Charge fluctuation induced dephasing of exchange coupled spin qubits

Exchange coupled {\it spin} qubits in semiconductor nanostructures are shown to be vulnerable to dephasing caused by {\it charge noise} invariably present in the semiconductor environment. This decoherence of exchange gate by environmental charge fluctuations arises from the fundamental Coulombic nature of the Heisenberg coupling, and presents a serious challenge to the scalability of the widely studied exchange gate solid state spin quantum computer architectures. We estimate dephasing times for coupled spin qubits in a wide range (from 1 ns up to $> 1 \mu$s) depending on the exchange coupling strength and its sensitivity to charge fluctuations.Comment: 4 pages, 3 figure

Liquidity Shocks, Systemic Risk, and Market Collapse: Theory and Application to the Market for Perps

Traditional explanations of market crashes rely on the collapse of an asset price bubble or the exacerbation of an information asymmetry sufficient to cause less-informed participants to withdraw from the market. We show that markets can crash even though asset prices have not deviated from fundamental values and information is shared symmetrically among all market participants. We present a model in which markets crash when investors shift their beliefs about the liquidity of the secondary market. While such shifts in liquidity may be a factor in explaining many market crashes, the collapse of the market for perpetual floating-rate notes (perps) provides an especially clear illustration of the theory because a shift in liquidity beliefs appears to have been the sole determinant of the market crash. Such a shift can be precipitated by a systemic liquidity shock that is transitory or permanent. The latter proved to be the case with perps because perceptions of the liquidity of the secondary market were permanently altered. In addition to providing new insights into why markets crash, our findings are particularly relevant for unseasoned financial products that are often priced and marketed on the assumption that liquid secondary markets will develop. The perp episode also highlights the importance of broad placement of securities. Since market liquidity arises endogenously from the diversity of liquidity needs across the investor base, the broader the investor base, the lower the probability of a systemic liquidity shock. We also show how simple modifications in security design can mitigate the impact of such a shock should it occur.

The Alcohol Concern SMART recovery pilot project: final evaluation report

Evaluation of the Alcohol Concern/SMART Recovery (Self Mangement and Recovery Training) pilot project. The pilot project ran in England from 2008-2010 and was funded by the Department of Health

Big Jump of Record Warm Global Mean Surface Temperature in 2014–2016 Related to Unusually Large Oceanic Heat Releases

A 0.24°C jump of record warm global mean surface temperature (GMST) over the past three consecutive record‐breaking years (2014–2016) was highly unusual and largely a consequence of an El Niño that released unusually large amounts of ocean heat from the subsurface layer of the northwestern tropical Pacific. This heat had built up since the 1990s mainly due to greenhouse‐gas (GHG) forcing and possible remote oceanic effects. Model simulations and projections suggest that the fundamental cause, and robust predictor of large record‐breaking events of GMST in the 21st century, is GHG forcing rather than internal climate variability alone. Such events will increase in frequency, magnitude, and duration, as well as impact, in the future unless GHG forcing is reduced.Key PointsA 0.24°C jump of record warm global mean surface temperature over the past three consecutive years (2014–2016) was highly unusualIt was a result of an El Niño that released unusually large amounts of ocean heat previously accumulated in the western tropical PacificLarge record‐breaking events of global surface temperature are projected to increase in the future unless greenhouse‐gas forcing is reducedPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/142431/1/grl56888_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/142431/2/grl56888-sup-0001-2017GL076500-SI.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/142431/3/grl56888.pd

Non-collinear coupling between magnetic adatoms in carbon nanotubes

The long range character of the exchange coupling between localized magnetic moments indirectly mediated by the conduction electrons of metallic hosts often plays a significant role in determining the magnetic order of low-dimensional structures. In addition to this indirect coupling, here we show that the direct exchange interaction that arises when the moments are not too far apart may induce a non-collinear magnetic order that cannot be characterized by a Heisenberg-like interaction between the magnetic moments. We argue that this effect can be manipulated to control the magnetization alignment of magnetic dimers adsorbed to the walls of carbon nanotubes.Comment: 13 pages, 5 figures, submitted to PR

Implementation of the Licensing Act 2003: a national survey

The Licensing Act 2003 came into force in November 2005 and transferred responsibility for alcohol licensing to Local Authorities. This reports the findings of a nation wide survey of 225 (63%) local authority chairs of licensing committees/senior members of licensing teams in England evaluating the short-term impact of the Act

Self Consistent Expansion for the Molecular Beam Epitaxy Equation

Motivated by a controversy over the correct results derived from the dynamic renormalization group (DRG) analysis of the non linear molecular beam epitaxy (MBE) equation, a self-consistent expansion (SCE) for the non linear MBE theory is considered. The scaling exponents are obtained for spatially correlated noise of the general form $D({\vec r - \vec r',t - t'}) = 2D_0 | {\vec r - \vec r'} |^{2\rho - d} \delta ({t - t'})$. I find a lower critical dimension $d_c (\rho) = 4 + 2\rho$, above, which the linear MBE solution appears. Below the lower critical dimension a r-dependent strong-coupling solution is found. These results help to resolve the controversy over the correct exponents that describe non linear MBE, using a reliable method that proved itself in the past by predicting reasonable results for the Kardar-Parisi-Zhang (KPZ) system, where DRG failed to do so.Comment: 16 page

Out-of-plane nesting driven spin spiral in ultrathin Fe/Cu(001) films

Epitaxial ultrathin Fe films on fcc Cu(001) exhibit a spin spiral (SS), in contrast to the ferromagnetism of bulk bcc Fe. We study the in-plane and out-of-plane Fermi surfaces (FSs) of the SS in 8 monolayer Fe/Cu(001) films using energy dependent soft x-ray momentum-resolved photoemission spectroscopy. We show that the SS originates in nested regions confined to out-of-plane FSs, which are drastically modified compared to in-plane FSs. From precise reciprocal space maps in successive zones, we obtain the associated real space compressive strain of 1.5+-0.5% along c-axis. An autocorrelation analysis quantifies the incommensurate ordering vector q=(2pi/a)(0,0,~0.86), favoring a SS and consistent with magneto-optic Kerr effect experiments. The results reveal the importance of in-plane and out-of-plane FS mapping for ultrathin films.Comment: 4 pages, 3 figure

Age-specific mortality during the 1918 influenza pandemic: unravelling the mystery of high young adult mortality.

The worldwide spread of a novel influenza A (H1N1) virus in 2009 showed that influenza remains a significant health threat, even for individuals in the prime of life. This paper focuses on the unusually high young adult mortality observed during the Spanish flu pandemic of 1918. Using historical records from Canada and the U.S., we report a peak of mortality at the exact age of 28 during the pandemic and argue that this increased mortality resulted from an early life exposure to influenza during the previous Russian flu pandemic of 1889-90. We posit that in specific instances, development of immunological memory to an influenza virus strain in early life may lead to a dysregulated immune response to antigenically novel strains encountered in later life, thereby increasing the risk of death. Exposure during critical periods of development could also create holes in the T cell repertoire and impair fetal maturation in general, thereby increasing mortality from infectious diseases later in life. Knowledge of the age-pattern of susceptibility to mortality from influenza could improve crisis management during future influenza pandemics