See more at https://posfisica.ufv.br/en/research/ 

Complex Systems

Dynamic processes in complex networks

Studies of dynamic processes in complex networks are proposed and analyzed by analytical and computational methods. The dynamics of epidemic propagation is investigated in random (free of scale, small world, etc.) and real networks, including analysis of the spread of vector-borne diseases and in metapopulations. Models for forming opinions, spreading rumors and critical phenomena, in general, are also objects of study in complex networks.

Micro-rheology of viscoelastic materials

From theoretical-computational approaches based on micro-rheology, we seek to elucidate the relationship between the macroscopic mechanical response of viscoelastic materials (eg, hydrogels and collagen) from microscopic interactions between their fundamental constituents, for example, flexible filaments (eg, polyelectrolytes ) and semi-flexible filaments (eg, fibrils, actin, virus, DNA, fribrin, etc.). The main idea is to develop theoretical models based on the results obtained from multi-scale computer simulations that use Brownian dynamics methods.

Nucleation in disordered systems

Theoretical and computational studies on the phenomena of nucleation and particle aggregation in biomolecular and quasicrystalline systems. Computer simulation developments include simulation methods for out-of-balance systems such as kinetic Monte Carlo. In addition, we evaluate alternative theoretical approaches to the Classic Theory of Nucleation, since it cannot be applied to the studied systems.

Phase transitions in frustrated magnetic systems

Development of computer simulations based on advanced Monte Carlo algorithms to study the thermostat of low-dimensional magnetic materials that have frustrated interactions. The main interest in this line of research is to elucidate the nature of the phase transitions present in these systems.

Interface aggregation and growth phenomena

Simulations, experiments and scale analyzes of the dynamics of kinetic aggregation processes are carried out here, with emphasis on the growth of self-organized nanostructures, epitaxial films, electrodeposition and propagation in porous media. In addition, a theoretical study is made of the mapping of equilibrium and far-equilibrium models in self-related interfaces.

Theoretical and Experimental Biological Physics

Population dynamics

Mathematical models for agricultural pests are constructed and analyzed by analytical methods (dynamic systems theory) and computational methods (simulation of cellular automata and numerical integration of EDOs / EDPs). Processes of biological invasion mediated by allelopathy, insect dispersion guided by pheromones and trophic web dynamics are examples studied based on models of multiple scales

Mathematical oncology

In this study we propose mathematical models of multiple scales for the growth of tumors and the effect of anti-cancer therapies. In them, the microscopic (molecular) and mesoscopic (cellular) scales are described by stochastic cellular automata with transition probabilities determined by local concentrations of continuous fields (nutrients and growth factors – macroscopic scale). The results can be compared with histopathological patterns, spheroids and tumors induced in animals.

Magnetic Systems and Nanostructured Magnetic Materials

Topological excitations in materials

“This is not a utopia (not place), but a topia”. In the physics of modern condensed matter, there are some very stable types of excitations (objects that often resemble particles) that arise in several phenomena: topological pseudo-particles. We must emphasize the word topology, a branch of mathematics that extravagantly says that the donut would be like the cup. Topology is very common in current physics (tops comes from Greek and means place). These topological objects reside in several different systems (magnetic, liquid crystals, superconductors, etc.) mainly in low dimensions (one-dimensional and two-dimensional materials) and, due to their topological nature, are as difficult to be undone as a blind knot. The mathematical theorem of the hairy sphere is a good example to see how these topological elements can form. This stability is usually associated with a topological load. It is this aspect that makes them of great interest in the most recent research areas. Some of these structures are known as vortices, solitons, skyrmions, and have a topological load given by an integer; we can also mention the controversial Merons, which have a semi-entire topological charge.

Topological States of Matter

Topological States of Matter are states characterized by topological properties that emerge from the system’s microscopic degrees of freedom. Examples of such states are the Whole and Fractional Quantized Hall Effect, the two-dimensional and three-dimensional Topological Insulators, topological superconductors, among countless others. This line of research involves the study of exotic properties of these materials, such as the emergence of Majorana fermions, which have an enormous potential for application in quantum computing, the presence of anyons, response functions that carry topological characteristics of the system, among others.

Magnetism and Nanomagnetism

“Spin is the main protagonist here”. We studied magnetic systems in low dimensions and their dynamic and thermodynamic properties, emphasizing questions about phase transition and correlation functions. Among the materials investigated by us are zero-dimension (“pontolândia”), dimension-1 (“linhalândia”), systems between 1 and 2 dimensions (“escadolândia”) and dimension-2 systems (“planolândia”) , besides, of course, the “spheroland” (three-dimensional systems). On the other hand, magnetic systems of very small sizes are also of fundamental importance for the development of new technologies. On a nanometric scale (1 centimeter divided by 10 million), many structures in condensed matter exhibit topological pseudo-particles. The nanometric magnetic structures have very interesting shapes such as disks, cylinders, racetracks, etc. Our goal is to study how these things (topology and materials of different shapes on the scale of the very small) fit together and how we could use such fittings for new technological structures. It is very common to see carousel-like movements of vortexes on magnetic nanodisks as well as skyrmion racing on magnetic nano-tracks. Controlling the movements of topological objects and even electrons in nanomagnetic systems is of fundamental importance for new technologies such as skyrmonic, spintronic, magnetronic and some other “tronics”.

Frustrated magnetic systems frustrados

“Frustration generates exciting physics”. In this line of research, we investigated mainly spin liquids and spin ices. Such materials exhibit extraordinary properties such as disordered ground states and fractionation. Imagine a system that never organizes, even in its fundamental state at absolute zero. This is exactly what happens with spin liquids, leading to beautiful excitations such as fragmented electrons (spinons, chargons, etc.). Examples of our recent contributions involve fractionalized pseudoparticles in artificial spin ice that are called Nambu magnetic monopoles. Such monopoles have an energetic cord that connects opposite poles.

New Materials

We are also interested and, therefore, we have investigated the properties of materials of significant importance in current physics: superconductors at high temperatures, graphene, topological insulators, etc. Some of these materials (usually two-dimensional) support massless electron-like particles and possibly Majorana fermions, which in general are only seen in condensed materials (and not in our Universe).

Investigation of devices by micromagnetic simulation

We investigate by micromagnetic simulation, using open codes or codes developed by partners, prototypes to be produced experimentally in the future. In this line, we investigate the application of magnetic objects with topological protection in future devices to be developed experimentally. These studies have provided the proposition of several new devices to be investigated for application such as magnetoresistive tape memories, logical transistors, neuromorphic systems and nano-oscillators.