998 research outputs found
Interferometric signature of non-Abelian anyons
We consider the tunneling current through a double point-contact Fabry-PĂ©rot interferometer such as used in recent experimental studies of the fractional quantum Hall plateau at filling fraction v=5/2. We compare the predictions of several different models of the state of the electrons at this plateau: the Moore-Read, anti-Pfaffian, SU(2)_2 NAF, K=8 strong pairing, and (3,3,1) states. All of these predict the existence of charge e/4 quasiparticles, but the first three are non-Abelian while the last two are Abelian. We give explicit formulas for the scaling of charge e/2 and charge e/4 quasiparticle contributions to the current as a function of temperature, gate voltage, and distance between the two point contacts for all three models. Based on these, we analyze several possible explanations of two phenomena reported for recent experiments by Willett et al., namely, halving of the period of the observed resistance oscillations with rising temperature and alternation between the same two observed periods at low temperatures as the area of the interference loop is varied with a side gate. We conclude that the most likely explanation is that the observed alternation is due to switching between even and odd numbers of charge e/4 quasiparticles enclosed within the loop as a function of side-gate voltage, which is a clear signature of the presence of non-Abelian anyons. However, there are important features of the data which do not have a simple explanation within this picture. We suggest further experiments which could help rule out some possible scenarios. We make the corresponding predictions for future tunneling and interference experiments at the other observed second Landau level fractional quantum Hall states
Understanding Noncompetition Agreements: The 2014 Noncompete Survey Project
In recent years, scholars and policymakers have devoted considerable attention to the potential consequences of employment noncompetition agreements and to whether legislatures ought to reform the laws that govern the enforcement of these controversial contractual provisions. Unfortunately, much of this interestâand the content of proposed reformsâderives from anecdotal tales of burdensome noncompetes among low-wage workers and from scholarship that is either limited to slivers of the population (across all studies, less than 1%) or relies on strong assumptions about the incidence of noncompetition agreements. Better understanding of the use of noncompetes and effective noncompetition law reform requires a more complete picture of the frequency and distribution of noncompetes at the individual employee level. Accordingly, in 2014, we administered a nationwide survey of individuals in the labor force to ask them about their employment status, history, and future expectationsâincluding their experience with and understanding of noncompetition agreements. In this Article, we describe the methods we used to carry out this survey and refine the data for analysis in hopes of encouraging other researchers to use survey approaches to fill other, similarly important gaps in our knowledge. To illustrate the value of the survey project, we present a surprising empirical finding from our data, one that raises questions about existing scholarship and theories about why employers use noncompetes: We find little evidence that the incidence of noncompetition agreements in a state (after controlling for potentially confounding factors) has any relationship to the level of enforcement of such agreements in that state. In other words, an employee in California (where noncompetes are prohibited) appears to be just as likely to labor under a noncompete as an employee in Florida (where noncompetes are much more likely to be enforced)
The non-Abelian Interferometer
We consider the tunneling current through a double point-contact Fabry-Perot
interferometer such as used in recent experimental studies of the fractional
quantum Hall plateau at filling fraction nu=5/2. We compare the predictions of
several different models of the state of the electrons at this plateau: the
Moore-Read, anti-Pfaffian, SU(2)_2 NAF, K=8 strong pairing, and (3,3,1) states.
All of these predict the existence of charge e/4 quasiparticles, but the first
three are non-Abelian while the last two are Abelian. We give explicit formulas
for the scaling of charge e/2 and charge e/4 quasiparticle contributions to the
current as a function of temperature, gate voltage and distance between the two
point contacts for all three models. Based on these, we analyze several
possible explanations of two phenomena reported for recent experiments by
Willett et al., namely halving of the period of the observed resistance
oscillations with rising temperature and alternation between the same two
observed periods at low temperatures as the area of the interference loop is
varied with a side gate. We conclude that the most likely explanation is that
the observed alternation is due to switching between even and odd numbers of
charge e/4 quasiparticles enclosed within the loop as a function of side gate
voltage, which is a clear signature of the presence of non-Abelian anyons.
However, there are important features of the data which do not have a simple
explanation within this picture. We suggest further experiments which could
help rule out some possible scenarios. We make the corresponding predictions
for future tunneling and interference experiments at the other observed second
Landau level fractional quantum Hall states.Comment: 15 pages, 1 figure; v2: additional discussions and references added;
v3: clarifications and references updated; Appendix C has been removed and
incorporated in arXiv:0909.1056; this paper has been given the more clear,
accurate, and informative title "Interferometric signature of non-Abelian
anyons" in PRB by its editor
The role of FDG-PET/CT imaging in early detection of extra-cardiac complications of infective endocarditis
AbstractThe exact incidence of extra-cardiac complications (ECC) in patients with infective endocarditis (IE) is unknown but presumed to be high. These patients, although mostly asymptomatic, may require a more aggressive therapeutic approach. 18fluorodeoxyglucoseâpositron emission tomography/computed tomography (FDG-PET/CT) is used for the diagnosis of infections, but its role in the early diagnosis of IE complications is still unclear. This study aimed to evaluate the role of FDG-PET/CT in the early diagnosis of ECC in IE and its implications for medical management. We prospectively studied 40 consecutive patients with a confirmed diagnosis of IE (according to the modified Duke criteria) who underwent a whole body FDG-PET/CT study within 14 days from diagnosis. The FDG-PET/CT demonstrated ECC in 17 (42.5%) patients, while 8 (38.1%) of them were asymptomatic. The most frequent embolic sites were musculoskeletal and splenic. Owing to the FDG-PET/CT findings, treatment planning was modified in 14 (35%) patients. This included antibiotic treatment prolongation (27.5%), referral to surgical procedures (15%) and, most substantially, prevention of unnecessary device extraction (17.7%). According to our experiences, FDG-PET/CT imaging was useful in the detection of embolic and metastatic infections in IE. This clinical information had a significant diagnostic and therapeutic impact in managing IE disease
Non-competition covenants in acquisition deals
We study the changes in the consumersâ and producersâ surplus associated with acquisition deals where there is a non-competition covenant that forbids the seller from re-entering the market over a given time period. We find that these cquisition deals can lead to significant negative (positive) changes in the producersâ consumersâ) surplus, which decrease significantly with the time period of the covenant. We also show that the effect of the time period of the covenant on the welfare change can be positive or negative. It depends largely on the market conditions, such as the profit uncertainty and growth rate
Local Charge of the nu=5/2 Fractional Quantum Hall State
Electrons in two dimensions and strong magnetic fields effectively lose their
kinetic energy and display exotic behavior dominated by Coulomb forces. When
the ratio of electrons to magnetic flux quanta in the system is near 5/2, the
unique correlated phase that emerges is predicted to be gapped with
fractionally charged quasiparticles and a ground state degeneracy that grows
exponentially as these quasiparticles are introduced. Interestingly, the only
way to transform between the many ground states would be to braid the
fractional excitations around each other, a property with applications in
quantum information processing. Here we present the first observation of
localized quasiparticles at nu=5/2, confined to puddles by disorder. Using a
local electrometer to compare how quasiparticles at nu=5/2 and nu=7/3 charge
these puddles, we are able to extract the ratio of local charges for these
states. Averaged over several disorder configurations and samples, we find the
ratio to be 4/3, suggesting that the local charges are e/3 at seven thirds and
e/4 at five halves, in agreement with theoretical predictions. This
confirmation of localized e/4 quasiparticles is necessary for proposed
interferometry experiments to test statistics and computational ability of the
state at nu=5/2.Comment: 6 pages, 4 figures corrected titl
Shear bond strength and debonding characteristics of a new premixed self-etching with a reference total-etch adhesive
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