Localization in fractonic random circuits

We study the spreading of initially-local operators under unitary time evolution in a 1d random quantum circuit model which is constrained to conserve a $U(1)$ charge and its dipole moment, motivated by the quantum dynamics of fracton phases. We discover that charge remains localized at its initial position, providing a crisp example of a non-ergodic dynamical phase of random circuit dynamics. This localization can be understood as a consequence of the return properties of low dimensional random walks, through a mechanism reminiscent of weak localization, but insensitive to dephasing. The charge dynamics is well-described by a system of coupled hydrodynamic equations, which makes several nontrivial predictions in good agreement with numerics. Importantly, these equations also predict localization in 2d fractonic circuits. Immobile fractonic charge emits non-conserved operators, whose spreading is governed by exponents distinct to non-fractonic circuits. Fractonic operators exhibit a short time linear growth of observable entanglement with saturation to an area law, as well as a subthermal volume law for operator entanglement. The entanglement spectrum follows semi-Poisson statistics, similar to eigenstates of MBL systems. The non-ergodic phenomenology persists to initial conditions containing non-zero density of dipolar or fractonic charge. Our work implies that low-dimensional fracton systems preserve forever a memory of their initial conditions in local observables under noisy quantum dynamics, thereby constituting ideal memories. It also implies that 1d and 2d fracton systems should realize true MBL under Hamiltonian dynamics, even in the absence of disorder, with the obstructions to MBL in translation invariant systems and in d>1 being evaded by the nature of the mechanism responsible for localization. We also suggest a possible route to new non-ergodic phases in high dimensions.Comment: Appended erratu

Bose-Hubbard Models in Confining Potentials: An Inhomogeneous Mean-Field Theory

We present an extensive study of Mott insulator (MI) and superfluid (SF) shells in Bose-Hubbard (BH) models for bosons in optical lattices with harmonic traps. For this we develop an inhomogeneous mean-field theory. Our results for the BH model with one type of spinless bosons agrees quantitatively with quantum Monte Carlo (QMC) simulations. Our approach is numerically less intensive than such simulations, so we are able to perform calculation on experimentally realistic, large 3D systems, explore a wide range of parameter values, and make direct contact with a variety of experimental measurements. We also generalize our inhomogeneous mean-field theory to study BH models with harmonic traps and (a) two species of bosons or (b) spin-1 bosons. With two species of bosons we obtain rich phase diagrams with a variety of SF and MI phases and associated shells, when we include a quadratic confining potential. For the spin-1 BH model we show, in a representative case, that the system can display alternating shells of polar SF and MI phases; and we make interesting predictions for experiments in such systems.Comment: 17 pages, 18 figure

Phases and transitions in the spin-1 Bose-Hubbard model: systematics of a mean-field theory

We generalize the mean-field theory for the spinless Bose-Hubbard model to account for the different types of superfluid phases that can arise in the spin-1 case. In particular, our mean-field theory can distinguish polar and ferromagnetic superfluids, Mott insulator, that arise at integer fillings at zero temperature, and normal Bose liquids into which the Mott insulators evolve at finite temperatures. We find, in contrast to the spinless case, that several of the superfluid-Mott insulator transitions are of first order at finite temperatures. Our systematic study yields rich phase diagrams that include first-order and second-order transitions and a variety of tricritical points. We discuss the possibility of realizing such phase diagrams in experimental systems

Iron-oxide based electrodes in aqueous supercapacitors

Climate change and the limited availability of fossil fuels have greatly affected the world economy and ecology. The demand of energy is not coping up the supply of the same. With a fast-growing market for portable electronic devices and the development of hybrid electric vehicles, there has been an ever increasing and urgent demand for environmentally friendly high-power energy resources. This has led to development of energy storage devices, mostly supercapacitors and batteries. In the recent times it is seen that li-ion batteries have been dominating energy storage device sector (Portable electronics, hybrid vehicles and grids). Li-ion still lacks when there is sudden demand in high power. The development of higher energy and power density systems highly rely upon the advancement of new materials used in these devices. Transition oxides and conducting polymers based nanofibers are excellent candidates for application as electrodes in the energy storage devices because of their unique properties such as high capacitance, chemical durability, nature friendly and high specific surface area. Electrospinning is a simple, fast and a scalable technique wherein fiber formation is done with the help of a strong electric field to stretch out a polymer solution to form nanofibers with diameters in the range of 100-800 nm. This fiber-formation technique results in formation of free-standing, binder free and non-woven fiber mat. My thesis focuses on preparation of Iron oxide based nanofibers through electrospinning method, characterizing these nanofibers via spectroscopic/microscopic techniques and developing understanding of their electrochemical mechanisms in an aqueous medium. My work focusses more on structurally supporting these oxides in the conductive carbon fiber matrix which otherwise delaminates while cycling reducing performance in energy storage devices.M.S., Chemical Engineering -- Drexel University, 201

Laterite as a base and subbase material for flexible pavement – a review

Rapid economic growth is leading to ubiquitous expansion in highway projects around the world. Utilization of natural aggregate resources for the construction of flexible pavement has led to uncontrollable quarrying in the state of Kerala. The recent landslides in Kerala which took the lives of many people is the aftermath of extensive quarrying activities. Utilization of treated native soil in the structural layers (Subbase and base) of flexible pavement can widely avert the danger associated with ecological imbalance due to quarrying. The main objective of this review article is to enlighten the researchers and practicing engineers about the key advances developed in the last 10 years for utilizing native laterite soil in the base and subbase layers of flexible pavement. On the basis of various researches, laterite soil treated with lime, cement and other additives showed considerable enhancement in the compaction characteristics, unconfined compressive strength (UCS) and California Bearing Ratio (CBR). As stipulated by MORTH (Ministry of Road Transport and Highways), for a layer to be suitable as a subbase material in flexible pavement, minimum CBR value must be 30%. From the extensive review, it was found that the treated laterite soil satisfied the MORTH criteria for use as a subbase layer in flexible pavement. Keywords- Ferrocement, cyclic loading, flexural behavior, precast ferrocement wall, dynamic analysis, static analysi

One-dimensional disordered bosonic hubbard model: a density-matrix renormalization group study

We use the density-matrix renormalization group to study the one-dimensional bosonic Hubbard model, with and without disorder. We obtain the gaps in all phases, certain correlation functions, and the superfluid density. A finite-size-scaling analysis enables us to obtain an accurate phase diagram and the β function at the superfluid-Mott insulator transition and the Kosterlitz-Thouless essential singularity in the pure case. We also obtain coupling constants used in effective field theories for this system

Total phenolic and flavonoid content, antioxidant effects and antidiarrheal activity of balacaturbhadrika churna – an Ayurvedic preparation

485-492Balacaturbhadrika churna (BC) is an important pediatric preparation in Ayurveda. It is used to treat various diseases of gastro-intestinal tract particularly diarrhea in children. Free radicals cause oxidative damage in the intestine and are correlated with its diseases. In the current study, total phenolic and flavonoid contents of BC extracts were determined and their antioxidant evaluation in various in vitro models was carried out. Procedures mentioned in The Ayurvedic Formulary of India were followed to prepare in-house BC; alcoholic (BCAL) and aqueous (BCAQ) extracts were prepared and tested by standard procedures. BCAL was tested for antidiarrheal activity in castor oil induced model. The ethanolic extract showed better antioxidant activity in many of the models as compared to aqueous extract. The present study showed substantial amounts of flavonoids and phenolics in churna extracts. BCAL showed significant antidiarrheal activity against the tested model. The potential antioxidant and antidiarrheal activities displayed by Balacaturbhadrika churna extracts could be attributed to these contents