33,300 research outputs found
Geometric phase and gauge theory structure in quantum computing
We discuss the presence of a geometrical phase in the evolution of a qubit
state and its gauge structure. The time evolution operator is found to be the
free energy operator, rather than the Hamiltonian operator.Comment: 5 pages, presented at Fifth International Workshop DICE2010:
Space-Time-Matter - current issues in quantum mechanics and beyond,
Castiglioncello (Tuscany), September 13-17, 201
Mapping prior information onto LMI eigenvalue-regions for discrete-time subspace identification
In subspace identification, prior information can be used to constrain the
eigenvalues of the estimated state-space model by defining corresponding LMI
regions. In this paper, first we argue on what kind of practical information
can be extracted from historical data or step-response experiments to possibly
improve the dynamical properties of the corresponding model and, also, on how
to mitigate the effect of the uncertainty on such information. For instance,
prior knowledge regarding the overshoot, the period between damped oscillations
and settling time may be useful to constraint the possible locations of the
eigenvalues of the discrete-time model. Then, we show how to map the prior
information onto LMI regions and, when the obtaining regions are non-convex, to
obtain convex approximations.Comment: Under revie
An ab-initio theoretical investigation of the soft-magnetic properties of permalloys
We study Ni80Fe20-based permalloys with the relativistic spin-polarized
Korringa-Kohn-Rostoker electronic structure method. Treating the compositional
disorder with the coherent potential approximation, we investigate how the
magnetocrystalline anisotropy, K, and magnetostriction, lambda, of Ni-rich
Ni-Fe alloys vary with the addition of small amounts of non-magnetic transition
metals, Cu and Mo. From our calculations we follow the trends in K and lambda
and find the compositions of Ni-Fe-Cu and Ni-Fe-Mo where both are near zero.
These high permeability compositions of Ni-Fe-Cu and Ni-Fe-Mo match well with
those discovered experimentally. We monitor the connection of the magnetic
anisotropy with the number of minority spin electrons, Nmin. By raising Nmin
via artificially increasing the band-filling of Ni80Fe20, we are able to
reproduce the key features that underpin the magnetic softening we find in the
ternary alloys. The effect of band-filling on the dependence of
magnetocrystalline anisotropy on atomic short-range order in Ni80Fe20 is also
studied. Our calculations, based on a static concentration wave theory,
indicate that the susceptibility of the high permeability of the Ni-Fe-Cu and
Ni-Fe-Mo alloys to their annealing conditions is also strongly dependent on the
alloys' compositions. An ideal soft magnet appears from these calculations.Comment: 20 pages, 6 figure
Noblesse Oblige? Determinants of Survival in a Life and Death Situation
This paper explored the determinants of survival in a life and death situation created by an external and unpredictable shock. We are interested to see whether pro-social behaviour matters in such extreme situations. We therefore focus on the sinking of the RMS Titanic as a quasi-natural experiment do provide behavioural evidence which is rare in such a controlled and life threatening event. The empirical results support that social norm such as �women and children first� survive in such an environment. We also observe that women of reproductive age have a higher probability of surviving among women. On the other hand, we observe that crew members used their information advantage and their better access to resources (e.g. lifeboats) to generate a higher probability of surviving. The paper also finds that passenger class, fitness, group size, and cultural background matter.Decision under Pressure, Altruism, Social Norms, Interdependent Preferences, Excess of Demand
Surviving the Titanic Disaster: Economic, Natural and Social Determinants
The sinking of the Titanic in April 1912 took the lives of 68 percent of the people aboard. Who survived? It was women and children who had a higher probability of being saved, not men. Likewise, people traveling in first class had a better chance of survival than those in second and third class. British passengers were more likely to perish than members of other nations.This extreme event represents a rare case of a well-documented life and death situation where social norms were enforced. This paper shows that economic analysis can account for human behavior in such situations.decision under pressure, tragic events and disasters, survival, quasi-natural experiment, altruism
Surviving the Titanic Disaster: Economic, Natural and Social Determinants
The sinking of the Titanic in April 1912 took the lives of 68 percent of the people aboard. Who survived? It was women and children who had a higher probability of being saved, not men. Likewise, people traveling in first class had a better chance of survival than those in second and third class. British passengers were more likely to perish than members of other nations. This extreme event represents a rare case of a well-documented life and death situation where social norms were enforced. This paper shows that economic analysis can account for human behavior in such situations.Decision under Pressure, Tragic Events and Disasters, Survival, Quasi-Natural Experiment, Altruism
On the Logarithmic Asymptotics of the Sixth Painleve' Equation (Summer 2007)
We study the solutions of the sixth Painlev\'e equation with a logarithmic
asymptotic behavior at a critical point. We compute the monodromy group
associated to the solutions by the method of monodromy preserving deformations
and we characterize the asymptotic behavior in terms of the monodromy itself.Comment: LaTeX with 8 figure
Noblesse Oblige? Determinants of Survival in a Life and Death Situation
This paper explored the determinants of survival in a life and death situation created by an external and unpredictable shock. We are interested to see whether pro-social behaviour matters in such extreme situations. We therefore focus on the sinking of the RMS Titanic as a quasi-natural experiment do provide behavioural evidence which is rare in such a controlled and life threatening event. The empirical results support that social norm such as “women and children first” survive in such an environment. We also observe that women of reproductive age have a higher probability of surviving among women. On the other hand, we observe that crew members used their information advantage and their better access to resources (e.g. lifeboats) to generate a higher probability of surviving. The paper also finds that passenger class, fitness, group size, and cultural background matter.decision under pressure, altruism, social norms, interdependent preferences, excess of demand
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