Engineering synthetic materials that mimic the remarkable complexity of living organisms is a fundamental challenge in science and technology. We study spatiotemporal patterns emerge when an active nematicfilm microtubules molecular motors encapsulated within shape-changing lipid vesicle. Unlike equilibrium systems, where defects are largely static structures, nematics move spontaneously can be described as self-propelled particles. The combination activity, topological constraints vesicle...

We describe experimental investigations of the structure two-dimensional spherical crystals. The crystals, formed by beads self-assembled on water droplets in oil, serve as model systems for exploring very general theories about minimum-energy configurations particles with arbitrary repulsive interactions curved surfaces. Above a critical system size we find that crystals develop distinctive high-angle grain boundaries, or scars, not found planar number excess defects scar is shown to grow...

A detailed analysis is given of chiral-symmetry breaking in the large-flavor (N) limit quantum electrodynamics (2+1) dimensions. Analytical and numerical solutions homogeneous Dyson-Schwinger equation for fermion self-energy combined with a computation effective potential bilinear show that it energetically preferable theory to dynamically generate mass fermions. The magnitude roughly exponentially suppressed N from fundamental dimensionful scale \ensuremath{\alpha}\ensuremath{\equiv}N...

Many systems in nature and the synthetic world involve ordered arrangements of units on two-dimensional surfaces. We review here fundamental role payed by both topology underlying surface its detailed curvature. Topology dictates certain broad features defect structure ground state but curvature-driven energetics controls structured phases. Among surprises are appearance structures that would normally be thermal excitations thus prohibited at zero temperature. Examples include excess...

Liquid crystals inevitably possess topological defect excitations generated through boundary conditions, applied fields, or in quenches to the ordered phase. In equilibrium, pairs of defects coarsen and annihilate as uniform ground state is approached. Here we show that active liquid exhibit profoundly different behavior, depending on degree activity its contractile extensile character. While systems enhance annihilation dynamics passive systems, act drive apart so they swarm around manner...

The name active matter refers to any collection of entities that individually use free energy generate their own motion and forces. Through interactions, particles spontaneously organize in emergent large-scale structures with a rich range materials properties. active-matter paradigm is applied living nonliving systems over vast dynamic range, from the organization subnuclear cell collective at human scale. diverse phenomena exhibited by these all stem defining property as an assembly...

The production of strings (disclination lines and loops) has been observed by means the Kibble mechanism domain (bubble) formation in isotropic-nematic phase transition uniaxial nematic liquid crystal 4-cyano-4'-n-pentylbiphenyl. number formed per bubble is about 0.6. This value reasonable agreement with a numerical simulation experiment which used for order parameter space crystal.

We propose and analyze an effective free energy describing the physics of disclination defects in particle arrays constrained to move on arbitrary two-dimensional surface. At finite temperature interacting disclinations is mapped a Laplacian Sine-Gordon Hamiltonian suitable for numerical simulations. then specialize case spherical crystal at zero temperature. The ground state analyzed as function ratio defect core Young's modulus. argue that contribution becomes less important limit R >> a,...

We attack the generalized Thomson problem, i.e., determining ground state energy and configuration of many particles interacting via an arbitrary repulsive pairwise potential on a sphere continuum mapping onto universal long range interaction between angular disclination defects parametrized by elastic (Young) modulus Y underlying lattice core E(core) isolated disclination. Predictions from theory for agree with numerical simulations power law interactions form 1/r(gamma) (0<gamma<2) to four...

The behavior of ten-dimensional superstrings at high temperatures is studied by use the microcanonical ensemble. We focus on closed superstring theories. massive string excitations alone have negative specific heat. Such a system can reach equilibrium with zero modes if energy carried less than given fraction total energy. temperature then exceed Hagedorn temperature. Some consequences for evolution universe are discussed.

Topological defects are distinctive signatures of liquid crystals. They profoundly affect the viscoelastic behaviour fluid by constraining orientational structure in a way that inevitably requires global changes not achievable with any set local deformations. In active nematic crystals, topological only dictate director, but also act as sources motion, behaving self-propelled particles. this article, we present detailed analytical and numerical study mechanics

We study the organization of topological defects in a system nematogens confined to two-dimensional sphere (S2). first perform Monte Carlo simulations fluid hard rods (spherocylinders) living tangent plane S2. The is adiabatically compressed until we reach jammed nematic state with maximum packing density. exhibits four +1/2 disclinations arrayed on great circle. This arises from high elastic anisotropy which splay (K1) far softer than bending (K3). also introduce and lattice model S2...

We formulate the statistical dynamics of topological defects in active nematic phase, formed two dimensions by a collection self-driven particles on substrate. An important consequence nonequilibrium drive is spontaneous motility strength $+1/2$ disclinations. Starting from hydrodynamic equations nematics, we derive an interacting particle description that includes torques. show activity, within perturbation theory, lowers defect-unbinding transition temperature, determining critical line...

Topological defects play a central role in the physics of many materials, including magnets, superconductors, and liquid crystals. In active fluids, become autonomous particles that spontaneously propel from internal stresses drive chaotic flows stirring fluid. The intimate connection between defect textures flow suggests properties materials can be engineered by controlling defects, but design principles for their spatiotemporal control remain elusive. Here, we propose symmetry-based...

The 4-dimensional theory of a 1-form Abelian gauge field A coupled to 2-form (antisymmetric tensor) potential B is studied. two invariances the admit coupling mB ∧ F where strength (F=dA) A. It shown that this unitary, renormalizable massive spin-one with no additional degrees freedom. In sense, it generalization four dimensions topological mechanisms in (the Schwinger model) and three (Chern-Simons theory). issue spontaneous symmetry breaking also examined.

It is shown that a black hole of fixed mass can carry arbitrary axionic charge. The unique static black-hole solution found to have vanishing axion field strength but nonvanishing potential. charge cannot be detected by point particles, strings in process analogous the Aharonov-Bohm effect. argued existence may play significant role late stages evaporation.

We argue that the Kaaumlhler geometry of loops on space-time describes bosonic string theory. The potential is dynamical (field) variable closed-bosonic-string equation motion for this field a generalized Ricci tensor vanishes. Loops flat space constitute solution only in 26 dimensions.

The spontaneous generation of parity- ($P$) and time-reversal- ($T$) violating masses in (2+1)-dimensional QED is studied the large-$N$ limit, where $N$ number two-component complex fermions. Energy considerations various symmetry-breaking patterns indicate that $P$ $T$ are not spontaneously broken, even though which individually violate these symmetries dynamically generated.