Alternative Canonical Formalism for the Wess-Zumino-Witten Model

We study a canonical quantization of the Wess--Zumino--Witten (WZW) model which depends on two integer parameters rather than one. The usual theory can be obtained as a contraction, in which our two parameters go to infinity keeping the difference fixed. The quantum theory is equivalent to a generalized Thirring model, with left and right handed fermions transforming under different representations of the symmetry group. We also point out that the classical WZW model with a compact target space has a canonical formalism in which the current algebra is an affine Lie algebra of non--compact type. Also, there are some non--unitary quantizations of the WZW model in which there is invariance only under half the conformal algebra (one copy of the Virasoro algebra).Comment: 22 pages; UR-133

Machine-learning nonstationary noise out of gravitational-wave detectors

Signal extraction out of background noise is a common challenge in high-precision physics experiments, where the measurement output is often a continuous data stream. To improve the signal-to-noise ratio of the detection, witness sensors are often used to independently measure background noises and subtract them from the main signal. If the noise coupling is linear and stationary, optimal techniques already exist and are routinely implemented in many experiments. However, when the noise coupling is nonstationary, linear techniques often fail or are suboptimal. Inspired by the properties of the background noise in gravitational wave detectors, this work develops a novel algorithm to efficiently characterize and remove nonstationary noise couplings, provided there exist witnesses of the noise source and of the modulation. In this work, the algorithm is described in its most general formulation, and its efficiency is demonstrated with examples from the data of the Advanced LIGO gravitational-wave observatory, where we could obtain an improvement of the detector gravitational-wave reach without introducing any bias on the source parameter estimation

Interdependencies between financial and non-financial performances: a holistic and short-term analytical perspective

Purpose: This paper aims to investigate possible interdependencies affecting short-term profitability between internal and process business aspects which can play a critical role in sustainability operationalisation. Design/methodology/approach: The authors adopted the panel data approach to perform a partial least square structural modelling equation analysis on a sample of 391 Organisation for Economic Co-operation and Development (OECD) non-financial-listed companies, considering a timeframe of five years. Findings: Corporate sustainability is a result of interplays between managerial commitment, strategy, slack resources’ exploitation, innovation, the sustainable management of internal production and procurement processes that managers can catalyse to foster short-term firms’ profitability. Research limitations/implications: The study is focused on internal process business determinants of sustainability, and the analysis is limited to a short-term timeframe and on non-financial OECD-listed companies. Practical implications: Managers searching for trade-offs between financial and non-financial performances should enhance their commitment towards sustainability by defining appropriate strategies suitable to employ mainly slack resources derived from core business activities enabling innovation processes, which, in turn, are able to foster sustainability of internal production and procurement processes. Originality/value: The execution of sustainability is a complex process that needs to be investigated using a holistic approach net of endogeneity biases to better appreciate those interrelationships within multiple drivers determining the firm sustainable growth

Analysing the role of available organisational slack resources in affecting environmental performance. A structural equation modelling approach

PURPOSE: This paper aims to investigate the relationships between business slack resources and environmental performance and considers the possible effects that management commitment, corporate strategy to sustainability and innovation intensity can have on such interactions. DESIGN/METHODOLOGY/APPROACH: We performed partial least squares path modeling regressions on a sample of 697 non-financial listed companies worldwide, considering a time frame of 13 years. FINDINGS: Operational and financial slack resources are both detrimental to environmental performance in the short term. Nevertheless, financial slack resources are useful to boost innovation that enhances environmental performance. Environmental performance improvement seems to be more a matter of managerial commitment and strategic approach towards sustainability, rather than the availability of slack resources. RESEARCH LIMITATIONS/IMPLICATIONS: Due to literature shortcomings on which effects slack resources can have on environmental performance, this paper sheds some light on the topic while also highlighting the role of management commitment, corporate sustainability strategy and innovation. PRACTICAL IMPLICATIONS: Managers should use financial slack resources in innovation activities to improve environmental performance. In doing so, they need to create retaining earnings to offset any costs using financial slack resources. ORIGINALITY/VALUE: Adopting a holistic and net of endogeneity analytical perspective, this paper highlights some virtuous and critical interactions between the managerial commitment and strategic approach to sustainability, the availability of slack resources, innovation intensity and environmental performance to understand which aspects may foster or hinder the ecological transition of businesses

Thermal gradient-induced forces on geodetic reference masses for LISA

The low frequency sensitivity of space-borne gravitational wave observatories will depend critically on the geodetic purity of the trajectories of orbiting test masses. Fluctuations in the temperature difference across the enclosure surrounding the free-falling test mass can produce noisy forces through several processes, including the radiometric effect, radiation pressure, and outgassing. We present here a detailed experimental investigation of thermal gradient-induced forces for the LISA gravitational wave mission and the LISA Pathfinder, employing high resolution torsion pendulum measurements of the torque on a LISA-like test mass suspended inside a prototype of the LISA gravitational reference sensor that will surround the test mass in orbit. The measurement campaign, accompanied by numerical simulations of the radiometric and radiation pressure effects, allows a more accurate and representative characterization of thermal-gradient forces in the specific geometry and environment relevant to LISA free-fall. The pressure dependence of the measured torques allows clear identification of the radiometric effect, in quantitative agreement with the model developed. In the limit of zero gas pressure, the measurements are most likely dominated by outgassing, but at a low level that does not threaten the LISA sensitivity goals.Comment: 21 pages, 16 figures, submitted to Physical Review

A robust data cleaning procedure for eddy covariance flux measurements

Abstract. The sources of systematic error responsible for introducing significant biases in the eddy covariance (EC) flux computation are manifold, and their correct identification is made difficult by the lack of reference values, by the complex stochastic dynamics, and by the high level of noise characterizing raw data. This work contributes to overcoming such challenges by introducing an innovative strategy for EC data cleaning. The proposed strategy includes a set of tests aimed at detecting the presence of specific sources of systematic error, as well as an outlier detection procedure aimed at identifying aberrant flux values. Results from tests and outlier detection are integrated in such a way as to leave a large degree of flexibility in the choice of tests and of test threshold values, ensuring scalability of the whole process. The selection of best performing tests was carried out by means of Monte Carlo experiments, whereas the impact on real data was evaluated on data distributed by the Integrated Carbon Observation System (ICOS) research infrastructure. Results evidenced that the proposed procedure leads to an effective cleaning of EC flux data, avoiding the use of subjective criteria in the decision rule that specifies whether to retain or reject flux data of dubious quality. We expect that the proposed data cleaning procedure can serve as a basis towards a unified quality control strategy for EC datasets, in particular in centralized data processing pipelines where the use of robust and automated routines ensuring results reproducibility constitutes an essential prerequisite

Torsion pendulum facility for direct force measurements of LISA GRS related disturbances

A four mass torsion pendulum facility for testing of the LISA GRS is under development in Trento. With a LISA-like test mass suspended off-axis with respect to the pendulum fiber, the facility allows for a direct measurement of surface force disturbances arising in the GRS. We present here results with a prototype pendulum integrated with very large-gap sensors, which allows an estimate of the intrinsic pendulum noise floor in the absence of sensor related force noise. The apparatus has shown a torque noise near to its mechanical thermal noise limit, and would allow to place upper limits on GRS related disturbances with a best sensitivity of 300 fN/Hz^(1/2) at 1mHz, a factor 50 from the LISA goal. Also, we discuss the characterization of the gravity gradient noise, one environmental noise source that could limit the apparatus performances, and report on the status of development of the facility.Comment: Submitted to Proceedings of the 6th International LISA Symposium, AIP Conference Proceedings 200