Quantum anti-quenching of radiation from laser-driven structured plasma channels

We demonstrate that in the interaction of a high-power laser pulse with a structured solid-density plasma-channel, clear quantum signatures of stochastic radiation emission manifest, disclosing a novel avenue to studying the quantized nature of photon emission. In contrast to earlier findings we observe that the total radiated energy for very short interaction times, achieved by studying thin plasma channel targets, is significantly larger in a quantum radiation model as compared to a calculation including classical radiation reaction, i.e., we observe quantum anti-quenching. By means of a detailed analytical analysis and a refined test particle model, corroborated by a full kinetic plasma simulation, we demonstrate that this counter-intuitive behavior is due to the constant supply of energy to the setup through the driving laser. We comment on an experimental realization of the proposed setup, feasible at upcoming high-intensity laser facilities, since the required thin targets can be manufactured and the driving laser pulses provided with existing technology.Comment: 6 pages, 3 figure

Strong energy enhancement in a laser-driven plasma-based accelerator through stochastic friction

Conventionally, friction is understood as an efficient dissipation mechanism depleting a physical system of energy as an unavoidable feature of any realistic device involving moving parts, e.g., in mechanical brakes. In this work, we demonstrate that this intuitive picture loses validity in nonlinear quantum electrodynamics, exemplified in a scenario where spatially random friction counter-intuitively results in a highly directional energy flow. This peculiar behavior is caused by radiation friction, i.e., the energy loss of an accelerated charge due to the emission of radiation. We demonstrate analytically and numerically how radiation friction can enhance the performance of a specific class of laser-driven particle accelerators. We find the unexpected directional energy boost to be due to the particles' energy being reduced through friction whence the driving laser can accelerate them more efficiently. In a quantitative case we find the energy of the laser-accelerated particles to be enhanced by orders of magnitude.Comment: 14 pages, 3 figure

Social sustainability and residents' experiences in a new Chinese eco-city

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record.The article argues for a “humanizing” research agenda on newly-built forms of eco-urbanism, such as eco-cities. Taking the example of the Sino-Singapore Tianjin Eco-City, China, the article focuses on urban social sustainability with a specific focus on the lived experiences of new residents of the newly-built eco-city. Drawing on Jane Jacobs' work on the spaces of the city, the article's focus on residents' experiences underlines the key importance of social sustainability when analysing new flagship urban projects, and highlights the need to consider the relational networks of lived experiences of the city as well as the visions and techno-social designs of planners, policymakers and corporate actors in the development of eco-city projects

Challenging the eco-city: residents’ perceptions of social sustainability in Tianjin Eco-City, China

In this chapter, we make the case for ‘humanizing’ new-build urban mega-projects such as eco-cities by focusing on urban social sustainability, and on the experiences of new residents in newly-built cities such as Tianjin eco-city. We base our conceptual framework in the context of debates over social sustainability (Dempsey et al. 2011; Vallance et al. 2011; Woodcraft 2015), and argue that there is a need to also focus on the way(s) in which socially sustainable urban environments are constructed, in new urban spaces, through relational networks comprised by interactions between residents, buildings, facilities and specifc (e.g. domestic) spaces. In focusing on the spaces of urban social sustainability we draw on Jane Jacobs’ seminal work on, and critique of, the modern city (Jacobs 1961). Jacobs’ work is useful here because of its focus on moving past the plans, blueprints and rational urban visions proposed by master planners, engineers and architects, and towards valuing the role of the rather messier relationality found in the everyday city. [...

The Sorting Index and Permutation Codes

In the combinatorial study of the coefficients of a bivariate polynomial that generalizes both the length and the reflection length generating functions for finite Coxeter groups, Petersen introduced a new Mahonian statistic $sor$, called the sorting index. Petersen proved that the pairs of statistics $(sor,cyc)$ and $(inv,rl\textrm{-}min)$ have the same joint distribution over the symmetric group, and asked for a combinatorial proof of this fact. In answer to the question of Petersen, we observe a connection between the sorting index and the B-code of a permutation defined by Foata and Han, and we show that the bijection of Foata and Han serves the purpose of mapping $(inv,rl\textrm{-}min)$ to $(sor,cyc)$. We also give a type $B$ analogue of the Foata-Han bijection, and we derive the quidistribution of $(inv_B,{\rm Lmap_B},{\rm Rmil_B})$ and $(sor_B,{\rm Lmap_B},{\rm Cyc_B})$ over signed permutations. So we get a combinatorial interpretation of Petersen's equidistribution of $(inv_B,nmin_B)$ and $(sor_B,l_B')$. Moreover, we show that the six pairs of set-valued statistics $\rm (Cyc_B,Rmil_B)$, $\rm(Cyc_B,Lmap_B)$, $\rm(Rmil_B,Lmap_B)$, $\rm(Lmap_B,Rmil_B)$, $\rm(Lmap_B,Cyc_B)$ and $\rm(Rmil_B,Cyc_B)$ are equidistributed over signed permutations. For Coxeter groups of type $D$, Petersen showed that the two statistics $inv_D$ and $sor_D$ are equidistributed. We introduce two statistics $nmin_D$ and $\tilde{l}_D'$ for elements of $D_n$ and we prove that the two pairs of statistics $(inv_D,nmin_D)$ and $(sor_D,\tilde{l}_D')$ are equidistributed.Comment: 25 page

Direct laser acceleration of electrons assisted by strong laser-driven azimuthal plasma magnetic fields.

A high-intensity laser beam propagating through a dense plasma drives a strong current that robustly sustains a strong quasistatic azimuthal magnetic field. The laser field efficiently accelerates electrons in such a field that confines the transverse motion and deflects the electrons in the forward direction. Its advantage is a threshold rather than resonant behavior, accelerating electrons to high energies for sufficiently strong laser-driven currents. We study the electron dynamics via a test-electron model, specifically deriving the corresponding critical current density. We confirm the model's predictions by numerical simulations, indicating energy gains two orders of magnitude higher than achievable without the magnetic field