Entropy Definition and 999 Threads

Sen 2013 says, How serious a problem is this for LQG? Does this mean that LQG doesn't have GR as its semiclassical limit? Does that mean it's a dead theory, or maybe just that it needs to be modified? Is the technique using Euclidean gravity reliable? Since I'm not a specialist, I'd be...

Can someone explain to me why Cpln(T2/T1) = 0? Thank you.

In 250gr water at 23 oC(degrees celsius) we throw in 27gr ice at 0 oC. Find the change in entropy. (sorry if that was a bad translation but English is not my native language) The answer is 0.78 calories/oC. But I'm not sure how do this. The formula I have for entropy is: S=δQ/T I find the...

First off, just clarify that I have a very, very superficial knowledge of Physics, so my apologies if my question is based on an obvious misunderstanding of the basic principles underlying the second law of thermodynamics or if it has a rather simple answer. The doubt that I have is related...

How specifically does LQG explain how the universe can oscillate from big bang to big crunch ad infinitum? Wouldn't the total energy able to be used as work decrease after a couple of bounces? Am I simply misunderstanding or making a false assumption about what LQG's premises are? I've not...

Homework Statement Calculate entropy for density matrix with eigenvalues ##0## and ##1##. Homework Equations ##S=-\lambda_1 \ln \lambda_1-\lambda_2 \ln \lambda_2## where ##\lambda_1## and ##\lambda_2## are eigenvalues of density matrix. The Attempt at a Solution How to calculate...

Consider proton and electron are separated in space at some finite distance.Now suppose they released then the decrease in potential energy equals kinetic energy but as electrons or protons are accelerated they emit em and lose some gained kinetic energy.Also the mass is another form of...

I don't understand this: According to what modern physicists believe to be true, there is entropy that slowly converts all energy of the universe into heat that cannot do any work. Than this heat is radiated as infrared light into space. Correct? Besides infrared heat radiation, start also...

Homework Statement The resultant of a experimental run of a force (N) vs temperature (K) gives me a slope of 0.0039x - 1.0929. The slope has a (∂f/∂T)l = (∂S/∂l)T Homework Equations Equation (11) attached as PNG file We can obtain all the quantities of the right side of Eq. (11)...

¿ How meaurements increase entropy? The decoherence before the measurement increase entropy but collapse returns the state of the system to a pure state. ¿Why then measurements increase entropy

Homework Statement 100g of lead, specific heat .0345 cal/g/C at 100 C is mixed with 200 g of water at 20 C. Find the difference in entropy of system at end from value before mixing. Note: I think the book has wrong answer of 1.42 cal/K Homework Equations Before mixing entropy for water =...

ITER is the fusion reactor in southern France that hopefully will come online in 2018. According to wiki http://en.wikipedia.org/wiki/ITER The ITER fusion reactor itself has been designed to produce 500 megawatts of output power for 50 megawatts of input power. Does this mean that if...

Which has the least entropy? A 1kg diamond vs 1kg living organism I've gather that living things are generally at a state of low entropy compared to the same matter in other configurations- as though complexity goes hand in hand with low entropy. Yet a perfect chrystal is supposedly low...

Homework Statement Two 100g Aluminum cubes with T1 = 80° C and T2 = 20°C Specific heat of Al is .22 cal/g/°C. The cubes are placed in contact and in short period of time a quantity of heat, dQ , is transferred from T1 cube to T2 cube. The cubes temperatures now are 75°C and 25°C. After a...

Homework Statement For public health reasons, you are investigating small systems that turn sea water into drinking water. One portable system takes a volume of saltwater and produces two thirds that volume of freshwater with an increased concentration of salt in the other third of the volume...

I understand the Gibbs Free Energy equation that was drilled into us in Chemistry class but not even my teacher could explain what entropy had to do with free energy, and furthermore, why entropy is a driving force for a reaction. From what I understand, entropy is the distribution of energy...

move A-->B ...What about entropy change? Hi, I have a physical question regarding entropy, temperature, internal energy and mechanical energy. The situation is following: Two objects are located inside a one dimensional frictionless and adiabatic space where object “a” is an observer that...

How can a black hole have a high entropy state if the matter inside it is in a supercondensed form with maximum density,which means less degrees of freedom therefore less entropy than normal matter.Like in neutron stars we have low entropy with the neutron degenerate matter and yet a black hole...

I have a quick question. Consider the process S2 to S1 in the figure below Since this represents wet (isentropic) compression, mathematically we have ΔS=0 (assuming adiabatic compression). But if we consider the process in a physical way, we are going from a region of less disorder...

Shannon entropy of "QXZ" Hello everyone. I am trying to determine the Shannon entropy of the string of letters QXZ, taking into consideration those letters' frequency in English. I am using the formula: [SIZE="4"]H(P) = –Ʃ pilog2pi What's puzzling me is that I am expecting to calculate a...

From what I can gather, the laws of physics are time sysmmetrical- the exception being the second law of thermodynamics. So could it be that our whole experience of time is driven souly by increasing entropy? Assuming that we live in a deterministic universe(controversial I know) all past...

In my TD classes I have to deal with entropy. But what does it really mean? I know that it is the degree of disorder and the equation S=q/t. But what is this disorder? How can a physical system be aware of order and disorder since it is an abstract concept?They say that solids have high order...

I was thinking maybe the universe isn't in the chaotic state its meant be in. Rather a more organised state and the universe is still in it's younger years. This is just a thought any insight would be great.

Homework Statement At constant atmospheric pressure, 20g of water at 30C is converted into steam at 250C. Assume the heat capacity of liquid water is constant at 4.2 J/gK and the heat of vaporization at 100C is 2260 J/g. The molar heat capacity of water vapor at constant pressure is given by...

Homework Statement Hi everyone In an isochoric process ( a solid heat body with T1 temp. connected with heat bath with T2 temp) we could calculate its entropy change(heat body) from dS = Cv/T dT and entropy change of heat bath from dS = dQ / T2, using dQ = Cv dT in 1st equation ( i...

Homework Statement A monatomic ideal gas is compressed adiabatically. What is ΔS of the gas? n = 1.00 vi = 10.00 L vf = 4.00 L Constant External Pressure = 50.00 atm Homework Equations ΔU = q + w = 0 + (-PextΔV) ΔS = ∫[(qrev)/T]dQ The Attempt at a Solution In order to...

In the paper "A Mathematical theory of Communication" by Shannon I couldn't understand a theorem (Theorem 4) under the topic "The Entropy of Information Source"- Here 'H' is the entropy. Can you explain me how we get this theorem? What is this n(q)? I couldn't understand the sentence...

Hey guys, i am reading something about entropy. :confused: And got a question. The Boltzmann entropy is defined by: S=k\cdot \ln{W} W is the number of microstates connected to an given macrostate. The entropy of the microcanonical ensemble(fixed given Energy) is defined by...

For the following question, the solution manual sets du/dt (change of internal energy) = 0. Moreover, it also set the change of total entropy to zero. Why is that? An electric motor under steady load draws 9.7 amperes at 110 volts; it delivers 0.93 kW of mechanical energy. The temperature of...

It's interesting that the entropy of the gravitational field (i.e. the entropy of geometry) has never been satisfactorily defined. Since geometry is such an important part of the picture near the start of expansion, this means that total entropy around then has been undefinable, leaving...

hello, i have been given two formulae for the entropy of an ideal gas undergoing a reversible process. the correct expression is: S = Nk(s0-ln({\frac{N_0}{N}})^{5/2} + ln({\frac{T}{T_0}})^{3/2} + ln({\frac{V}{V_0}})) where s_0 is a constant, N the number of particles, T the...

I learned ΔSuniv = ΔSsys + ΔSneib If ΔSuniv > 0 the process is spontaneous. But ΔS = Q/T right? Shouldn't Qsys = -Qneib? (The heat released by the system = - heat released by the neighborhood) I cannot understand why this is wrong! If it were the case, ΔSuniv would be always zero...

The photon, "time" and entropy (ignore original title, in fact id appreciate if a mod would change it. It was not my intention to have a conversation about time, lol!) Can we view a closed system of just photons, as ever, or usually, being subject to entropy (defined by the whole 2nd law...

Is there any relationship between phase space and entropy? regarding to decay of particles

Homework Statement In the entropy equation 1S2 + ∫δQ/T = S2 - S1, what is the difference between 1S2 and ∫δQ/T? So for example if we have two reservoirs, one hot and one cold and heat is transferred in between we have: Shot = Q/Thot Scold = Q/Tcold Where do the Shot and Scold terms...

Fluctuation theorem says that there will be fluctuations in microscopic scale that results local decreases in entropy even in isolated systems. According to the Poincaré recurrence theorem, after sufficiently long time, any finite system can turn into a state which is very close to its initial...

Homework Statement Expression for the entropy and internal energy of black body radiation. Using the below relations: Homework Equations Total free energy for black body: $$ F = (k_b TV/\pi^2) \int k^2 ln[1-exp(-\hbar ck/k_b T)]dk $$ Relationship between partition function and internal...

we know the entropy in each process increases is it true for absolute negative temperature?

How could the entropy of a continuous system, like the electromagnetic field, be defined? Obviously you can't use something like the log of the phase space volume, but I can't think of anything that would work.

Hi,I m just beginner in physics,but actually I don need exact expression of physical laws in math language.I know,math is language of physics but still... So,I m looking for answer to my questions about origin of Clausius s entropy. I this article: http://www.panspermia.org/seconlaw.htm is...

Homework Statement http://postimage.org/image/9artvc1h5/ see attached Homework Equations ΔS=Q/T The Attempt at a Solution The real issue I'm having is how to go about solving this, I think I'm going to need to use kinematics to find the time the gold is exposed to the air...

I am reading Cycles of Time by Penrose, page 71-72. Could someone explain if the universe started out with at a state of extraordinarily tiny entropy or a state of maximum entropy and what proof or theories do we have to justify this choice. I find the explanation in the book confusing...

What are the formulas for entropy and internal energy in Fermi-Dirac statistics, and how do I derive them?

Homework Statement In a previous problem I had to find the entropy of a black hole where I ended with this: S_{BH}=\frac{8 \pi^2 G M^2 k}{h c} Now I am to find the temp, given the energy of a black hole is mc2. Homework Equations T=(\frac{\partial S}{\partial u})^{-1} The...

Homework Statement The entropy of an ideal paramagnet is given by S=S_{0}+CE^{2}, where E is the energy (which can be positive or negative) and C is a positive constant. Determine the equation for E as a function of T and sketch your result. Homework Equations [tex] \frac{1}{T}=\frac{\delta...

I don't want to argue about whether the notion of "wave function collapse" is a good way of understanding quantum mechanics, or not. For the purposes of this discussion, let's just adopt uncritically the naive approach to quantum mechanics, that: Between measurements, the system evolves...

A formula for entropy: dS=dQ/dT This is a formula that represents the rate of change of heat with respect to temperature. Q=mcdT This is another formula that states how the temperature changes as heat is added. from this can we say that entropy is just specific heat capacity * Mass...

So, until now I know: (DV/DS)p=(DT/Dp)s=a*T/cp*(rho) (enthalpy) (Dp/DT)v=(DS/DV)t=-a/k (helmoltz) (DS/Dp)t=-(DV/DT)p=-Va (gibbs) a=expansion coefficient k=isothermal compression coefficent cp=heat capacity at constante pressure I want to deduce DT/DV at constant entropy=(DT/DV)s. BUT...

I'm having a hard time reconciling two ideas in physics. One is that systems tend towards the maximum amount of disorder, or "entropy always increases". And, when two systems are brought together they are likely to be found at the energy E* which maximizes the number of states of the...

Hello I may well be all wrong about this but I am trying to understand from a microscopic point of view why Entropy is a concave function of internal energy. I found this in the following .pdf: http://physics.technion.ac.il/ckfinder/userfiles/files/avron/thermodynamics_potentials.pdf I...