ترغب بنشر مسار تعليمي؟ اضغط هنا

Generalized Deam-Edwards Approach to the Statistical Mechanics of Randomly Crosslinked Systems

131   0   0.0 ( 0 )
 نشر من قبل Xiangjun Xing
 تاريخ النشر 2013
  مجال البحث فيزياء
والبحث باللغة English
 تأليف Xiangjun Xing




اسأل ChatGPT حول البحث

We address the statistical mechanics of randomly and permanently crosslinked networks. We develop a theoretical framework (vulcanization theory) which can be used to systematically analyze the correlation between the statistical properties of random networks and their histories of formation. Generalizing the original idea of Deam and Edwards, we consider an instantaneous crosslinking process, where all crosslinkers (modeled as Gaussian springs) are introduced randomly at once in an equilibrium liquid state, referred to as the preparation state. The probability that two functional sites are crosslinked by a spring exponentially decreases with their distance squared. After formally averaging over network connectivity, we obtained an effective theory with all degrees of freedom replicated 1 + n times. Two thermodynamic ensembles, the preparation ensemble and the measurement ensemble, naturally appear in this theory. The former describes the thermodynamic fluctuations in the state of preparation, while the latter describes the thermodynamic fluctuations in the state of measurement. We classify various correlation functions and discuss their physical significances. In particular, the memory correlation functions characterize how the properties of networks depend on their history of formation, and are the hallmark properties of all randomly crosslinked materials. We clarify the essential difference between our approach and that of Deam-Edwards, discuss the saddle-point order parameters and its physical significance. Finally we also discuss the connection between saddle-point approximation of vulcanization theory, and the classical theory of rubber elasticity as well as the neo-classical theory of nematic elastomers.



قيم البحث

اقرأ أيضاً

Noethers calculus of invariant variations yields exact identities from functional symmetries. The standard application to an action integral allows to identify conservation laws. Here we rather consider generating functionals, such as the free energy and the power functional, for equilibrium and driven many-body systems. Translational and rotational symmetry operations yield mechanical laws. These global identities express vanishing of total internal and total external forces and torques. We show that functional differentiation then leads to hierarchies of local sum rules that interrelate density correlators as well as static and time direct correlation functions, including memory. For anisotropic particles, orbital and spin motion become systematically coupled. The theory allows us to shed new light on the spatio-temporal coupling of correlations in complex systems. As applications we consider active Brownian particles, where the theory clarifies the role of interfacial forces in motility-induced phase separation. For active sedimentation, the center-of-mass motion is constrained by an internal Noether sum rule.
369 - F. Becattini 2019
In this work the non-equilibrium density operator approach introduced by Zubarev more than 50 years ago to describe quantum systems at local thermodynamic equilibrium is revisited. This method - which was used to obtain the first Kubo formula of shea r viscosity, is especially suitable to describe quantum effects in fluids. This feature makes it a viable tool to describe the physics of the Quark Gluon Plasma in relativistic nuclear collisions.
188 - J. Tailleur , M. E. Cates 2008
We consider self-propelled particles undergoing run-and-tumble dynamics (as exhibited by E. coli) in one dimension. Building on previous analyses at drift-diffusion level for the one-particle density, we add both interactions and noise, enabling disc ussion of domain formation by self-trapping, and other collective phenomena. Mapping onto detailed-balance systems is possible in certain cases.
We show that near a second order phase transition in a two-component elastic medium of size L in two dimensions, where the local elastic deformation-order parameter couplings can break the inversion symmetry of the order parameter, the elastic moduli i diverges with the variance of the local displacement fluctuations scaling as $[ln(L/a_0)]^{2/3}$ and the local displacement correlation function scaling as $[ln(r/a_0)]^{2/3}$ for weak inversion-asymmetryThe elastic constants can also vanish for system size exceeding a non-universal value, making the system unstable for strong asymmetry, where a 0 is a small-scale cut-off. We show that the elastic deformation-order parameter couplings can make the phase transition first order, when the elastic modulii do not diverge, but shows a jump proportional to the jump in the order parameter, across the transition temperature. For a bulk system, the elastic stiffness does not diverge for weak asymmetry, but can vanish across a second order transition giving instability for strong asymmetry, or displays jumps across a first order transition. In-vitro experiments on binary fluids embedded in a polymerized network, magnetic colloidal crystals or magnetic crystals could test these predictions.
We study the statistical mechanics of double-stranded semi-flexible polymers using both analytical techniques and simulation. We find a transition at some finite temperature, from a type of short range order to a fundamentally different sort of short range order. In the high temperature regime, the 2-point correlation functions of the object are identical to worm-like chains, while in the low temperature regime they are different due to a twist structure. In the low temperature phase, the polymers develop a kink-rod structure which could clarify some recent puzzling experiments on actin.
التعليقات
جاري جلب التعليقات جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
mircosoft-partner

هل ترغب بارسال اشعارات عن اخر التحديثات في شمرا-اكاديميا