Constructive Gelfand duality for C*-algebras

We present a constructive proof of Gelfand duality for C*-algebras by reducing the problem to Gelfand duality for real C*-algebras.Comment: 6page

Wilis: Architectural Modeling of Wireless Systems

The performance of a wireless system depends on the wireless channel as well as the algorithms used in the transceiver pipelines. Because physical phenomena affect transceiver pipelines in difficult to predict ways, detailed simulation of the entire transceiver system is needed to evaluate even a single processing block. Further, some protocol validations require simulation of rare events (say, 1 bit error in 109 bits), which means the protocol must simulate for a long enough time for such events to materialize. This requirement coupled with the heavy computation typical of most physical-layer processing, rules out pure software solutions. In this paper we describe WiLIS, an FPGA-based hybrid hardware-software system designed to facilitate the development of wireless protocols. We then use WiLIS to evaluate several microarchitectures for measuring very low bit-error rates (BER). We demonstrate, for the first time, that the recently proposed SoftPHY can be implemented efficiently in hardware

A Test of the Adaptive Market Hypothesis using a Time-Varying AR Model in Japan

This study examines the adaptive market hypothesis (AMH) in Japanese stock markets (TOPIX and TSE2). In particular, we measure the degree of market efficiency by using a time-varying model approach. The empirical results show that (1) the degree of market efficiency changes over time in the two markets, (2) the level of market efficiency of the TSE2 is lower than that of the TOPIX in most periods, and (3) the market efficiency of the TOPIX has evolved, but that of the TSE2 has not. We conclude that the results support the AMH for the more qualified stock market in Japan.Comment: 10 pages, 2 figure, 2 table

The Dixmier property and tracial states for C*-algebras

A.T. was partially supported by an NSERC Postdoctoral Fellowship and through the EPSRC grant EP/N00874X/1. Acknowledgements We are grateful to Luis Santiago for helpful discussions at an early stage of this investigation. We would also like to thank the referee for providing helpful comments, which have led to a number of improvements.Peer reviewedPublisher PD

Classifying C∗C^*-algebras with both finite and infinite subquotients

We give a classification result for a certain class of $C^{*}$-algebras $\mathfrak{A}$ over a finite topological space $X$ in which there exists an open set $U$ of $X$ such that $U$ separates the finite and infinite subquotients of $\mathfrak{A}$. We will apply our results to $C^{*}$-algebras arising from graphs.Comment: Version III: No changes to the text. We only report that Lemma 4.5 is not correct as stated. See arXiv:1505.05951 for the corrected version of Lemma 4.5. As noted in arXiv:1505.05951, the main results of this paper are true verbatim. Version II: Improved some results in Section 3 and loosened the assumptions in Definition 4.

Comparison theory and smooth minimal C*-dynamics

We prove that the C*-algebra of a minimal diffeomorphism satisfies Blackadar's Fundamental Comparability Property for positive elements. This leads to the classification, in terms of K-theory and traces, of the isomorphism classes of countably generated Hilbert modules over such algebras, and to a similar classification for the closures of unitary orbits of self-adjoint elements. We also obtain a structure theorem for the Cuntz semigroup in this setting, and prove a conjecture of Blackadar and Handelman: the lower semicontinuous dimension functions are weakly dense in the space of all dimension functions. These results continue to hold in the broader setting of unital simple ASH algebras with slow dimension growth and stable rank one. Our main tool is a sharp bound on the radius of comparison of a recursive subhomogeneous C*-algebra. This is also used to construct uncountably many non-Morita-equivalent simple separable amenable C*-algebras with the same K-theory and tracial state space, providing a C*-algebraic analogue of McDuff's uncountable family of II_1 factors. We prove in passing that the range of the radius of comparison is exhausted by simple C*-algebras.Comment: 30 pages, no figure

Unit root testing under a local break in trend using partial information on the break date*

We consider unit root testing allowing for a break in trend when partial information is available regarding the location of the break date. This takes the form of knowledge of a relatively narrow window of data within which the break takes place, should it occur at all. For such circumstances, we suggest employing a union of rejections strategy, which combines a unit root test that allows for a trend break somewhere within the window, with a unit root test that makes no allowance for a trend break. Asymptotic and _nite sample evidence shows that our suggested strategy works well, provided that, when a break does occur, the partial information is correct. An empirical application to UK interest rate data containing the 1973 ‘oil shock’ is also considered

Relationship between aetiology and left ventricular systolic dysfunction in hypertrophic cardiomyopathy.

BACKGROUND: Severe left ventricular (LV) systolic dysfunction is an uncommon complication of hypertrophic cardiomyopathy (HCM) that is associated with poor prognosis. Small observational series suggest that patients with rare causes of HCM are more likely to develop systolic impairment than those with idiopathic disease or mutations in cardiac sarcomeric protein genes. The aim of this study was to test this hypothesis by comparing the prevalence of systolic dysfunction and its impact on prognosis in patients with different causes of HCM. METHODS AND RESULTS: 1697 patients (52 (40-63) years, 1160 (68%) males) with HCM followed at two European referral centres were studied. Diagnosis of specific aetiologies was made on the basis of clinical examination, cardiac imaging and targeted genetic and biochemical testing. The primary survival outcome was all-cause mortality or heart transplantation (HTx) for end-stage heart failure (HF). Secondary outcomes were HF-related death, sudden cardiac death, stroke-related death and non-cardiovascular death. Systolic dysfunction (LV ejection fraction <50% by two-dimensional (2D) echocardiography) at first evaluation was more frequent in rare phenocopies than in idiopathic or sarcomeric HCM (105/409 (26%) vs 40/1288 (3%), respectively (p<0.0001)). All-cause death/HTx and HF-related death were more frequent in rare phenocopies compared with idiopathic or sarcomeric HCM (p<0.0001). All-cause mortality and HF-related death were highest in patients with cardiac amyloidosis (p<0.0001). CONCLUSIONS: In adults with HCM, LV systolic dysfunction is more frequent in those with rare phenocopies. When combined with age at presentation, it is a marker for specific aetiologies and is associated with poorer long-term survival