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Questions tagged [soft-matter]

Soft-matter is a vast field of research at the interfaces between physics, chemistry and biology. It consists in the study of the physical properties of composite objects described by a characteristic energy scale of the excitations of a few room temperature thermal energy.

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Resources on Phase Ordering Dynamics and Non-Linear System

I am doing a course on Non-Equilibrium Physics. Prof. was initially following Strogatz but has now started teaching Phase ordering dynamics, Cahn-Hillard equation and all? I can't seem to find a good ...
6 votes
1 answer
176 views

Why do stones in a garden rise to the surface?

Why do stones in a garden rise to the surface? I haven't done my own research on the subject, but experienced gardeners seem to suggest that, even if the garden is cleaned from stones, they reappear ...
Roger V.'s user avatar
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1 answer
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Time derivative term in Navier Stokes equation for fluid in porous media

I was reading the research paper Homogenization of peristaltic flows in piezoelectric porous media and came across the hydrodynamic equation: $$\mu \nabla^2 v^f -\underline{ \rho_f (\dot{v}^f + w \...
user134613's user avatar
1 vote
0 answers
270 views

I want to know: what is the principle that causes this phenomenon? [closed]

The effect of fractal fingering can be observed if a droplet of an ink-alcohol mixture is deposited onto diluted acrylic paint. How are the geometry and dynamics of the fingers influenced by relevant ...
aoxue's user avatar
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1 vote
0 answers
110 views

Non-linear corrections to the Oseen-Frank free energy density

A nematic liquid crystal is essentially a fluid of long, rod-like molecules whose average orientation is dictated by a vector field $\mathbf {\hat {n}} $. The so-called Frank-Oseen (free) energy (...
Daniel Castro's user avatar
1 vote
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37 views

How can we calculate deposition flux in terms of monolayer per second?

In the nucleation and growth theory, I read the unit of deposition flux of atoms in a substrate in terms of monolayer per second. But could not figure it out how to calculate the flux in terms of ...
no one's user avatar
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4 votes
0 answers
72 views

Question about 1D Percolation Theory [closed]

I am currently reading "Introduction to Percolation Theory" by Stauffer and Aharony and am doing the problems. Question 2.2 wants me to calculate a closed-form expression for the $k$-th ...
Brasswyrm's user avatar
0 votes
1 answer
81 views

Homotopy group for spin-1 BEC

Homotopy group can be used to classify topological defects. The procedure is Find the Lie group $G$ that leaves the free-energy functional invariant when transforming $\psi$, where $\psi$ is the ...
Hao's user avatar
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1 answer
366 views

How to specify the dimension of the simulation box to run molecular dynamics simulation?

I want to study the physical properties of binary liquids, molecular dynamics simulation using gromacs software is used to simulate the liquids. To set the initial coordinate configuration, how do we ...
Abdul Kareem U's user avatar
0 votes
1 answer
73 views

Converting order parameter to director (nematics)

If I have a differential equation for the order parameter of a uniaxial nematic, like $\frac{\partial S_{\alpha \beta}}{\partial t} = f(S_{\alpha \beta})$, for $S_{\alpha \beta} = S(n_{\alpha}n_{\beta}...
user12614190's user avatar
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1 answer
566 views

Scaling of the shear rate with pipe diameter

In a laminar flow regime the flow profile in a pipe should be given by: $$ v(r) = \frac{\Delta p}{4 \eta l} (R^2-r^2)$$ If we assume that the radial shear rate is a meaningful indicator for the ...
amh23's user avatar
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1 vote
2 answers
151 views

What determines water flow speed in the Clever Dripper coffee maker?

Recently James Hoffmann (a YouTuber that has a coffee channel) posted a video on 'the ultimate technique of using the Clever Dripper'. Many users of this brewer have experienced 'choking' of the brew, ...
RFermin's user avatar
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3 votes
1 answer
153 views

Why is the energy required to bend a flat bilayer membrane to vesicle independent of its radius?

Imagine that we have a flat bilayer sheet (let it be a disc-shaped bilayer) lipid membrane. When I naively think about this system being bent to form a vesicle (closed bilayer membrane), my intuition ...
dexterdev's user avatar
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1 vote
1 answer
144 views

Using Persistence length to establish straightness of position data

In the following picture I am showing 3D position data for 4 different tracks just to illustrate how the tracks looks like. As we can see that we have all kind of behaviors occurring from helical ...
Junaid Mehmood's user avatar
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1 answer
44 views

Force balance that includes solution gradient

In the provided figure, pistons seal the top and bottom of a cylinder of cross sectional area $A$ containing solution, which is split into two chambers via a semi-permeable barrier. The initial number ...
user12614190's user avatar
-2 votes
2 answers
268 views

Does magnetic field exist throughout space?

My question is quite subjective and I could not find a suitable explanation to whether there is a magnetic field in space beyond earth .I read one of the article stating Interstellar dust clouds have ...
imposter's user avatar
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1 vote
0 answers
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Are PMLs also used for soft-matter structural dynamics modelling as they are commonly used in Wave Propagation modelling?

Numerical modelling of waves by FDTD method makes use of PMLs to establish absorbing boundaries. I recently began modelling soft-material structural dynamics (for biological cells) using FEM where the ...
Danish Shamoon's user avatar
1 vote
4 answers
533 views

What makes materials soft/bendy? What is the specific name for this property?

What is the name of the property that materials like cloth have that allows it to be bent or folded on itself without any significant elasticity, but also not permanently deformed either? Softness? ...
Curtwige's user avatar
1 vote
0 answers
94 views

Bifurcations in Statistical Physics

I am currently a grad level student in physics with much interest in statistical and soft-matter physics (equilibrium and out of equilibrium); I am currently taking a course in numerical methods for ...
Laudicina Corentin's user avatar
1 vote
0 answers
75 views

Can an electrorheological non-Newtonian fluid be in a definite shape for a short time?

I have seen this Experiment: ELECTRORHEOLOGICAL FLUIDS and balloon Experiment (Stops flow with Static Electricity), and have seen that simple cornstarch is affected by electrostatic forces. The ...
kryomaxim's user avatar
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1 vote
1 answer
267 views

Spatial Correlation Function and Ensemble average

Well, I was reading the Statistical Mechanics book by Pathria, to understand the concepts of the correlation function. I want to quote some lines. Spatial correlation functions are based on n-...
Ritwick Sarkar's user avatar
1 vote
1 answer
84 views

Text Recommendation: Random Walks (for physicists)

I am an incoming graduate student in Theoretical Physics in the Netherlands, and I would like to know if any of you could recommend texts on random walks with applications to physics. My university ...
1 vote
1 answer
45 views

Intrpretting questions on Fickian diffusion

I am considering the Zimm model for polymer dynamics, and have come across a question Find an expression for the time it takes for the polymer to diffuse a distance equal to its contour length $L=...
Meep's user avatar
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2 votes
1 answer
171 views

Soft condensed matter: the partition function for cluster formation

I am stuck on understanding the form of the partition function presented in my lectures, for self assembly of clusters from monomeric molecules. If there are $N_T$ molecules that can form clusters of ...
Meep's user avatar
  • 3,987
0 votes
1 answer
291 views

Overdamped Approximation

I am reading the paper Information transfer and behavioural inertia in starling flocks (Attanasi et al, 2014) in the field of active matter for an undergraduate course I am taking. The paper describes ...
Avishai Barnoy's user avatar
1 vote
1 answer
1k views

Derivation of the upper convected time derivative

I read on wikipedia theat the upper convected time derivatvie is the rate of change of some tensor property of a small parcelof fluid that is written in the coordinate system rotating and stretching ...
J.A's user avatar
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1 answer
74 views

Interface between two phases minima of the energy and interface between a minimum and a "vacuum"

Cahn and Hilliard define the energy of an interface: the difference per unit area of interface between the actual free energy of the system and that which it would have if the properties of ...
J.A's user avatar
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0 votes
0 answers
25 views

Does crosslinking a polymer film increase the stress within the film?

If I crosslink a polymer film, does that increase the internal stress of the film? Intuitively I think it should for entropy reasons; chains with greater links are more restricted and have a smaller ...
user668074's user avatar
1 vote
1 answer
879 views

Helfrich energy derivation

The Helfrich elastic energy of membranes is given by $F = \int dS (\kappa H^2 + \kappa_G K)$ where $H$ is the mean curvature and $\kappa_G$ is the Gaussian curvature. The derivation in the original ...
Botond's user avatar
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2 votes
2 answers
768 views

Calculating Elastic Potential Energy of a Stretched Sheet

Essentially, I'm trying to determine the amount of elastic potential energy stored in a thin, elastic sheet that has gone under some type of stretching (ex. A flag of stretchy fabric waving in the ...
AlexP's user avatar
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1 vote
1 answer
104 views

Shear strain correlations from displacement Fourier transform

Currently working with molecular dynamics simulations, I would like to compute shear strain correlations in my 2-dimensional system. How I used to do things Accumulated shear strain at position $\...
yketa's user avatar
  • 102
1 vote
0 answers
116 views

Splitting the mean in the (Backward) Fokker-Planck

A method for deriving the Fokker-Planck equation is outlined below$^1$ (I believe it is a simplified version of the Kramers-Moyal expansion). Set: $$P(\vec x, t+\Delta t) =\left<\delta(\vec ...
Quantum spaghettification's user avatar
1 vote
0 answers
44 views

Is there any method to calculate surface tension of packing of particles under external potential

I want to calculate surface tension of stacking of particle which the surface is under a repulsive potential. The repulsive potential applying the force to the particles to have a surface (or ...
Ji woong Yu's user avatar
0 votes
1 answer
43 views

Partition function for a bidisperse packing of soft-core particles

My goal is to study the nematic order in bidisperse packings of soft-core spheroidal particles of identical aspect ratio with harmonic repulsion from a statistical mechanics point of view by adapting ...
yketa's user avatar
  • 102
0 votes
2 answers
322 views

Thermostat code for molecular dynamics with angle dependent potential

I'm building molecular dynamics code for the specific purpose of simulating Janus particle because no package supports the custom angle dependent potential to my knowledge. I'm building thermostat ...
Ji woong Yu's user avatar
0 votes
1 answer
63 views

Steps in minimising free-Interfacial thickness

I am trying to obtain the interfacial thickness of a mixture of two fluids in the context of the Cahn-Hilliard equation. In the simplest case and in one dimension the free energy has the form $$F=\...
Javier's user avatar
  • 1
4 votes
2 answers
371 views

Why is it harder to situp on solid floor?

When I situp on solid floor it is harder for me to lift my body upwards versus on a soft/foamy floor which I can do a lot.
Rod_Algonquin's user avatar
3 votes
1 answer
249 views

Ewald summation without repeating one particle periodically?

I need to perform an Ewald summation for a Brownian Dynamics simulation. In the normal Ewald summation procedure, all particles in the simulation box are periodically repeated in the neighbouring ...
user3107708's user avatar
2 votes
1 answer
104 views

Deformation in the nematic phase of a liquid crystal survived in solid state

Does anyone know if I cool a liquid crystal with a deformed nematic phase quickly it will preserve the deformation in the crystal lattice? I didn't never see that in classical books on liquid crystals....
Caetes's user avatar
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-1 votes
1 answer
168 views

Estimate the persistence length of a rubber band [closed]

Not much more to say here, it's all in the question. The best, most convincing estimate will be chosen as the correct answer. EDIT: Assume the rubber band is at room temperature, with thickness $t$ ...
Izzhov's user avatar
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1 vote
0 answers
50 views

Will the usage of Exo-Skeleton Gear actually weaken the human body over time? [closed]

As we all know, Exo Skeletons as they exist now are just a series of Force multiplying apparatuses working together, also the human body changes to accommodate environment specific factors in order to ...
Clement Mark-Aaba's user avatar
7 votes
1 answer
3k views

Equivalent tensor order parameters of nematic liquid crystals?

I found in the literatures two different definitions of the tensor order parameter of nematic liquid crystals. One is $$ Q_{ij}=\frac{S}{2}(3n_{i}n_{j}-\delta_{ij}), $$ where $S$ is the scalar order ...
user avatar
4 votes
1 answer
228 views

Is the $2\pi$ disclination topologically stable for a 2d nematic liquid crystal?

For a three dimensional liquid crystal, a $2\pi$ or charge $1$ disclination is topologically unstable. The is generally explained as the disclination can lose its core singularity by "escaping from ...
user avatar
0 votes
1 answer
534 views

Why is mud muddy?

How to explain properties of mixture of sand with water? Why is it so coherent and slippery at the same time? Is it due to hydrogen bonds? Why is mud of smaller grains more slippery and incoherent ...
user46147's user avatar
  • 3,034
8 votes
3 answers
2k views

Are there materials that get softer with temperature decrease?

Could be there material that begins melting/softening when it's temperature is lowered? I would say no, but I've seen enough physics to know that not always life is so easy. Moreover I think I've ...
user46147's user avatar
  • 3,034
3 votes
1 answer
2k views

Why does dust stick so well to fan blades? [duplicate]

After reading and understanding the reasons why dust stick to rotating fan propeller, I am interested to find out why the dust particles stick so well. Spraying powerful jets of water does not ...
Question Overflow's user avatar
1 vote
1 answer
137 views

What happens when a bacteria tumble? Is it an active or a passive process? [closed]

I was wondering what actually happens during the tumbling process of a "run and tumble" process. When the bacteria stops to tumble and reorient itself, is that an active process, or is the ...
user30584's user avatar
11 votes
4 answers
18k views

What is the physics behind a soap bubble?

A soap bubble is an extremely thin film of soapy water enclosing air that forms a hollow sphere with an iridescent surface. What fluid dynamical process occurs during the popping of a soap bubble?
dan's user avatar
  • 111
16 votes
4 answers
2k views

Where can I find the full derivation of Helfrich's shape equation for closed membranes?

I have approximately 10 papers that claim that, from the equation for shape energy: $$ F = \frac{1}{2}k_c \int (c_1+c_2-c_0)^2 dA + \Delta p \int dV + \lambda \int dA$$ one can use "methods of ...
Samuel Reid's user avatar
1 vote
1 answer
644 views

Resource for intermolecular forces in soft condensed matter

I need a book dealing in particular with the intermolecular forces and, if possible, the diffusive processes. Someone knows an appropriate one?