Parity breaking signatures from a Chern-Simons coupling during inflation: the case of non-Gaussian gravitational waves

Considering high-energy modifications of Einstein gravity during inflation is an interesting issue. We can constrain the strength of the new gravitational terms through observations of inflationary imprints in the actual universe. In this paper we analyze the effects on slow-roll models due to a Chern-Simons term coupled to the inflaton field through a generic coupling function $f(\phi)$. A well known result is the polarization of primordial gravitational waves (PGW) into left and right eigenstates, as a consequence of parity breaking. In such a scenario the modifications to the power spectrum of PGW are suppressed under the conditions that allow to avoid the production of ghost gravitons at a certain energy scale, the so-called Chern-Simons mass $M_{CS}$. In general it has been recently pointed out that there is very little hope to efficiently constrain chirality of PGW on the basis solely of two-point statistics from future CMB data, even in the most optimistic cases. Thus we search if significant parity breaking signatures can arise at least in the bispectrum statistics. We find that the tensor-tensor-scalar bispectra $\langle \gamma \gamma \zeta \rangle$ for each polarization state are the only ones that are not suppressed. Their amplitude, setting the level of parity breaking during inflation, is proportional to the second derivative of the coupling function $f(\phi)$ and they turn out to be maximum in the squeezed limit. We comment on the squeezed-limit consistency relation arising in the case of chiral gravitational waves, and on possible observables to constrain these signatures.Comment: 31 pages, 1 figure. V3: references added; typos correcte

Market Equilibrium in the Presence of Green Consumers and Responsible Firms: a Comparative Statics Analysis

This paper analyzes how the interaction between green consumers and responsible firms affects the market equilibrium. The main result is that a higher responsibility by both producers and consumers can have different impacts on the efficiency of the firms' abatement activity, depending on the nature of the cleaning costs. When the abatement costs are fixed, the efficiency of the clean-up effort is always increasing in their degree of responsibility. On the other hand, when the abatement costs are variable, a higher level of responsibility may reduce social welfare. Finally, the first best allocation is never reached, even in the presence of the highest credible level of responsibility of both consumers and producers.Green Consumers, Corporate Social Responsibility, Vertical Differentiation

Market Equilibrium in the Presence of Green Consumers and Responsible Firms: A Comparative Statics Analysis

This paper analyzes how the interaction between green consumers and responsible firms affects the market equilibrium. The main result is that a higher responsibility by both producers and consumers can have different impacts on the efficiency of the firms’ abatement activity, depending on the nature of the cleaning costs. When the abatement costs are fixed, the efficiency of the clean-up effort is always increasing in their degree of responsibility. On the other hand, when the abatement costs are variable, a higher level of responsibility may reduce social welfare. Finally, the first best allocation is never reached, even in the presence of the highest credible level of responsibility of both consumers and producers.Green Consumers, Corporate Social Responsibility, Vertical Differentiation

Measuring chiral gravitational waves in Chern-Simons gravity with CMB bispectra

Chern-Simons gravity coupled to the scalar sector through a generic coupling function $f(\phi)$ can be tested at the very high energies of the inflationary period. In 1706.04627, we computed the theoretical parity breaking signatures of the $\langle \gamma \gamma \zeta \rangle$ primordial bispectrum which mixes two gravitons and one scalar curvature perturbation. We defined a parameter $\Pi$ which measures the level of parity breaking of the corresponding bispectrum. In this work we forecast the expected $1 \sigma$ error on $\Pi$ using the cosmic microwave background (CMB) angular bispectra. We find that, given the angular resolution of an experiment like $Planck$, $\Pi \sim 10^6$ is detectable via the measurement of $BBT$ or $BBE$ angular bispectra if the tensor-to-scalar ratio $r = 0.01$. We also show that, from the theoretical point of view, $\Pi$ can be greater than $10^6$. Thus, our conclusion is that $BBT$ or $BBE$ CMB angular bispectra can become an essential observable for testing Chern-Simons gravity in the primordial universe.Comment: 16 pages, 1 figure; version matching publication in JCA

Competitive reaction modelling in aqueous systems. The case of contemporary reduction of dichromates and nitrates by nZVI

In various Countries, Cr(VI) still represents one of the groundwater pollutant of major concern, mainly due to its high toxicity, furthermore enhanced by the synergic effect in presence of other contaminants. As widely reported in the recent literature, nanoscale zero valent iron particles (nZVI-p) have been proved to be particularly effective in the removal of a wide range of contaminants from polluted waters. In this work, experimental tests of hexavalent chromium reduction in polluted groundwater in the presence of nitrate by nZVI-p are presented and discussed. The effect of different nitrate amounts on Cr(VI) reduction mechanism was investigated and the obtained results were successfully interpreted by the proposed kinetic model. nZVI-p produced by the classical borohydride reduction method were added in to synthetic solutions with the initial concentration of Cr(VI) set at 93, 62 and 31 mg L-1 and different nitrate contents in the range 10-100 mg L-1. According to the experimental results, nitrate showed an adverse effect on Cr(VI) reduction, depending on the nZVI/Cr(VI) and Cr(VI)/NO3 - ratio. The proposed kinetic model soundly grasps the competitive nature of the Cr(VI) reduction process when other chemical species are present in the treated solution

Production of nano zero valent iron particles by means of a spinning disk reactor

Nitrates are considered hazard compounds for human health due to their tendency to be reduced to nitrites, in particular in reducing environment. Nano zero valent iron (nZVI) represents an efficient and low-cost adsorbent/reductive agent for nitrate removal from groundwater. In this work, nZVI particles were produced by means of two different equipment types based on the same chemical synthesis method: a batch stirred tank reactor (BSTR) and a spinning disk reactor (SDR). This latter apparatus is capable to strongly promote micromixing at a steady-state, continuous condition, and such as qualifies to subsist in the framework of process intensification. Particle size distribution (PSD) of the obtained nZVI particles were measured by a DLS technique. The removal efficiency of the produced nVI particles were checked by using two NO3-solutions (1.6 and 6.4 mM) and by monitoring nitrate concentration reduction rates at selected time intervals. Results showed that the nZVI particles produced by SDR have a narrow PSD with a mean diameter of 65nm; on the contrary, particles produced by BSTR shows bimodal PSD with modal sizes of 105 nm and 400 nm, respectively. Experimental tests of nitrates reduction in water have been performed, using both the particles produced by the above mentioned techniques. Results of batch tests showed that the highest removal efficiency of nitrates was observed by using the nZVI particles produced by means of SDR, as a consequence of the higher average specific surface. Since nitrate removal process involves both reduction and adsorption processes, the removal mechanism has been investigated, and the pseudo-first-order reduction kinetic model was successfully tested and reported in both cases

Co-manipulation of soft-materials estimating deformation from depth images

Human-robot co-manipulation of soft materials, such as fabrics, composites, and sheets of paper/cardboard, is a challenging operation that presents several relevant industrial applications. Estimating the deformation state of the co-manipulated material is one of the main challenges. Viable methods provide the indirect measure by calculating the human-robot relative distance. In this paper, we develop a data-driven model to estimate the deformation state of the material from a depth image through a Convolutional Neural Network (CNN). First, we define the deformation state of the material as the relative roto-translation from the current robot pose and a human grasping position. The model estimates the current deformation state through a Convolutional Neural Network, specifically a DenseNet-121 pretrained on ImageNet.The delta between the current and the desired deformation state is fed to the robot controller that outputs twist commands. The paper describes the developed approach to acquire, preprocess the dataset and train the model. The model is compared with the current state-of-the-art method based on a skeletal tracker from cameras. Results show that our approach achieves better performances and avoids the various drawbacks caused by using a skeletal tracker.Finally, we also studied the model performance according to different architectures and dataset dimensions to minimize the time required for dataset acquisitionComment: Pre-print, submitted to Journal of Intelligent Manufacturin

Transcriptome dynamics in the asexual cycle of the chordate Botryllus schlosseri

Background: We performed an analysis of the transcriptome during the blastogenesis of the chordate Botryllus schlosseri, focusing in particular on genes involved in cell death by apoptosis. The tunicate B. schlosseri is an ascidian forming colonies characterized by the coexistence of three blastogenetic generations: filter-feeding adults, buds on adults, and budlets on buds. Cyclically, adult tissues undergo apoptosis and are progressively resorbed and replaced by their buds originated by asexual reproduction. This is a feature of colonial tunicates, the only known chordates that can reproduce asexually. Results: Thanks to a newly developed web-based platform (http://botryllus.cribi.unipd.it), we compared the transcriptomes of the mid-cycle, the pre-take-over, and the take-over phases of the colonial blastogenetic cycle. The platform is equipped with programs for comparative analysis and allows to select the statistical stringency. We enriched the genome annotation with 11,337 new genes; 581 transcripts were resolved as complete open reading frames, translated in silico into amino acid sequences and then aligned onto the non-redundant sequence database. Significant differentially expressed genes were classified within the gene ontology categories. Among them, we recognized genes involved in apoptosis activation, de-activation, and regulation. Conclusions: With the current work, we contributed to the improvement of the first released B. schlosseri genome assembly and offer an overview of the transcriptome changes during the blastogenetic cycle, showing up- and down-regulated genes. These results are important for the comprehension of the events underlying colony growth and regression, cell proliferation, colony homeostasis, and competition among different generations

Photon-graviton scattering: A new way to detect anisotropic gravitational waves?

Gravitons are the quantum counterparts of gravitational waves in low-energy theories of gravity. Using Feynman rules one can compute scattering amplitudes describing the interaction between gravitons and other fields. Here, we consider the interaction between gravitons and photons. Using the quantum Boltzmann equation formalism, we derive fully general equations describing the radiation transfer of photon polarization, due to the forward scattering with gravitons. We show that the Q and U photon linear polarization modes couple with the V photon circular polarization mode, if gravitons have anisotropies in their power-spectrum statistics. As an example, we apply our results to the case of primordial gravitons, considering models of inflation where an anisotropic primordial graviton distribution is produced. Finally, we evaluate the effect on cosmic microwave background (CMB) polarization, showing that in general the expected effects on the observable CMB frequencies are very small. However, our result is promising, since it could provide a novel tool for detecting anisotropic backgrounds of gravitational waves, as well as for getting further insight on the physics of gravitational waves.Comment: 15 pages, 1 figure. v2: references added, typos corrected, replaced to match published version in PR