I have a degree in math and a degree in cs. I fucking love nonsense.

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Cake day: June 14th, 2023

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  • Vigier is pretty famous for making fretless guitars but they are also pretty pricey afaik. It’s not particularly hard to convert an existing guitar if you have any glass workers in your area willing to cut a mirror board.

    I did roughly this way back in 2009 on a cheapo strat clone with a bolt-on neck:

    1. Have a piece of mirror cut in the shape of the fretboard on the current neck.

    2. Remove the frets from your old fretboard with pliers.

    3. Fill the fret slots with wood filler.

    4. Sand the whole thing down flat.

    You can remove the fretboard entirely to swap it with the mirror board if you like, but sanding the whole thing down to the desired height seemed simpler to me at the time. You also retain vaguely useful “guide” marks from where the fret slots used to be with this approach.

    Note that the height/width of your new board needs to play well with your nut/bridge height and whether or not you removed the old board. You also want a piece of mirror thick enough not to crack.

    1. Epoxy the mirror board to the neck.

    2. Sand off any excess epoxy and buff the sides smooth.

    This approach worked okay for me at the time. I don’t recall any exact materials or measurements I used since I did this over a decade ago. I mostly just winged it and tried to use common sense.

    I will say the whole process is pretty finicky. A lot of small things contribute to playability in general. Choice of strings (roundwound, flatwound, different gauges), nut/bridge height, truss rod adjustments, neck shims etc. There’s also the worry of cracking the glass from an overzealous truss rod adjustment and effectively breaking the whole neck (though this never actually happened to me).

    The main issue I noticed playing fretless electric is that sustain is reduced. On a typical electric guitar the string vibrates between the metal fret and bridge materials (ignoring the nut). These materials are fairly hard, but on a fretless instrument the string vibrates between your much softer finger tips and the bridge. Perhaps a compressor pedal or some type of sustainer system would help?

    If you pay attention to vigier recordings they tend to do really well with sustain. So their typical setup might be worth researching and trying to mimic.

    For a toy DIY project to experiment with it’s fairly fun, but I wouldn’t expect anything game changing. Getting a nice sounding + nice to play set-up is challenging and involves a lot of nitty-gritty details.

    As a side note, you could technically stop at step 4, though you’d probably want to sand things to a particular radius rather than flat. This is a common approach bass players take to convert fretted basses to fretless basses. There are many guides on how to do this online.

    Disclaimers: This was something I did nearly 15 years ago as a teenager after reading quite a lot of random internet posts on it. Don’t use my rambling as a source if you decide to try this. Use a real guide (there are many for fretted to fretless bass conversion guides that would apply for the first 4-ish steps for example). I am not responsible for gear you break or money you waste.

    You could also just buy a slide for cheap if you’re into that.






  • Operating System Concepts by Silberschatz, Galvin and Gagne is a classic OS textbook. Andrew Tanenbaum has some OS books too. I really liked his OS Design and Implementation book but I’m pretty sure that one is super outdated by now. I have not read his newer one but it is called Modern Operating Systems iirc.


  • myslsl@lemmy.worldtoScience Memes@mander.xyzI just cited myself.
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    1 year ago

    i has nice real world analogues in the form of rotations by pi/2 about the origin (though this depends a little bit on what you mean by “real world analogue”).

    Since i=exp(ipi/2), if you take any complex number z and write it in polar form z=rexp(it), then multiplication by i yields a rotation of z by pi/2 about the origin because zi=rexp(it)exp(ipi/2)=rexp(i(t+pi/2)) by using rules of exponents for complex numbers.

    More generally since any pair of complex numbers z, w can be written in polar form z=rexp(it), w=uexp(iv) we have wz=(ru)exp(i(t+v)). This shows multiplication of a complex number z by any other complex number w can be thought of in terms of rotating z by the angle that w makes with the x axis (i.e. the angle v) and then scaling the resulting number by the magnitude of w (i.e. the number u)

    Alternatively you can get similar conclusions by Demoivre’s theorem if you do not like complex exponentials.


  • myslsl@lemmy.worldtoScience Memes@mander.xyzI just cited myself.
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    1 year ago

    They don’t eventually become 1. Their limit is 1 but none of the terms themselves are 1.

    A sequence, its terms and its limit (if it has one) are all different things. The notation 0.999… represents a limit of a particular sequence, not the sequence itself nor the individual terms of the sequence.

    For example the sequence 1, 1/2, 1/3, 1/4, … has terms that get closer and closer to 0, but no term of this sequence is 0 itself.

    Look at this graph. If you graph the sequence I just mentioned above and connect each dot you will get the graph shown in this picture (ignoring the portion to the left of x=1).

    As you go further and further out along this graph in the positive x direction, the curve that is shown gets closer and closer to the x-axis (where y=0). In a sense the curve is approaching the value y=0. For this curve we could certainly use wordings like “the value the curve approaches” and it would be pretty clear to me and you that we don’t mean the values of the curve itself. This is the kind of intuition that we are trying to formalize when we talk about limits (though this example is with a curve rather than a sequence).

    Our sequence 0.9, 0.99, 0.999, … is increasing towards 1 in a similar manner. The notation 0.999… represents the (limit) value this sequence is increasing towards rather than the individual terms of the sequence essentially.

    I have been trying to dodge the actual formal definition of the limit of a sequence this whole time since it’s sort of technical. If you want you can check it out here though (note that implicitly in this link the sequence terms and limit values should all be real numbers).



  • My degree is in mathematics. This is not how these notations are usually defined rigorously.

    The most common way to do it starts from sequences of real numbers, then limits of sequences, then sequences of partial sums, then finally these notations turn out to just represent a special kind of limit of a sequence of partial sums.

    If you want a bunch of details on this read further:

    A sequence of real numbers can be thought of as an ordered nonterminating list of real numbers. For example: 1, 2, 3, … or 1/2, 1/3, 1/4, … or pi, 2, sqrt(2), 1000, 543212345, … or -1, 1, -1, 1, … Formally a sequence of real numbers is a function from the natural numbers to the real numbers.

    A sequence of partial sums is just a sequence whose terms are defined via finite sums. For example: 1, 1+2, 1+2+3, … or 1/2, 1/2 + 1/4, 1/2 + 1/4 + 1/8, … or 1, 1 + 1/2, 1 + 1/2 + 1/3, … (do you see the pattern for each of these?)

    The notion of a limit is sort of technical and can be found rigorously in any calculus book (such as Stewart’s Calculus) or any real analysis book (such as Rudin’s Principles of Mathematical Analysis) or many places online (such as Paul’s Online Math Notes). The main idea though is that sometimes sequences approximate certain values arbitrarily well. For example the sequence 1, 1/2, 1/3, 1/4, … gets as close to 0 as you like. Notice that no term of this sequence is actually 0. As another example notice the terms of the sequence 9/10, 9/10 + 9/100, 9/10 + 9/100 + 9/1000, … approximate the value 1 (try it on a calculator).

    I want to stop here to make an important distinction. None of the above sequences are real numbers themselves because lists of numbers (or more formally functions from N to R) are not the same thing as individual real numbers.

    Continuing with the discussion of sequences approximating numbers, when a sequence, call it A, approximates some number L, we say “A converges”. If we want to also specify the particular number that A converges to we say “A converges to L”. We give the number L a special name called “the limit of the sequence A”.

    Notice in particular L is just some special real number. L may or may not be a term of A. We have several examples of sequences above with limits that are not themselves terms of the sequence. The sequence 0, 0, 0, … has as its limit the number 0 and every term of this sequence is also 0. The sequence 0, 1, 0, 0, … where only the second term is 1, has limit 0 and some but not all of its terms are 0.

    Suppose we define a sequence a1, a2, a3, … where each of the an numbers is one of the numbers from 0, 1, 2, 3, 4, 5, 6, 7, 8 or 9. It can be shown that any sequence of the form a1/10, a1/10 + a2/100, a1/10 + a2/100 + a3/1000, … converges (it is too technical for me to show this here but this is explained briefly in Rudin ch 1 or Hrbacek/Jech’s Introduction To Set Theory).

    As an example if each of the an values is 1 our sequence of partial sums above simplifies to 0.1,0.11,0.111,… if the an sequence is 0, 2, 0, 2, … our sequence of partial sums is 0.0, 0.02, 0.020, 0.0202, …

    We define the notation 0 . a1 a2 a3 … to be the limit of the sequence of partial sums a1/10, a1/10 + a2/100, a1/10 + a2/100 + a3/1000, … where the an values are all chosen as mentioned above. This limit always exists as specified above also.

    In particular 0 . a1 a2 a3 … is just some number and it may or may not be distinct from any term in the sequence of sums we used to define it.

    When each of the an values is the same number it is possible to compute this sum explicitly. See here (where a=an, r=1/10 and subtract 1 if necessary to account for the given series having 1 as its first term).

    So by definition the particular case where each an is 9 gives us our definition for 0.999…

    To recap: the value of 0.999… is essentially just whatever value the (simplified) sequence of partial sums 0.9, 0.99, 0.999, … converges to. This is not necessarily the value of any one particular term of the sequence. It is the value (informally) that the sequence is approximating. The value that the sequence 0.9, 0.99, 0.999, … is approximating can be proved to be 1. So 0.999… = 1, essentially by definition.




  • myslsl@lemmy.worldtoScience Memes@mander.xyzI just cited myself.
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    1 year ago

    Yes, informally in the sense that the error between the two numbers is “arbitrarily small”. Sometimes in introductory real analysis courses you see an exercise like: “prove if x, y are real numbers such that x=y, then for any real epsilon > 0 we have |x - y| < epsilon.” Which is a more rigorous way to say roughly the same thing. Going back to informality, if you give any required degree of accuracy (epsilon), then the error between x and y (which are the same number), is less than your required degree of accuracy




  • myslsl@lemmy.worldtoScience Memes@mander.xyzeigenspaces
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    1 year ago

    Eigenvectors, values, spaces etc are all pretty simple as basic definitions. They just turn out to be essential for the proofs of a lot of nice results in my opinion. Stuff like matrix diagonalization, gram schmidt orthogonalization, polar decomposition, singular value decomposition, pseudoinverses, the spectral theorem, jordan canonical form, rational canonical form, sylvesters law of inertia, a bunch of nice facts about orthogonal and normal operators, some nifty eigenvalue based formulas for the determinant and trace etc.


  • myslsl@lemmy.worldtoScience Memes@mander.xyzeigenspaces
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    1 year ago

    My experience with eigenstuff has been kind of a slow burn. At first it feels like “that’s it?”, then you do a bunch of tedious calculations that just kind of suck to do… But as you keep going they keep popping up in ways that lead to some really nice results in my opinion.


  • myslsl@lemmy.worldtoScience Memes@mander.xyzhmmmm
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    1 year ago

    Oh okay.

    If there are infinite numbers, then there’s 3 in there somewhere.

    No, this is not true. Just because you have infinitely many numbers in some collection, doesn’t mean one of the numbers in your collection has to be 3.

    Look at the number line. There are infinitely many numbers on the number line between 1 and 2. For example 1+1/2, 1+1/4, 1+1/8, … are in there (among many others). But all of the numbers between 1 and 2 are strictly smaller than 3, so none of them can be 3.

    Alternatively, there are infinitely many numbers strictly smaller than 3, none of which are 3 either.

    If 3 is not there then it’s not infinite.

    Well consider the set of numbers 3+1, 3+2, 3+3, 3+4, … (the set of integer numbers strictly larger than 3). This set of numbers is also infinite and does not contain 3. So a set being infinite doesn’t imply it must contain the number 3.



  • myslsl@lemmy.worldtoScience Memes@mander.xyzhmmmm
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    1 year ago

    “The cardinality of the integers is equal to the cardinality of the real numbers, which is called the continuum hypothesis.”

    The cardinality of the integers is not equal to the cardinality of the reals. The integers are countable (have the same cardinality as the natural numbers). A very famous proof in set theory called Cantor’s diagonal argument shows the reals are uncountable (i.e. not countable).

    The continuum hypothesis is also not about comparing the cardinality of the reals and the integers or naturals (since we already know the above). The continuum hypothesis is about comparing the cardinality of the reals with aleph_1.

    Within the usual set theory of math (ZFC set theory), we can prove that we can assign every set a “cardinal number” that we call its cardinality. For finite sets we just assign natural numbers. For infinite sets we assign new numbers called alephs. We assign the natural numbers a cardinal that we call aleph_0.

    These cardinal numbers come with an ordering relationship where one set has a cardinality larger than another set if and only if its associated cardinal number is larger than the other sets cardinal number. So, alepha_0 is larger than any finite cardinal, for example. There is a theorem called Cantor’s theorem that tells us we can continually produce larger and larger infinite cardinals in fact.

    So, we know the reals have some cardinality, thus some associated cardinal number. We typically call this number the cardinality of the continuum. The typical symbol for this cardinality is a stylized (fraktur) c. Since aleph_0 is countable, every aleph after aleph_0 is uncountable. By definition aleph_1 is the smallest uncountable cardinal number. The continuum hypothesis just asks if aleph_1 and c are equal.

    As an aside, it is provable that c has the same cardinality as the powerset of the naturals. We let the cardinality of the powerset of a set with cardinality x be written as 2^x. Then we can write the continuum hypothesis in terms of 2^{aleph_0} and aleph_1. The generalized continuum hypothesis just swaps out 0 and 1 for an arbitrary ordinal number alpha and its successor in this new notation.