubits our formula reduce to the one
given in Phys. Rev. A 78, 032310 (2008).Comment: 8 pages, 1 figure, significantly revised; theorem 1 is now providing
necessary and sufficient conditions to determine if a state is CS
Adiabatic Evolution for Systems with Infinitely many Eigenvalue Crossings
We formulate an adiabatic theorem adapted to models that present an
instantaneous eigenvalue experiencing an infinite number of crossings with the
rest of the spectrum. We give an upper bound on the leading correction terms
with respect to the adiabatic limit. The result requires only differentiability
of the considered spectral projector, and some geometric hypothesis on the
local behaviour of the eigenvalues at the crossings
Design and control of spin gates in two quantum dots arrays
We study the spin-spin interaction between quantum dots coupled through a two
dimensional electron gas with spin-orbit interaction. We show that the
interplay between transverse electron focusing and spin-orbit coupling allows
to dynamically change the symmetry of the effective spin-spin Hamiltonian. That
is, the interaction can be changed from Ising-like to Heisenberg-like and vice
versa. The sign and magnitude of the coupling constant can also be tuned.Comment: 4 pages, 3 figure
First Principles Study of the Electronic and Vibrational Properties of LiNbO2
In the layered transition metal oxide LiNbO the Nb () ion is
trigonal-prismatically coordinated with O ions, with the resulting crystal
field leading to a single band system for low energy properties. A
tight-binding representation shows that intraplanar second neighbor hopping
meV dominates the first neighbor interaction ( meV). The
first and third neighbor couplings are strongly modified by oxygen
displacements of the symmetric Raman-active vibrational mode, and
electron-phonon coupling to this motion may provide the coupling mechanism for
superconductivity in Li-deficient samples (where K). We calculate all
zone-center phonon modes, identify infrared (IR) and Raman active modes, and
report LO-TO splitting of the IR modes. The Born effective charges for the
metal ions are found to have considerable anisotropy reflecting the degree to
which the ions participate in interlayer coupling and covalent bonding. Insight
into the microscopic origin of the valence band density, composed of Nb
states with some mixing of O states, is obtained from examining
Wannier functions for these bands.Comment: 12 pages, 7 figures; Updated with reviewer comments; Updated
reference
Avaliação de cultivares de mandioca em Altamira - Pará.
bitstream/item/64570/1/Altamira-PA8.pd
Curious Variables Experiment (CURVE). CCD photometry of active dwarf nova DI UMa
We report an analysis of photometric behaviour of DI UMa, an extremely active
dwarf nova. The observational campaign (completed in 2007) covers five
superoutbursts and four normal outbursts. We examined principal parameters of
the system to understand peculiarities of DI UMa, and other active cataclysmic
variables. Based on precise photometric measurements, temporal light curve
behaviour, O-C analysis, and power spectrum analysis, we investigated physical
parameters of the system. We found that the period of the supercycle now equals
31.45 +/-0.3 days. Observations during superoutbursts infer that the period of
superhumps equals P_sh = 0.055318(11) days (79.66 +/- 0.02 min). During
quiescence, the light curve reveals a modulation of period P_orb = 0.054579(6)
days (78.59 +/- 0.01 min), which we interpret as the orbital period of the
binary system. The values obtained allowed us to determine a fractional period
excess of 1.35% +/- 0.02%, which is surprisingly small compared to the usual
value for dwarf novae (2%-5%). A detailed O-C analysis was performed for two
superoutbursts with the most comprehensive coverage. In both cases, we detected
an increase in the superhump period with a mean rate of dot_P/P_sh =
4.4(1.0)*10^{-5}. Based on these measurements, we confirm that DI UMa is
probably a period bouncer, an old system that reached its period minimum a long
time ago, has a secondary that became a degenerate brown dwarf, the entire
system evolving now toward longer periods. DI UMa is an extremely interesting
object because we know only one more active ER UMa star with similar
characteristics (IX Dra).Comment: Accepted for publication in Astronomy & Astrophysic
Mandioca: resultados preliminares de pesquisa na Transamazônica - PA.
bitstream/item/66788/1/Altamira-Doc3.pd
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