52,091 research outputs found
Clearing Up Some Conceptual Confusions About Conspiracy Theory Theorising
A reply to Gérald Bronner, Véronique Campion-Vincent, Sylvain Delouvée, Sebastian Dieguez, Nicolas Gauvrit, Anthony Lantian, and Pascal Wagner-Egger's piece, '“They” Respond: Comments on Basham et al.’s “Social Science’s Conspiracy-Theory Panic: Now They Want to Cure Everyone”
Density-operator theory of orbital magnetic susceptibility in periodic insulators
The theoretical treatment of homogeneous static magnetic fields in periodic
systems is challenging, as the corresponding vector potential breaks the
translational invariance of the Hamiltonian. Based on density operators and
perturbation theory, we propose, for insulators, a periodic framework for the
treatment of magnetic fields up to arbitrary order of perturbation, similar to
widely used schemes for electric fields. The second-order term delivers a new,
remarkably simple, formulation of the macroscopic orbital magnetic
susceptibility for periodic insulators. We validate the latter expression using
a tight-binding model, analytically from the present theory and numerically
from the large-size limit of a finite cluster, with excellent numerical
agreement.Comment: 5 pages including 2 figures; accepted for publication in Phys. Rev.
Optimality of feedback control for qubit purification under inefficient measurement
A quantum system may be purified, i.e., projected into a pure state, faster if one applies feedback operations during the measurement process. However, the existing results suggest that such an enhancement is only possible when the measurement efficiency exceeds 0.5, which is difficult to achieve experimentally. We address the task of finding the global optimal feedback control for purifying a single qubit in the presence of measurement inefficiency. We use the Bloch vector length, a more physical and practical quantity than purity, to assess the quality of the state, and employ a backward-iteration algorithm to find the globally optimal strategy. Our results show that a speedup is available for quantum efficiencies well below 0.5, which opens the possibility of experimental implementation in existing systems
Wet impregnation of a commercial low cost silica using DETA for a fast post-combustion CO2 capture process
We acknowledge EPSRC for the Grants EP/J019720/1 and EP/J019704/1.Peer reviewe
Bank Liquidity, Interbank Markets, and Monetary Policy
A major lesson of the recent financial crisis is that the interbank lending market is crucial for banks facing large uncertainty regarding their liquidity needs. This paper studies the efficiency of the interbank lending market in allocating funds. We consider two different types of liquidity shocks leading to di¤erent implications for optimal policy by the central bank. We show that, when confronted with a distribu- tional liquidity-shock crisis that causes a large disparity in the liquidity held among banks, the central bank should lower the interbank rate. This view implies that the traditional tenet prescribing the separation between prudential regulation and mon- etary policy should be abandoned. In addition, we show that, during an aggregate liquidity crisis, central banks should manage the aggregate volume of liquidity. Two di¤erent instruments, interest rates and liquidity injection, are therefore required to cope with the two di¤erent types of liquidity shocks. Finally, we show that failure to cut interest rates during a crisis erodes financial stability by increasing the risk of bank runs.bank liquidity;interbank markets;central bank policy;financial fragility;bank runs
Stationary processes whose filtrations are standard
We study the standard property of the natural filtration associated to a 0--1
valued stationary process. In our main result we show that if the process has
summable memory decay, then the associated filtration is standard. We prove it
by coupling techniques. For a process whose associated filtration is standard,
we construct a product type filtration extending it, based upon the usual
couplings and the Vershik's criterion for standardness.Comment: Published at http://dx.doi.org/10.1214/009117906000000151 in the
Annals of Probability (http://www.imstat.org/aop/) by the Institute of
Mathematical Statistics (http://www.imstat.org
Optimal Resources for Topological 2D Stabilizer Codes: Comparative Study
We study the resources needed to construct topological 2D stabilizer codes as
a way to estimate in part their efficiency and this leads us to perform a
comparative study of surface codes and color codes. This study clarifies the
similarities and differences between these two types of stabilizer codes. We
compute the error correcting rate for surface codes and color
codes in several instances. On the torus, typical values are and
, but we find that the optimal values are and . For
planar codes, a typical value is , while we find that the optimal values
are and . In general, a color code encodes twice as much
logical qubits as a surface code does.Comment: revtex, 6 pages, 7 figure
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