المؤلفون: Ulgiati, Alberto, Vincentelli, Federico Maria, Casella, Piergiorgio, Veledina, Alexandra, Maccarone, Thomas, Russell, David, Uttley, Phil, Ambrosino, Filippo, Baglio, Maria Cristina, Imbrogno, Matteo, Melandri, Andrea, Motta, Sara Elisa, O'Brien, Kiran, Sanna, Andrea, Shahbaz, Tariq, Altamirano, Diego, Fender, Rob, Maitra, Dipankar, Malzac, Julien

مصطلحات موضوعية: Astrophysics - High Energy Astrophysical Phenomena

الوصف: We report on two epochs of simultaneous near-infrared (IR) and X-ray observations with a sub-second time resolution of the low mass X-ray binary black hole candidate Swift J1753.5--0127 during its long 2005--2016 outburst. Data were collected strictly simultaneously with VLT/ISAAC (K$_{S}$ band, 2.2 $\mu m$) and RXTE (2-15 keV) or \textit{XMM-Newton} (0.7-10 keV). A clear correlation between the X-ray and the IR variable emission is found during both epochs but with very different properties. In the first epoch, the near-IR variability leads the X-ray by $ \sim 130 \, ms$. This is the opposite of what is usually observed in similar systems. The correlation is more complex in the second epoch, with both anti-correlation and correlations at negative and positive lags. Frequency-resolved Fourier analysis allows us to identify two main components in the complex structure of the phase lags: the first component, characterised by a few seconds near-IR lag at low frequencies, is consistent with a combination of disc reprocessing and a magnetised hot flow; the second component is identified at high frequencies by a near-IR lag of $\approx$0.7 s. Given the similarities of this second component with the well-known constant optical/near-IR jet lag observed in other black hole transients, we tentatively interpret this feature as a signature of a longer-than-usual jet lag. We discuss the possible implications of measuring such a long jet lag in a radio-quiet black hole transient.
Comment: 10 pages, 7 figures, accepted for publication in A&A

الوصول الحر: http://arxiv.org/abs/2407.00195Test

المؤلفون: Maitra, Sarit

مصطلحات موضوعية: Mathematics - Optimization and Control

الوصف: This study presents a comprehensive approach to optimizing inventory management under stochastic demand by leveraging Monte Carlo Simulation (MCS) with grid search and Bayesian optimization. By using a business case of historical demand data and through the comparison of periodic review (p, Q) and continuous review (r, Q) inventory policies, it demonstrates that the (r, Q) policy significantly increases expected profit by dynamically managing inventory levels based on daily demand and lead time considerations. The integration of random and conditional sampling techniques highlights critical periods of high demand, providing deeper insights into demand patterns. While conditional sampling reduces execution time, it yields slightly lower profits compared to random sampling. Though Bayesian optimization marginally outperforms grid search in identifying optimal reorder quantities and points, however, given the stochastic nature of the algorithm, this can change with multiple runs. This study accentuates the effectiveness of advanced simulation and optimization techniques in addressing complex inventory challenges, ultimately supporting more informed and profitable inventory management decisions. The simulation model and optimization framework are open-source and written in Python, promoting transparency and enabling other researchers and practitioners to replicate and build upon this work. This contributes to the advancement of knowledge and the development of more effective inventory management solutions.

الوصول الحر: http://arxiv.org/abs/2406.19425Test

المؤلفون: Maitra, Bitop, Akan, Ozgur B.

مصطلحات موضوعية: Quantitative Biology - Neurons and Cognition, Quantum Physics

الوصف: The gut-brain axis is the communication link between the gut and the brain. Although it is known that the gut-brain axis plays a pivotal role in homeostasis, its overall mechanism is still not known. However, for neural synapses, classical molecular communication is described by the formation of ligand-receptor complexes, which leads to the opening of ion channels. Moreover, there are some conditions that need to be fulfilled before the opening of the ion channel. In this study, we will consider the gut-brain axis, where neurotransmitters diffuse through the synaptic cleft, considering molecular communication. On the vagus nerve (VN) membrane, i.e., the post-synaptic membrane of the synapse, it undergoes a quantum communication (QC), which initiates the opening of the ion channel, thus initiating the communication signal from the gut to the brain. It evolves a new paradigm of communication approach, Molecular Quantum (MolQ) communication. Based on the QC model, we theoretically analyzes the output states, and QC is simulated considering the incoming neurotransmitter's concentration and validated by analyzing the entropy and the mutual information of the input, i.e., neurotransmitter's concentration, and output, i.e., ion channel opening.
Comment: 7 pages

الوصول الحر: http://arxiv.org/abs/2407.07106Test

المؤلفون: Chandel, Vikramjeet Singh, Gorai, Sushil, Maitra, Anwoy, Sarkar, Amar Deep

مصطلحات موضوعية: Mathematics - Complex Variables, Mathematics - Metric Geometry, Primary: 32F45, 30D40, Secondary: 32Q45, 53C23

الوصف: In this paper we report our investigations on visibility with respect to the Kobayashi distance and its applications, with a special focus on planar domains. We prove that totally disconnected subsets of the boundary are removable in the context of visibility. We also show that a domain in $\mathbb{C}^n$ is a local weak visibility domain if and only if it is a weak visibility domain. The above holds also for visibility. Along the way, we prove an intrinsic localization result for the Kobayashi distance. Moreover, we observe some interesting consequences of weak visibility; for example, weak visibility implies compactness of the end topology of the closure of the domain. For planar domains: (i) We provide examples of visibility domains that are not locally Goldilocks at any boundary point. (ii) We provide certain general conditions on planar domains that yield the continuous extension of conformal maps, generalizing the Carath\'{e}odory extension theorem. Our conditions are quite general and assume very little regularity of the boundary. We demonstrate this through examples. (iii) We also provide conditions for the homeomorphic extension of biholomorphic maps up to the boundary. (iv) We prove that a hyperbolic, simply connected domain possesses the visibility property if and only if its boundary is locally connected. This leads us to reformulate the MLC conjecture in terms of visibility. (v) We provide a characterization of visibility for a large class of planar domains including certain uncountably connected domains.
Comment: 66 pages. Comments are welcome

الوصول الحر: http://arxiv.org/abs/2406.15298Test

المؤلفون: Bhardwaj, Srishti, Maitra, T.

مصطلحات موضوعية: Condensed Matter - Materials Science

الوصف: The coexistence of seemingly mutually exclusive properties such as ferromagnetism, ferroelectricity and metallicity in atomically thin materials is the requirement of the hour in electronics as the Moore's law faces an impending end. Only a few 2D multiferroic materials have been predicted/realized so far. The polar metals with simultaneous presence of polarity and conductivity are also equally rare. Here, we predict, based on first-principles calculations that an Eu-substituted rare-earth halide GdI$_2$ monolayer showcases ferromagnetism, ferroelasticity while being polar and a fully spin-polarized semi-metal at the same time. The ferroelasticity and polarity are shown to be coupled making it possible to switch the polar direction using external mechanical stress. Further, it is observed that, an application of biaxial tensile strain of $5\%$ causes the spin easy-axis to shift from out-of-plane to in-plane direction. Thus spin easy axis gets coupled with the direction of polarization in the strained monolayer making the switching of magnetization also possible using external strain. Simultaneous coexistence and coupling of the ferroic orders in a metallic 2D material makes the Eu substituted GdI$_2$ monolayer an incredibly rare material for nano-electronics and spintronics applications.
Comment: 7 pages, 5 figures

الوصول الحر: http://arxiv.org/abs/2406.04122Test

المؤلفون: van der Hofstad, Remco, van der Hoorn, Pim, Kerriou, Céline, Maitra, Neeladri, Mörters, Peter

مصطلحات موضوعية: Mathematics - Probability

الوصف: We identify the upper large deviation probability for the number of edges in scale-free geometric random graph models as the space volume goes to infinity. Our result covers the models of scale-free percolation, the Boolean model with heavy-tailed radius distribution, and the age-dependent random connection model. In all these cases the mechanism behind the large deviation is based on a condensation effect. Loosely speaking, the mechanism randomly selects a finite number of vertices and increases their power, so that they connect to a macroscopic number of vertices in the graph, while the other vertices retain a degree close to their expectation and thus make no more than the expected contribution to the large deviation event. We verify this intuition by means of limit theorems for the empirical distributions of degrees and edge-lengths under the conditioning. We observe that at large finite volumes, the edge-length distribution splits into a bulk and travelling wave part of asymptotically positive proportions.
Comment: 45 pages, one figure

الوصول الحر: http://arxiv.org/abs/2405.20425Test

المؤلفون: Maitra, Matthew, Tromp, Jeroen

مصطلحات موضوعية: General Relativity and Quantum Cosmology, Physics - Geophysics

الوصف: The weak-field limit of Einstein--Cartan (EC) relativity is studied. The equations of EC theory are rewritten such that they formally resemble those of Einstein General Relativity (EGR); this allows ideas from post-Newtonian theory to be imported without essential change. The equations of motion are then written both at first post-Newtonian (1PN) order and at 1.5PN order. EC theory's 1PN equations of motion are found to be those of a micropolar/Cosserat elastic medium, along with a decoupled evolution equation for non-classical, spin-related fields. It seems that a necessary condition for these results to hold is that one chooses the non-classical fields to scale with the speed of light in a certain empirically reasonable way. Finally, the 1.5PN equations give greater insight into the coupling between energy-momentum and spin within slowly moving, weakly gravitating matter. Specifically, the weakly relativistic modifications to Cosserat theory involve a gravitational torque and an augmentation of the gravitational force due to a `dynamic mass moment density' with an accompanying `dynamic mass moment density flux', and new forms of linear momentum density captured by a `dynamic mass density flux' and a `dynamic momentum density'.

الوصول الحر: http://arxiv.org/abs/2405.12188Test

المؤلفون: Carli, E., Levin, L., Stappers, B. W., Barr, E. D., Breton, R. P., Buchner, S., Burgay, M., Geyer, M., Kramer, M., Padmanabh, P. V., Possenti, A., Krishnan, V. Venkatraman, Becker, W., Filipović, M. D., Maitra, C., Behrend, J., Champion, D. J., Chen, W., Men, Y. P., Ridolfi, A.

مصطلحات موضوعية: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Astrophysics of Galaxies

الوصف: The sensitivity of the MeerKAT radio interferometer is an opportunity to probe deeper into the population of rare and faint extragalactic pulsars. The TRAPUM (TRAnsients and PUlsars with MeerKAT) collaboration has conducted a radio-domain search for accelerated pulsars and transients in the Small Magellanic Cloud (SMC). This partially targeted survey, performed at L-band (856-1712 MHz) with the core array of the MeerKAT telescope in 2-h integrations, is twice as sensitive as the latest SMC radio pulsar survey. We report the discovery of seven new SMC pulsars, doubling this galaxy's radio pulsar population and increasing the total extragalactic population by nearly a quarter. We also carried out a search for accelerated millisecond pulsars in the SMC Globular Cluster NGC 121 using the full array of MeerKAT. This improved the previous upper limit on pulsed radio emission from this cluster by a factor of six. Our discoveries reveal the first radio pulsar-PWN systems in the SMC, with only one such system previously known outside our galaxy (the "Crab pulsar twin" in the Large Magellanic Cloud, PSR J0540$-$6919). We associate the 59 ms pulsar discovery PSR J0040$-$7337, now the fastest spinning radio pulsar in the SMC, with the bow-shock Pulsar Wind Nebula (PWN) of Supernova Remnant DEM S5. We also present a new young pulsar with a 79 ms period, PSR J0048$-$7317, in a PWN recently discovered in a MeerKAT radio continuum image. Using the multi-beam capability of MeerKAT, we localised our pulsar discoveries, and two previous Murriyang discoveries, to a positional uncertainty of a few arcseconds.
Comment: 32 pages, 14 figures, 10 tables. Accepted for publication in Monthly Notices of the Royal Astronomical Society

الوصول الحر: http://arxiv.org/abs/2405.12029Test

المؤلفون: Wood, Callan M., Miller-Jones, James C. A., Bahramian, Arash, Tingay, Steven J., Prabu, Steve, Russell, Thomas D., Atri, Pikky, Carotenuto, Francesco, Altamirano, Diego, Motta, Sara E., Hyland, Lucas, Reynolds, Cormac, Weston, Stuart, Fender, Rob, Körding, Elmar, Maitra, Dipankar, Markoff, Sera, Migliari, Simone, Russell, David M., Sarazin, Craig L., Sivakoff, Gregory R., Soria, Roberto, Tetarenko, Alexandra J., Tudose, Valeriu

مصطلحات موضوعية: Astrophysics - High Energy Astrophysical Phenomena

الوصف: Multi-wavelength polarimetry and radio observations of Swift J1727.8-1613 at the beginning of its recent 2023 outburst suggested the presence of a bright compact jet aligned in the north-south direction, which could not be confirmed without high angular resolution images. Using the Very Long Baseline Array and the Long Baseline Array, we imaged Swift J1727.8-1613, during the hard/hard-intermediate state, revealing a bright core and a large, two-sided, asymmetrical, resolved jet. The jet extends in the north-south direction, at a position angle of $-0.60\pm0.07\deg$ East of North. At 8.4 GHz, the entire resolved jet structure is $\sim110 (d/2.7\,\text{kpc})/\sin i$ AU long, with the southern approaching jet extending $\sim80 (d/2.7\,\text{kpc})/\sin i$ AU from the core, where $d$ is the distance to the source and $i$ is the inclination of the jet axis to the line of sight. These images reveal the most resolved continuous X-ray binary jet, and possibly the most physically extended continuous X-ray binary jet ever observed. Based on the brightness ratio of the approaching and receding jets, we put a lower limit on the intrinsic jet speed of $\beta\geq0.27$ and an upper limit on the jet inclination of $i\leq74\deg$. In our first observation we also detected a rapidly fading discrete jet knot $66.89\pm0.04$ mas south of the core, with a proper motion of $0.66\pm0.05$ mas hour$^{-1}$, which we interpret as the result of a downstream internal shock or a jet-ISM interaction, as opposed to a transient relativistic jet launched at the beginning of the outburst.
Comment: Submitted to ApJL

الوصول الحر: http://arxiv.org/abs/2405.12370Test

المؤلفون: Maitra, Sarit

مصطلحات موضوعية: Computer Science - Machine Learning

الوصف: Building operations consume 30% of total power consumption and contribute 26% of global power-related emissions. Therefore, monitoring, and early detection of anomalies at the meter level are essential for residential and commercial buildings. This work investigates both supervised and unsupervised approaches and introduces a dynamic anomaly detection system. The system introduces a supervised Light Gradient Boosting machine and an unsupervised autoencoder with a dynamic threshold. This system is designed to provide real-time detection of anomalies at the meter level. The proposed dynamical system comes with a dynamic threshold based on the Mahalanobis distance and moving averages. This approach allows the system to adapt to changes in the data distribution over time. The effectiveness of the proposed system is evaluated using real-life power consumption data collected from smart metering systems. This empirical testing ensures that the system's performance is validated under real-world conditions. By detecting unusual data movements and providing early warnings, the proposed system contributes significantly to visual analytics and decision science. Early detection of anomalies enables timely troubleshooting, preventing financial losses and potential disasters such as fire incidents.

الوصول الحر: http://arxiv.org/abs/2405.02574Test