When in doubt cold calling european researchers, use English or Spanish
In other news, this week's NewScientist have a couple of interesting thoughts that is quite counter to my intuition:
1. About the LIGO gravitational wave business that should have been reported many years earlier, it appears the NewScientist team have been involved in uncovering irregularities in some data collected by research institutes. LIGO's response reminds of what the general public think of the government, but I trust they are actually doing things about it
The NS article is a storm in a teacup. Some researchers have attempted to re-analyse the LIGO data, failed, then claimed LIGO didn't observe anything. Which is funny seeing as how the neutron star merger was also observed optically.
But a result is that LIGO will publish details of how to do the analysis, which is good.
Indeed, that's how science keeps itself in check. Looks like we can benefit from these independent investigators in keeping our integrity in check. Most data faults are often accidental though, caused by human errors and other unconscious things
after all, it is really hard work to crawl through all that data, even with advanced AI
2. It turns out mass air travel has a mixed effect to pandemic spreading. Common wisdom said that air travel should result in pandemics to spread much quicker before a warning signal is evident, but the latest research suggested that because pandemics often begins with local strains getting some mutation and become deadly, and people infected with the less deadly ones can get some shielding effects from the genetically similar ones, air traffic actually would have spread these mutants all over the globe, thus in a way vaccinate people globally making them harder to suddenly get all sick unl…
3. In regards to taming extreme weather,warming climate models showed changes the jet stream in such a way that it can triple heatwaves and floods. Interestingly, while cutting sulfur pollution from coal burning can stop this rise and stop arctic shrinkage, the decrease in the cooling effect by them on the mid lattitudes can make stronger heatwaves and storms there
4. And finally, the main topic of this weeks NS is that too much self control can lead to regret and other things
All 4 of these topics caught my attnetion because they all share this "It looks like it is X, but actually, it is Y and -Y" property
Abstractly speaking, being exposed to these problem solving scenarios and case studies can be useful in brainstroming solutions, because of the inherent complexity and that they are opposite (not just different) from our common sense. Most of our modern issues including the messy political sphere all have some traits of these and thus solution that can tailor to these "problem profiles" can be very effective, I think
It seems to me that the current trend of our society is that we increasingly need to employ solutions that go against our common sense, plus some suitable mixture of common sense to spice it, in order to untangle the problems and reach a solution
@Secret actually when I read message in this room, I sometimes experience that. So communicating on web is really different from face-to-face conversation.
so I think rebuking others on web may not be that effective as doing that in reality.
people may just overlook some of your sarcastic phrases.
also, I don't know how to express tones in wriiten English.
@rob I mean the tone of talking. When I speak, I can express my emotion in corresponding tones, but when I write, I can't. The same sentence with different tones often conveys different meaning, like good-willed or ill-willed.
Sorry, I'm using the chat for the first time so I'm not sure if this is the right place but does anyone have thoughts on Sandu Popescu's recent note on the arxiv? arxiv.org/abs/1811.05472
@user1936752 (welcome) hes a very prolific and diverse researcher/ writer. like some his attn to bell nonlocality, bohmian mech, interpretations of QM foundations, & collaborations with aharanov etc. yes there is something very subtle about the density formulation of QM. it naturally leads to realist interpretations. few have the virtuosity/ tenacity to pursue it to the end. arxiv.org/search/…
LIGO is revolutionary new science and uses very new techniques/ methods of analysis. the detectors are incredibly sensitive and can apparently pick up earthquakes and maybe even nearby trucks/ traffic. the data analysis is a triumph of data science. did feel their process is somewhat opaque so far. LHC sometimes has similar troubles with false positives and very subtle statistical analysis. science in progress...
In that case I'm not whether I should be talking about four-vectors as it might just be confusing, though if you go on to take any serious SR course you'll learn about them since they're pretty fundamental.
In special realtivity we are dealing with four dimensional spacetime not just three dimensional space, so vectors have a time component as well. So the four-momentum is $(p_t, p_x, p_y, p_z)$, where the time component is $p_t = E/c$ ($E$ is the total energy).
In SR the magnitude of a four vector is called the norm. It's calculated in a slightly different way to the magnitude of a three-vector. For a four-vector the norm is given by:
@enumaris I wouldn't worry too much about it. Interviewers are normally interested in whether you know what you are talking about rather than in a specific problem.
you can also realize the answer by looking at X-3Y>0 and noticing that nowhere on the left hand side does the joint probability's mean move away from 0
That said, the way you'd do the integral is kinda funny. The only way I know how to do it is to take a partial derivative under the integral sign, compute the integral, and then integrate
Denote the pdf of normal distribution as $\phi(x)$ and cdf as $\Phi(x)$. Does anyone know how to calculate $\int \phi(x) \Phi(\frac{x -b}{a}) dx$? Notice that when $a = 1$ and $b = 0$ the answer is $1/2\Phi(x)^2$. Thank you!
lol, yeah: Integrate[ CDF[NormalDistribution[0, 1], x] PDF[NormalDistribution[0, 1], x + 1], {x, -\[Infinity], \[Infinity]}] fails to give a closed-form solution
but the closed-form is just $\frac12(1+\text{erf}(1/2))$
So that's a touch pathetic on the part of mathematica
Thank you for your interest. The problem with my thesis proposal is that it requires a good knowledge of some theoretical courses that you may have not taken: advanced QFT, supersymmetry and supergravity and introduction to string theory (besides particles physics of the Standard Model end Beyond, GR and cosmology). If you think you can compete for a fellowship in EDPIF, you can send me a detailed CV with grades of the last years and a list of corses that you have taken.
@Slereah who has chance to take these courses? I have never seen any of them taught in either of my undergraduate or graduate school. I even have never taken general relativity. It was not taught throughout my registered academic years. I consider those subjects are for people who research on them to self-study.
I don't particularly like to go to lectures because I found most of my professors in my garduate school didn't teach lectures eaily to follow.
either because their accents are strange, or they presume students have read the textbooks before their courses, or they just can't express science in an understandable ways.
I actually took course based on my own interests rather than research need because my advisor never gave advice about what courses are helpful for research.
Yeah I didn't either. But I think I may have taken all my electives by the time I was doing research. I kind of regret not taking extra electives though
Especially since one of my electives was an astro course that I just hated
Well mine was undergrad, so more courses and less research. But still not a ton of time to take electives with all the non-physics courses that were required
but in undergraduate school, I did have taken all electives I can take because 4 years without research is really too long; if not taking courses there is too much free time.
And we had a pretty big focus on undergrad research, so I was involved in it most of my 4 years. I thought it was common, but looking back I can only think of a handful of classmates that did the same
@danielunderwood I did consider dong research in undergraduate but my undergraduate school didn't have professors conducting research of my interests; most of their research are very applied rather than theoretical.
@CaptainBohemian we were required to take a good many, but I don't think it's like that outside of the US from what I hear. I wasn't a huge fan, though there was a history course that I enjoyed a good deal
@vzn basically data science. They call it "algorithm developer" I guess.
@danielunderwood you'd have complex activations, at the end of the day you would have to get those complex activations and translate it to probabilities or some real number
I think how the complex weight would affect your outputs depend on the way you translate the activations to your desired output
but probably the most natural way will simply lead to you having effectively 2n weights
I'm not sure DL4J actually just "ports" python code over to Java tho...I think they actually implemented their library in Java...they just have a way to like...load weights or something? I don't know the backend that well tbh...
I've told to come here by another user after my question was put on hold a few days ago for being "off-topic".
What on Earth does "conceptual" mean? It's a word I see floating around a lot on this site and it's never explained. Ever. I asked the aforementioned user what it meant and they directe...
Though I suppose compile-time allocations may all end up on the stack and be a bit faster (not to mention compiler-optimizable)...that's a good case of premature optimization if I've ever seen it though
@enumaris there are not many (serious) data scientists who would devalue python these days. its quite possible his work was doable with python but he had some kind of bias. on other hand, its not unusual for different environements to have different tools.
bottom line, a very large amount of data science is being done on python now. and it seems to be increasing substantially. also it can be coupled with higher compute resources eg GPUs. so his attitude is basically backward. yeah you run into all kinds during job searches. not every job offered is desirable...! ps have not done a lot of python myself but can see a wave when inundated by it!
Even if you felt the need to do production with something else, I don't see how you could really build models without something like python to prototype in
there is some (historic) bias that dynamic languages (in contrast to compiled ones) arent suitable for production but think its a fading concept. the distinction is blurry anyway. eg java crosses the boundaries etc
someone might argue that some apps push the garbage collection of dynamic memory too hard, but suspect thats more to be seen as bad coding... have worked with very memory intensive apps in java and the (highly tuned!) gc is almost never a factor.
I haven't run into anything where dynamic memory allocation was a problem. There are people that work on platforms with crazy resource restrictions, but I've worked on fairly limited microcontrollers with dynamic allocation being fine
@enumaris the guy may not even know what youre talking about. theres more than 1 way to skin a catâ„¢... dont assume everyone knows what theyre talking about o_O
I've heard some people call python not production grade because it's slow though that's rarely a big issue and especially not an issue if you're just wrapping C calls. Some people may say that because python doesn't require a given structure, so it's a lot easier to write sloppier code as project size increases
Scala should be able to import java libs, but I'd imagine using them can be a pain due to the difference in Java and Scala
In any case, probably if the language of the code is a huge driving force, either they have to have software engineering support to code in Scala, or probably it's not the job for me lol. I'm happy to learn Scala for a job, but it ain't gonna be like "implement a DL framework from scratch in Scala". XD
I will say that python can have issues in that it can run into issues during execution that would be caught by the compiler in other languages. Solid testing should help that though
I think that scala is sold to people as easy to parallelize, which is indeed the case when it comes to functional code. But it's not like it's difficult to write parallel or distributed code in python if you roughly know what you're doing
You could use a numerical estimate in place of backprop, like for each weight $W$ just use $\Delta J/\Delta W$ as your gradient...it's just that doing that for every single weight is computationally inefficient. It's better to calculate $\Delta J/\Delta W$ using the chain rule
XD
You end up with something like $J(A(B(C(...(W)))$ and then you apply the chain rule to that and the expression like $\partial J/\partial A \cdot...\partial A/\partial B...$
is easier to evaluate computationally since you don't have to make a full forward pass to get the answer, you can get it from matrix multiplication
However, I dont have a deep knowledge in this related field to get my questions answered concerning charging a stuff to make them apply repulsive force to push themselves apart. For instance, suppose that two cars are accelerating and about to get crashed. There will be two positive/negative charges
@enumaris yeah that's probably a better description. I was thinking extremum since you could have a global maximum and just negate the function, but that's extra steps. I thought one global minimum would imply everywhere convex though
It's very difficult to sustain any net charge on an object. If you give yourself a charge by shuffling on the carpet, it discharges as soon as you touch anything that it can go to
I don't know that there's too much you can do. If you managed to give a car a charge, it would want to escape. You also can't magically bring this charge out of nowhere, so you'd have to just redistribute the charge that's already on the car. That's going to make any repulsion you have be an attraction elsewhere. If I wanted to make a car stop to prevent an accident, I'd use sensors and a mechanical means of stopping
You could perhaps cook up something with magnets that's less volatile, but I still don't see it working well in the real world
Though I'll also say that I'm no expert in using EM to achieve practical things
You could probably build a toy model with a magnet to see how it works, but doing the same with trying to build a charge could be quite dangerous and I'd suggest against it
Denote the pdf of normal distribution as $\phi(x)$ and cdf as $\Phi(x)$. Does anyone know how to calculate $\int \phi(x) \Phi(\frac{x -b}{a}) dx$? Notice that when $a = 1$ and $b = 0$ the answer is $1/2\Phi(x)^2$. Thank you!
