Boundary versus bulk behavior of time-dependent correlation functions in one-dimensional quantum systems

We study the influence of reflective boundaries on time-dependent responses of one-dimensional quantum fluids at zero temperature beyond the low-energy approximation. Our analysis is based on an extension of effective mobile impurity models for nonlinear Luttinger liquids to the case of open boundary conditions. For integrable models, we show that boundary autocorrelations oscillate as a function of time with the same frequency as the corresponding bulk autocorrelations. This frequency can be identified as the band edge of elementary excitations. The amplitude of the oscillations decays as a power law with distinct exponents at the boundary and in the bulk, but boundary and bulk exponents are determined by the same coupling constant in the mobile impurity model. For nonintegrable models, we argue that the power-law decay of the oscillations is generic for autocorrelations in the bulk, but turns into an exponential decay at the boundary. Moreover, there is in general a nonuniversal shift of the boundary frequency in comparison with the band edge of bulk excitations. The predictions of our effective field theory are compared with numerical results obtained by time-dependent density matrix renormalization group (tDMRG) for both integrable and nonintegrable critical spin-$S$ chains with $S=1/2$, $1$ and $3/2$.Comment: 20 pages, 12 figure

Revealing single emitter spectral dynamics from intensity correlations in an ensemble fluorescence spectrum

We show that the single emitter linewidth underlying a broadened ensemble emission spectrum can be extracted from correlations among the stochastic intensity fluctuations in the ensemble spectrum. Spectral correlations can be observed at high temporal and spectral resolutions with a cross-correlated pair of avalanche photodiodes placed at the outputs of a scanning Michelson interferometer. As illustrated with simulations in conjunction with Fluorescence Correlation Spectroscopy, our approach overcomes ensemble and temporal inhomogeneous broadening to provide single emitter linewidths, even for emitters under weak, continuous, broadband excitation.Comment: 9 pages, 5 figure

Corruption in the Land Question and Protracted Conflict in Bungoma County, Kenya 1992-2019

Corruption is argued to be persistent and enduring matter of global concern. This article investigated corruption in the land question and protracted conflict in Bungoma County, Kenya 1992-2019. Corruption is defined in the form of bribery, land grabbing and privatization of public land. This study explored the dynamics of corruption and its influences on land distribution. It also examines how corruption is used in galvanizing intra-ethnic differentiation leading to protracted conflict on historical land injustice. Moreover, the study seeks to demonstrate how corruption has watered down peacebuilding initiatives in the aftermath of land-based conflict in Mount Elgon, Kenya. The study was anchored on a combination of greed versus grievance theoretical framework together with the theory of ethnic mobilization. The greed and grievance theory defines the problem of land grabbing as self-enrichment while ethnic mobilization theory explained the process by which political elites galvanize intra-ethnic differentiation leading to conflict between Soy and Mosop clans.  The study used a case study design to describe the characteristics and dynamics of corruption and its relation to land allocation and mobilization of members of the community into armed violence. The target population included residents of Mount Elgon constituency, politicians, members of the National Government Administrative Officers (NGAO), County government officials and the civil society.  Primary data was obtained from a non-partisan and gender sensitive samples of one hundred and thirty-seven respondents and twenty-four key informants.  The study found out that endemic corruption weaved with politics was a major hindrance to fair and transparent land allocation in the region. Moreover, women especially the widows and low income earners were the most disadvantaged in the process of land allocation. The study recommends an independent audit of the land dispensation to allow issuance to the deserving individuals. Key Words: Corruption, Protracted Land Conflict, Bungoma County, Chepyuk settlement scheme, Sabaot DOI: 10.7176/IAGS/91-05 Publication date:September 30th 202

Analysis of indentation size effect in copper and its alloys

For describing the indentation size effect (ISE), numerous models, which relate the load or hardness to the indent dimensions, have been proposed. Unfortunately, it is still difficult to associate the different parameters involved in such relationships with physical or mechanical properties of the material. This is an unsolved problem since the ISE can be associated with various causes such as workhardening, roughness, piling-up, sinking-in, indenter tip geometry, surface energy, varying composition and crystal anisotropy. For interpreting the change in hardness with indent size, an original approach is proposed on the basis of composite hardness modelling together with the use of a simple model, which allows the determination of the hardness–depth profile. Applied to copper and copper alloys, it is shown that it is possible to determine the maximum hardness value reached at the outer surface of the material and the distance over which both the ISE and the workhardening take place

Topological confinement in graphene bilayer quantum rings

We demonstrate the existence of localized electron and hole states in a ring-shaped potential kink in biased bilayer graphene. Within the continuum description, we show that for sharp potential steps the Dirac equation describing carrier states close to the K (or K') point of the first Brillouin zone can be solved analytically for a circular kink/anti-kink dot. The solutions exhibit interfacial states which exhibit Aharonov-Bohm oscillations as functions of the height of the potential step and/or the radius of the ring