Endomorphism algebras arising from mutations

Let $A$ be a finite dimensional algebra over an algebraically closed field $k$, $\mathcal {D}^b(A)$ be the bounded derived category of $A$-mod and $A^{(m)}$ be the $m$-replicated algebra of $A$. In this paper, we investigate the structure properties of endomorphism algebras arising from silting mutation in $\mathcal {D}^b(A)$ and tilting mutation in $A^{(m)}$-mod.Comment: 16 pages. arXiv admin note: text overlap with arXiv:1005.0276 by other author

The educational cooperation between University of Nordland and Changchun University of Science and Technology

Masteroppgave i bedriftsøkonomi - Universitetet i Nordland, 201

Accounting comparability, audit effort and audit outcomes

The paper investigates the usefulness of accounting comparability for audit engagement. Comparability among peer firms in the same industry reflects the similarity and the relatedness of firms’ operating environment and accounting reporting. From two perspectives of “inherent business risk” and “external information efficiency”, comparability is helpful for auditors to assess client business risk and lowers the cost of information acquisition, processing, and testing. For a given firm, I hypothesize that the availability of information about comparable firms is helpful for auditors by improving audit accuracy and audit efficiency. The comparability proxy is based on a variety of measures including pair-wise earnings-return similarity (De Franco, Kothari and Verdi 2011), historical covariance of stock returns and cash flows, and earnings comparability controlling accounting choice differences. The empirical results show that accounting comparability is positively associated with audit quality and audit reporting accuracy as of a clean or a going-concern opinion. Meanwhile, comparability is negatively related to audit delay, audit fees, and the likelihood of auditor’s issuing a going-concern opinion. In totality, the study shows that industry-wise comparability enhances the utility of accounting information for external audit

Power Scaling of Uplink Massive MIMO Systems with Arbitrary-Rank Channel Means

This paper investigates the uplink achievable rates of massive multiple-input multiple-output (MIMO) antenna systems in Ricean fading channels, using maximal-ratio combining (MRC) and zero-forcing (ZF) receivers, assuming perfect and imperfect channel state information (CSI). In contrast to previous relevant works, the fast fading MIMO channel matrix is assumed to have an arbitrary-rank deterministic component as well as a Rayleigh-distributed random component. We derive tractable expressions for the achievable uplink rate in the large-antenna limit, along with approximating results that hold for any finite number of antennas. Based on these analytical results, we obtain the scaling law that the users' transmit power should satisfy, while maintaining a desirable quality of service. In particular, it is found that regardless of the Ricean $K$-factor, in the case of perfect CSI, the approximations converge to the same constant value as the exact results, as the number of base station antennas, $M$, grows large, while the transmit power of each user can be scaled down proportionally to $1/M$. If CSI is estimated with uncertainty, the same result holds true but only when the Ricean $K$-factor is non-zero. Otherwise, if the channel experiences Rayleigh fading, we can only cut the transmit power of each user proportionally to $1/\sqrt M$. In addition, we show that with an increasing Ricean $K$-factor, the uplink rates will converge to fixed values for both MRC and ZF receivers