darklight03/StackMIAsub huggingface dataset:
This is a follow up to a previous question. I use pandoc to create PDFs from markdown files, which uses pdflatex behind the scenes. After a bunch of system upgrades, the type in my printed PDFs started to look off.The weight was heavier, and the the kerning was bunched up. At first I thought this might be a problem with LaTeX or my MacTex install, but now I believe it's a problem with MacOS. When I print on MacOS via Preview or Acrobat, I get the font that looks janky.If I switch to a windows machine and print there (just via the Edge web browser) the type matches more closely to what I see on the screen and used to see when printing from my Mac. I now think the "bad" font I see is just good old Times New Roman, being substituted as a default. Does anyone here know why PDF viewiers/printers on my mac might not see fonts embded in PDFs generated by pdflatex?
I work in quantum field theory in curved spacetime. Within QFTCS, we have a bunch of phenomena showing that the notion of "particle" is quite subtle. For example, the Unruh effect let's us know that the notion of particle is actually observer-dependent. As a consequence, I tend to be quite skeptic about fundamental theories that rely too much on the notion of particle. While I am far from being an expert in string theory, the things I've heard about it make me feel as if that is precisely what string theory does: to take the notion of particle seriously and change it into a quantum string, which would then be able to solve numerous problem within quantum field theory and quantum gravity. I have also heard one or two words about "string field theory", which appears to be a quantum field theory with infinitely many fields. The name, of course, also suggests it is somehow related to string theory. With this in mind, my question is: QFT is a theory about fields, in which particles sometimes appear as cute interpretations. Does the same thing happen in string theory? How exactly (to the best possible presentation for someone who knows nearly nothing about string theory)? Has string theory (or string field theory, or any other similar idea) successfully derived the Unruh effect or is it only "likely to be there" based on being a generalization of QFT?
I have a GRIN lens with the refractive index varying linearly with y, and supposedly this lens tilts the wavefront. Since the rays are travelling normally in both refractive index materials, they stay normal to the plane of the lens at all times. However the wavefront travelling with them tilts because of different speed of light for different indices, and gives a wavefront like this. Is this correct? Or do the rays themselves tilt? I don't think this is a possibility since the rays are always perpendicular to the plane. If my reasoning is correct, does this satisfy Huygens' Law? It states that the wavefront must be perpendicular to the path of the waves at all times, but this doesn't seem to be the case here, which leads me to thinking its the waves themselves that are tilting. Diagrams like this can be found on the internet, but I do not understand how are the waves tilting when they enter normally, What am I missing? I found this situation while solving a problem in a book (Pathfinder for Olympiad Physics) but upon thinking a bit more was fell into this confusing situation.
When one studies representations of (bosonic) Lie groups in physics, whether dealing with spacetime symmetries or gauge symmetries, it is often left implicit whether the representations are over real or complex vector spaces, without acknowledging of course that the representations of an algebra or group can be different over different base fields. A simple example is that the adjoint representation of the Lorentz group is irreducible as a representation over the reals, but reducible when take as a representation over complex vector spaces. When it comes to spinors, often people wish to treat components of spinors as Grassmann variables - this being the 'classical limit' of the fermion anti-commutation relations. My question is whether or not there has been a rigorous treatment of the representations of semi-simple (bosonic) Lie groups over Grassmann-valued vector spaces. EDIT: I suppose the direct analogy I anticipated isn't there. When we allow complex fields, we also allow complex changes of basis. This changes the reducibility of representations, because real Lie algebra elements now can have imaginary components even though the boost/rotation parameter remains real. For Grassmann numbers, it appears that we dont extend the reals as in the complex case, but supercede them. So we dont gain access to a new change of basis like before, where the algebra elements would have Grassmann-valued components while keeping the boost parameters real. Unless I am mistaken and people do work with spinors with "real parts" and "Grassmann parts".
What's the term for a line of dialog that is repeated later in a different context? Christopher Nolan seems to be fond of these lines. In Batman Begins, Ra's first says: Always mind your surroundings And then in the climax Batman says You never learned to mind your surroundings. In The Dark Knight Rises, Bane first says: Then, you have my permission to die as he's breaking Batman, and later Batman claps back with Then, you have my permission to die. Same line, different contexts, often as witty comebacks. I've thought of a couple of possibilities I've heard of, none of which works quite well: Callbacks seem to be a reference to a previous gag, rather than an exact quote. Comebacks and clapbacks can be any kinds of clever retorts, not necessarily the use of your opponent's words against themselves
The general bin-packing problem is NP complete. I have read several papers and other source but I am still not clear about whether a bin-packing problem with a fixed number of bins is NP-hard. Wikipedia says: "Computationally, the problem is NP-hard, and the corresponding decision problem, deciding if items can fit into a specified number of bins, is NP-complete." and later: "On the other hand, bin packing is solvable in pseudo-polynomial time for any fixed number of bins K, and solvable in polynomial time for any fixed bin capacity B." In another paper "Bin packing with fixed number of bins revisited" I have read that for a fixed number of if the sizes of the items are polynomially bounded integers, then the problem can be solved in time n^(O(k)). My specific problem is the following. I have a fixed number of bins m with fixed capacity. The items arrive online. I one case the set of items is known in the other case it is not. Given on what I have read I assume this problem is not NP hard as it could be solved by exhaustive search.
I'm learning about functional programming, In functional programming, functions are treated as first-class citizens, meaning that they can be bound to names (including local identifiers), passed as arguments, and returned from other functions, just as any other data type can. This allows programs to be written in a declarative and composable style, where small functions are combined in a modular manner. -Wiki And.. I started to wonder, how it would be if we tried to adopt this method as foundations to mathematics. Would it be meaningful to consider mathematics with functions being taken as the fundamental object rather than, say, that of the set or non function types? If it is, what would be the difference between the produced mathematics of that procedure, and that we have when we consider sets as the fundamental objects? What would be the advantages/ disadvantages to this approach?
I am seeing many people claiming that cumulus clouds that sometimes form periodic wavy patterns (see images for "altocumulus undulatus" or "Radiatus" for instance) have no explanation aside from being chemtrails, and I'd like to be able to respond with a sound scientific explanation. I'd like to understand the phenomenon and my guess is that it's about the cloud blanket being forced by winds with the result of a periodic pattern appearing, much like sand waves form in shallow water at the beach. But is it really the case? Searching for a more detailed explanation I ran into Tollmien-Schlichting waves that are a path to turbulence, but I admit I did not understand much, so here is my question(s): What is the physics behind such cloud formations? And Given an estimate of the spatial period of these cloud waves and the cloud height, can one infer the windspeed at that height?
If we are moving a block on a rough surface extremely slowly (quasi-statically) with the help of an external horizontal force, then is it the case that no heat will be produced, but the work done by friction force will still be equal to the work done by the external force for any given displacement? The reason this question comes to my mind is, in thermodynamics, if we say that a process is reversible when it is slow, then there should not be any heat production despite having frictional/viscous forces in the system when the process is slow. So, this implies that the existence of a reversible process rests on the idea that friction should not produce any heat. So, it is correct to assume that friction can do work without producing heat when the process is extremely slow? Because if in all the examples we see around, we see that work by friction is always accompanied by heat production. Kindly help.
Suppose we have a system of electrons a very tightly confined space (like a tiny magnetic trap). Let's say we continually increase the degree of confinement such that the electrons are confined into a smaller and smaller space, to the point where the degeneracy pressure reaches a scale comparable to the masses of the other charged leptons. Does there come a point where it's favourable for an electron to "decay" into a heavier lepton due to degeneracy pressure (producing neutrinos and antineutrinos in the process)? My thought is that this process would be somewhat analogous to the formation of a neutron star (or hypothetical quark star). What would happen if we kept confining the particles into a smaller and smaller space to increase the potential further? Would even heavier particles be produced?
Consider a simple experiment, such as boiling water in a pot in your kitchen, is it possible to estimate the time needed for the water to boil based on elementary properties of water ? In the physics and chemistry literatures we find many computational and theoretical works attempting to predict the boiling temperature of water, from elementary properties, such as the molecular bonding strength or angles. But what about the boiling time ? The basic parameters for the boiling time should the heating power, the heat conductivity of the pot, the heat capacity of water, and possibly other properties that characterize the transfer of energy from the environment to the water. My question is about the time needed from the moment where the water temperature is close to boiling point, to the moment where water has left its initial liquid state. It is mentioned in many lectures and textbooks that nucleation is a limiting step in the formation of a new phase, in particular for the boiling of water. But I was never able to find a critical comparison of such statements. So I would appreciate any references or indications. Which kind of computations do you expect to be necessary ? What kind of empirical parameters enter in the calculation ? Was this done in a reference?
Suppose we place a current carrying loop of wire in a magnetic field. Of, course its easy to see that for a uniform field the wire will experience uniform force in all directions and so it'll get stretched out into the shape of a circle. But I wanted to ask if we could make any comments about the shape of the wire, in any random magnetic field without knowing the exact function describing the field. At places where the field is stronger, the wire will tend to get stretched out more so I suppose the local radius of curvature there would be less as compared to a point where the magnetic field strength is lower. But thats just a qualitative rough way of looking at things. Is there some exact way to find out the answer to this
I just started reading about the conduction mechanism in polymer. From what i read, polarons are used as method of charge transportation in non-degenerate polymer. While for degenerate polymer, both charged soliton and polaron will do the job. As i go a bit deeper, polaron can be defined as: A polaron can be thought of as a bound state of a charged soliton and a neutral soliton of which the midgap energy states hybridize to form bonding and antibonding levels. A Quasiparticle that is created through the interaction of charged particles ( electron or holes ) with Phonon. If i understand it correctly, the definition of the polaron contradicts with its existance in non-degenerate polymer as non-degenerate polymer doesnt have soliton due to its topological reason. Also, as i am quite new to all these terms (polaron, bipolaron, soliton, charged soliton and phonon), i tend to get confuse and couldnt differentiate each of them precisely in layman terms as most of the literature are mostly explained in what could say too "academic" for a starter like me. Would someone be able to help me clear my confusion? Any help, advice and guidance are really appreciated. Thanks in advance
Basically, as the title says. Maybe this is trivially true or false, but I have not enough intuitions about topological surfaces or aperiodic tilings. To make it a bit more precise - I mean the kind of aperiodic tilings such as Penrose tilings or the tiling generated by the recently found hat tile. By "gluing" the patch into a torus (or some other surface) I mean essentially just like you fold a net into some geometric shape by connecting edges. And the edges should be glued in such a way that all matching rules of the tiling are satisfied. If this is possible - would the resulting "tiling of the surface" also be aperiodic, or could it be made to be? Here I would consider "aperiodic" to mean that there are no non-trivial symmetries between any two tiles on the surface.
I saw a question asking "If the Moon was moved to the surface of the Earth, from how far away on the Earth's surface would it be visible?". (The question says to ignore any other factors like gravity making it smash into the Earth's surface and effectively destroying both bodies). Basically, it's this, I think: We know AB, which is the radius of the Earth, and we know CD, which is the radius of the Moon. AC is the sum of these two. Even though it doesn't really look like it in my sketch, I think that the lines CD and AB are parallel, and that ABE and CDE are both right-angle triangles. We need to work out the angle at A, which we can use as a ratio of the circumference of the Earth (which obviously is another known quantity), to work out the distance around the circle to B. Are my assumptions correct? Is it possible, from those givens, to calculate the angle at A?
EDIT: Completely rewritten because of the 'needs clarity' tag and some useful related questions appearing in the side-bar. I hope this is clear now This answer gives a long list of properties of particles whose value differs by a minus sign when comparing a particle to its antiparticle. We know that anti-particles exist, so apparently for every particle there is a particle where the value of all the properties in this list are 'flipped': i.e. the same magnitude but of opposite sign. My question is: given a particle, say an electron, does there exist a different particle where some of the properties in the list in the linked answer are flipped and some are not? If the answer is no, why is this not possible? If the answer is yes, what is an example of such a pair of particles?
I am beginning to learn some very basic electronics. I was learning how and why lightbulbs light up. It turns out it happens because they have a very thin filament which makes the passage very narrow for electrons so they lose a lot of energy colliding with the molecules making up the filament instead of using it to drive the passage of the current. This causes three things. Voltage drop Decrease in intensity Transfer of the electrons' energy to the atoms making up the filament so they vibrate causing it to heat up, and the energy is also used to excite electrons to a higher energy level momentarily where they release the energy in the form of photons where the lower the wavelength, the brighter the light color and the greater the energy. So the filament also glows and lights up. I am interested in the latter and I have a couple of questions. Why don't the electrons remain in the higher energy levels? Why do they choose to release the energy as photons?
I've been struggling with proposed answers to the twin paradox. I know that an object traveling at relativistic speed ages slower than a stationary object. This must be caused by some interaction with spacetime that leads to a slowing of time. But how does this work when we are looking at relative time dilation between two or more individuals. Imagine a huge crowd of relativistic rockets moving inertially and crossing each other in all directions at different velocities. How can one pilot claim to be younger than another, while the other is younger than a third who is younger than the first? Then it came to me that this all might just be the same as relativistic length contraction where it is only occurs while they are in motion, and all effects stop once they stop moving. Once they stop the only age effects are measured against an earth clock. We know that for kinetic length contraction, the man on the train station platform will see the relativistic train length contracted while the main on the train will see the train station platform length contracted. But the instant the train stops moving, all measurements return to normal. Is it the same with the twin paradox? That any age difference as seen by one pilot over another disappears once the motion stops? And the only real aging is when measured against an earth clock?
Exactly what the title asks. "Diode" comes with it the ideas of depletion layers and forward/reverse biasing and electron-hole recombination, but SPAD physics doesn't seem to be dependent on any of that. You just put a giant electric field on, and as soon as a photon comes and promotes a charge to the conduction band, it gets so much energy that it can knock other electrons out of their atoms, creating the avalanche. In other words the fact that it's "reverse-biased" relative to the doping of the semiconductors seems irrelevant, as does the fact that the reverse-bias is above the breakdown voltage. Could I take a piece of undoped silicon and use it as a SPAD if I put a sufficiently large voltage on it? Or else why is it important that it's a diode?
I have figures which I use in several places, some of them in dark context and some of them light (for example, a my obsidian vault is dark but a PDF of my thesis is light). As such, some of the figures are colored to work in a dark environment, and some in light. But sometimes I want to take a figure from a dark context and use it in a light context, or vice versa. So far I have created a copy of the figure for the light/dark mode by simply inverting the colors. I use color schemes in which this looks mostly fine. But manually inverting the colors and saving a copy is exhausting, and inefficient. I want to do this automatically, and possibly without saving a copy of the original figure. Is there a way to invert the colors of a figure while compiling the output of a latex document? Thanks a lot! Edit: I saw this question, but the answers were basically "you can't". Since the answers are unsatisfactory and the question is VERY old, I thought it would be best to open a new one. But if this is not the custom here, please let me know and I'll ask there instead.
Noether's theorem states that every differentiable symmetry of the action of a physical system with conservative forces has a corresponding conservation law. Energy, however, is not conserved in an expanding spacetime because there is no symmetry on the time axis. This enables dark energy to exist and is the reason that general relativity does not conserve energy (except in symmetric situations). My question is about how this translates to theories of quantum gravity that predict the existence of spacetime that becomes spatiotemporally isolated near the center of a black hole. Examples are white holes, fecund universes, and collapsing wormholes. I know that black holes conserve energy, at least for an outside observer. So can energy be created in a disconnected region of spacetime at the other side of a black hole center for certain theories of quantum gravity? Or does Noether's theorem prevent this? (Bing insists that the theorem applies here, but I don't trust the answer.)
I was taught that there are four types of nouns: singular countable: journey, sheep, child plural countable: journeys, sheep, children singular uncountable: travel, water, fruit plural uncountable: groceries, customs, thanks Some words are only used with: countable nouns: one, two, three, many, number, few uncountable nouns: much, little, good/great deal, quantity, amount Am I right? What about the word 'cattle'? You can say neither 'three cattle' nor 'much cattle'. (According to Practical English Usage) What type of noun is it? If it is an uncountable noun why I can say 'many cattle' but not 'much cattle'? Isn't 'many' used only with countable nouns and 'much' only with uncountable nouns? Also, you might consider 'staff' or 'jeans'. You can say for example 'four staff' but not 'a staff'. (According to Practical English Usage)
While trying to understand General Relativity, I'm struggeling with disentangling coordinates and curvature. The metric tensor contains information on both: coordinates as well as curvature. Curvature is a physical characteristic of spacetime, while the coordinates can be chosen completely arbitrary. Is there a method to disentagle coordinates and curvature? (Stephan Hawking must have had one as he managed to show that the singularity at the event horizon of a black hole is only a coordinate singularity, not a physical one...) I fistly thought that one could simply use cartesian coordinates - and then would be left with only the curvature (in this question: Determinant of metric tensor in Cartesian Coordinates constant in vacuum) However, I was taught there, that cartesian coordinates can only be used in flat spacetime. Now, I'm totally clueless again how to disentangle coordinates and curvature. I'm looking for a tensor/measure/metric/field, where only the physical curvature is in - and no coordinate curvature. Where the coordinates are flat like in a cartesian grid. Where the metric tensor is simply that of a flat spacetime in cartesian coordinates, if the spacetime is flat (Minkowski spacetime).
We know that a complex manifold with a hermitian metric h is Kahler if and only if the corresponding Kahler form (which can be obtained from Hermitian metric) is closed.The complex manifold has an underlying real smooth manifold whose Riemannian metric can be found from the Hermitian metric of the corresponding complex manifold (Re(h)). We also know that a Riemanian manifold is Kahler if and only if there exists a smooth almost complex structure on it which is metric compatible and whose covariant derivative is zero. Now, the question is: if a complex manifold is Kahler then does this imply that the underlying real smooth Riemannian manifold will be also Kahler? I think that it should be Kahler as if the manifold is already Kahler in complex case so there should be no obstruction to the existence of compatible almost complex structure with vanishing covariant derivative.