Evolution Definition and 735 Threads

I am an evolutionary theoretician, focusing on the dynamics of process that shape the generation of variation in organisms, including properties such as mutational robustness, the evolution of evolvability, and modularity in the genotype-phenotype map. My main mathematical area is development...

Looking for research answering the following question: "What is the earliest point in time, in the Universe, that exoplanets comprised of life-sustaining elements such as carbon, water, etc. could have formed?" I've read that the earliest known stars likely formed about 500 million years after...

Are temporary embryonic structures like gill clefts included under "Vestigeal organs"??

Hello All :) I've heard it proposed that a reason for the fine tuned nature of our universe in a way to allow the existence of complexity and life could be that the universe itself is the product of evolution in a multi-verse. I don't want to debate around the anthropological principle as I am...

Can anyone provide me with a list of simple mnemonics to learn phylogeny of horse,phylogeny of humans,geological times list and others?? Ty in advance !

I was thinking about this the other day, and I was curious about what future stars will contain for their cores. If I understand correctly, the first generation stars in the early universe didn't contain (or contained significantly less) metals. As stars evolved, they contained more metals (or...

Why aren't microspheres and protocells considered as living beings? What I know is that they do reproduce and exhibit metabolism.. so they fulfill the basic criteria of living systems. I am really confused about it!

Does DNA exist in all living things...Humans, extremophiles, plant life?

I got to wondering about the development of the human brain, and the consequent development of human intelligence (and to an extent the mind). I googled the question and after reading several articles, was left not much the wiser in regard to the development of 'intelligence'. Part of my problem...

The equivalence between descriptions of time evolution in QM are rigorously defined and proved for conservative systems as explained for instance among many other sources in Jauch's "Foundations of quantum mechanics" in the chapter 10. However, and an exception is the cited reference, it is not...

Biologists split life into two broad categories: prokaryotes and eukaryotes. Prokaryotes are relatively simple single-celled organisms and are split into two groups (bacteria and archaea). Eukaryotes, on the other hand, are much more complex cells containing specialized compartments such as...

I have thought for some time that it is physically correct to treat photon source as time evolving rather than photon state (i.e. using Heisenberg picture rather than Schrodinger picture) so I was glad to find this picture in Feynman's book (QED: The Strange Theory of Light and Matter): In...

Hello, I will need to talk to students about the evolution of a solar-like star. We will look at a diagram like the following: It will be a descriptive presentation, no mathematics. I know pretty well what happens until the formation of the carbon core. The linear upper line happens because...

Homework Statement Prove that Homework Equations [/B]The Attempt at a Solution Without cosmological constant, one finds that where w is the ratio between pressure and density.[/B]

My apologies for starting a thread on a seemingly easy and searchable topic. But, alas, I've searched here, Amazon, google, Goodreads etc and wanted to get some recommendations. Specifically book suggestions on The Sun and / or Stellar evolution. I've ran across several intriguing textbooks...

If a methane-filled planet or moon like Titan was pulled toward a star, as the methane warmed and became gaseous, would it be possible to ignite it, converting the methane oceans to H2O with a CO2 atmosphere, which could in turn cause photosynthesis to naturally occur? If it's possible, it...

Homework Statement This is a problem from my Statistical Mechanics book by Pathria. [/B] At ##t=0##, the ground state wavefunction of a one-dimensional quantum harmonic oscillator with potential ##V(x)=\frac{1}{2}\omega_0^2 x^2## is given by, \psi(x,0)=\frac{1}{\pi^{1/4}...

Is Dark Energy a constant ? arXiv:1503.04923 [pdf, ps, other] Is there evidence for dark energy evolution? Xuheng Ding, Marek Biesiada, Shuo Cao, Zhengxiang Li, Zong-Hong Zhu Comments: 8 pages, 2 figures. Accepted for publication in the ApJL Subjects: Cosmology and Nongalactic Astrophysics...

Hello, I have a problem where I'm given the following H=-\frac{\hbar\Omega}{2}\sigma_x\quad\quad\quad\textrm{and}\quad\quad\quad\Psi(0)=\left|0\right\rangle\quad Where \sigma_x=\begin{pmatrix}0 &...

The first is taught universally (as far as I can make out) at school and university, that Galileo discovered that all bodies (at least in vacuum) fall at the same rate. He didn't. He read it in Lucretius' great work of Roman science "De Rerum Natura" published about 60 BC. Lucretius followed...

Hi PF there is one thing that i cannot understand here. Please look at eqn 1068 I try to compute the first term (without ##V^\dagger##) I get something like ##c_f (t) =-i/\hbar exp [i(\omega + \omega_{fi})t/2] \frac{sin(\omega + \omega_{fi})t/2}{(\omega + \omega_{fi})/2} \}## Unlike eqn 1071...

What differentiates a homo erectus from a neanderthal? They look very similar as they both lack chins and have brow ridges. To me, a neanderthal seems like a large brained homo erectus. Modern human skulls, on the other hand, look completely different. Thanks

Hey there, before I start I just want to point out that I'm a statistician and doesn't know much about biology. I've worked with artificial neural networks, which required a minor understanding of some biological concepts, but apart from that, my level of knowledge in biology is very limited. I...

Greetings all, First time poster and an absolute neophyte, please forgive my utter cluelessness in advance. So I was reading "Why does the Milky Way rotate?" (http://phys.org/news/2015-02-milky-rotate.html), and it brought to mind a question that's niggled at me every so often when my...

I had a small question, which one contributes more to evolution: 1)short term adaptation and heritable 2)long term adaptation and heritable ?

Hello, Brain corals, like my avatar's Diploria, get their moniker for visually obvious reasons. I wonder whether there are informed hypotheses how come they look that way. The answer to such a question would probably be partly a morphology/pattern formation story, and partly an adaptive story...

Homework Statement A strand of length L begins life as all A's. Assume that each letter evolves independent of all the rest until today, 1000 generations later. Within each generation there is a ##\mu## probability that the letter mutates to either C, G, T. Finally, assume that once a letter...

Homework Statement A quantum system with a ##C^3## state space and a orthonormal base ##\{|1\rangle, |2\rangle, |3\rangle\}## over which the Hamiltonian operator acts as follows: ##H|1\rangle = E_0|1\rangle+A|3\rangle## ##H|2\rangle = E_1|2\rangle## ##H|3\rangle = E_0|3\rangle+A|1\rangle##...

Action potential is defined as" the local voltage change across the cell wall as a nerve impulse is transmitted" Now my question is "why it happens? i.e.,why organism evolves?

Hi all, I'm attempting to prove that i \frac{d \xi (t)}{dt}=[\xi(t),H(p,q ; t)] where the Hamiltonian is explicitly time-dependent, in general. We also have some unitary U(t) which generates time-evolution. I wrote up a quick proof but realized afterward that I had assumed that H and...

Is there any observational data available for evolution of Hubble rate? To give some context, read the dark energy FAQ by Sean Caroll here. He says: "If the universe is decelerating, the Hubble constant is decreasing. If the Hubble constant is increasing, the universe is accelerating. But...

Is physical weakness the catalyst that started Human evolution?

Hello everybody, I'm trying to understand if is possible to say something about the Floquet exponents, in the limit of a very slow changing on time. I try to explain. Given the differential equation $$ \dot{\vec{v}}(t) = A(t) \vec{v}(t) $$ with $$ A(t+T)=A(t) $$ a monodromy matrix is given...

It may not be the general case but this is what it seems from experience. But what's the reason? Do looks indicate health or any other desirable characteristics?

Life started from a single cell, right? And now we have countless number of cells on our planet. So is this like new matter being created? So there is more energy on the planet as of now? How is the energy on the planet being conserved? I possibly framed the question wrong, but I hope you...

Homework Statement Consider the Lagrangian, L, given by L = \partial_{\mu}\phi^{*}(x)\partial^{\mu}\phi(x) - m^2\phi^{*}(x)\phi(x) . The conjugate momenta to \phi(x) and \phi^{*}(x) are denoted, respectively, by \pi(x) and \pi^{*}(x) . Thus, \pi(x) = \frac{\partial...

Homework Statement A quantum system has Hamiltonian H with normalised eigenstates ψn and corresponding energies En (n = 1,2,3...). A linear operator Q is defined by its action on these states: Qψ1 = ψ2 Qψ2 = ψ1 Qψn = 0, n>2 Show that Q has eigenvalues 1 and -1 and find the...

Homework Statement A magnetic field pointing in ##\hat{x}##. The Hamiltonian for this is: ##H= \frac{eB}{mc}\begin{pmatrix} 0 & \frac{1}{2}\\ \frac{1}{2} & 0 \end{pmatrix}## where the columns and rows represent ##{|u_z\rangle, |d_z\rangle}##. (a) Write this out in Dirac...

Anyone exposed to academic rigor would find the use of the term "biological evolution" to be rather vague. There is something about Darwin and common descent and then it starts to get somewhat vague. Is there a definitive definition of "biological evolution"? I offer this in the spirit...

Hi guys, Sorry if this isn't quite the right place to post this, but I have a few conceptual questions that I'd like to clear up about time evolution of a quantum state. Firstly, what is the exact argument for the evolution operator \hat{U}\left(t,t_{0}\right) being independent of the initial...

Given The Hawking-Hartle state is an initial state of the very early universe If the universe very far in the future asymptotically approaches 0K, what is the name of this final state of Maximum Entropy Does time stop at Maximum Entropy final state of the universe Given the assumption that...

Hi all, I was wondering if anyone could clarify my understanding of unitary time evolution of quantum states, in particular for products of time evolution's: Suppose we know state of a quantum system at t=t_{0}, given by \vert\psi\left(t_{0}\right)\rangle, then to determine its state at...

Homework Statement I am trying to solve Problem 21 from this sheet: Homework Equations The equation describing the time evolution of operators is given in the problem. The Attempt at a Solution I have found the commutators of the position and momentum operator with the...

Homework Statement A box containing a particle is divided into a left and right compartment by a thin foil. The two orthonormal base kets |L> and |R> stand for the particle being in either the left or the right compartment, respectively. Hence, any state ket in our system can be...

I think "physics" forum is not the place to find a discussion on evolution. I am hoping someone can point me to a place where evolution is discussed. Let me be clear I do not want a discussion of whither evolution is real. I am looking for a group of people ALL of who accept evolution to discuss...

The question is to calculate the time evoution of S_{x} wrt <\Psi(t)\pm l where <\Psi\pm (t) l= ( \frac{1}{\sqrt{2}}(exp(^{+iwt})< \uparrow l , \pm exp(^{-iwt})< \downarrow l ) [1] Sx=\frac{}{2}(^{0}_{1}^{1}_{0} ) Here is my attempt: - First of all from [1] I see that l \Psi\pm (t) > = (...

Dear friends, I am writting a simple essay about the mechanisms of scientific evolutions, where I would like to point out the main driving forces that induce scientific progress. I would like to give simple examples from history of science (e.g Physics, Astrophysics, Mathematics, etc.)...

I spoke to someone that said that the reason we know humans originated from evolution is because there is no other scientifically possible explanation. I originally thought the reason we knew humans originated from evolution because we had explicit evidence of human evolution. Although now that...

I'm curious about what debates are currently going on within the scientific community. Are there still things about evolution that scientists don't understand or agree upon? Links/sources would be greatly appreciated!

Homework Statement Consider a time-dependent harmonic oscillator with Hamiltonian \hat{H}(t)=\hat{H}_0+\hat{V}(t) \hat{H}_0=\hbar \omega \left( \hat{a}^{\dagger}\hat{a}+\frac{1}{2} \right) \hat{V}(t)=\lambda \left( e^{i\Omega t}\hat{a}^{\dagger}+e^{-i\Omega t}\hat{a} \right) (i)...