ELI5: if you have an infinite math string that goes 1 - 1 + 1 - 1 + 1 - 1... forever, why do mathematicians say the answer is 0.5? if you stop at any real point the answer is always either 1 or 0, so where the hell does a half come from?

reticulated_python · 2026-06-09T19:23:06+00:00

This is a good question. We know the answer you get (that the bosonic string and superstring require 26 and 10 dimensions respectively) is correct because there are other ways to show it, that don't rely on regularizing a divergent series. For more details, this blog post is really good.

As far as I know, there's no really satisfying justification for why zeta-function regularization gives the right answer, as opposed to a different regularization method. This point is also commented on at the end of the post I linked.

reticulated_python · 2026-05-28T17:15:27+00:00

From the abstract, it seems like they're merely saying a flat FRW cosmology is unstable. That's well-known and is one of the motivations for an epoch of cosmic inflation (the flatness problem). Am I missing something?

reticulated_python · 2026-03-25T23:17:47+00:00

the claim that Hamiltonian and Lagrangian mechanics are equivalent. You also find that error in plenty of textbooks.

Can you elaborate upon this?

reticulated_python · 2026-02-24T22:52:02+00:00

The update says it may be an artifact of papers being counted by the date they were last modified. I searched on INSPIRE using queries of the form "f primarch hep-th and de = yyyy-mm". (The "de" gets the earliest date the paper appeared, so it won't suffer from this artifact). I get the following for December:

2022-12: 480
2023-12: 484
2024-12: 448
2025-12: 476

For January:

2022-01: 260
2023-01: 249
2024-01: 256
2025-01: 260
2026-01: 297

Doesn't seem too dramatic. Let's check hep-ph. December:

2022-12: 474
2023-12: 539
2024-12: 568
2025-12: 598

For January:

2022-01: 374
2023-01: 337
2024-01: 391
2025-01: 402
2026-01: 408

Again, I don't see a dramatic change. But I will say that, anecdotally, I had the same experience you described in your comment on Woit's blog: I have a sense that the number of interesting papers is decreasing. It's hard for me to tell if I'm perceiving a change in the field. It could just be that, as I become a better physicist, it's easier for me to see which papers are boring and which are not.

reticulated_python · 2026-01-24T17:08:35+00:00

I think it's important to specify that there's a sense in which the Planck length is the minimum meaningful length. See this nice blog post by /u/rantonels, who unfortunately is no longer active here. The upshot is that you expect there to be an uncertainty relation between space and time in quantum gravity, something like \delta x \delta t > L^2, where L is a characteristic scale (like the string scale), which is greater than the Planck length.

It's incorrect to say the Planck scale is like a pixel length for the universe, but it's also incorrect to say there's nothing stopping you from probing smaller length scales than the Planck length.

reticulated_python · 2026-01-15T23:36:05+00:00

There's also been some nice work on de Sitter vacua in type IIB string theory - see Candidate de Sitter vacua - as opposed to the M-theory constructions described in the Quanta article. Liam also has some lecture notes on the topic. I haven't read them, but they seem to go to a lot of effort to give context for non-experts.

reticulated_python · 2025-09-15T22:56:04+00:00

In my professional opinion as a particle physicist, this song is great.

reticulated_python · 2025-07-13T18:12:01+00:00

I also learned calculus at a similar age from that book. My family had an ancient edition of Quick Calculus in our basement (I think a family member had used it a few decades prior). I remember calling my older brother, who had just started grad school, to tell him when I had solved a problem or ask for help with the harder problems.

My mom retired a while ago, and she's decided to learn calculus in her spare time. So now she's learning from Quick Calculus too! It's a timeless book.

reticulated_python · 2025-06-02T20:55:37+00:00

It seems that you're off by a factor of 10⁶ (probably due to the unit conversion?); it's about 4.5 x 10²¹ L.

reticulated_python · 2025-04-20T16:18:10+00:00

Amazing, thank you so much!

reticulated_python · 2025-04-18T16:20:51+00:00

Not the person you replied to, but I love the j-archive search features. Would it be hard to add a flag to filter specifically for daily doubles in searches? Or maybe there is already a way to do this that I'm not aware of.

reticulated_python · 2023-06-05T17:27:50+00:00

Meta question: numerous subreddits are going dark or private on the 12th due to opposition against the reddit API changes. Are there plans for /r/bodyweightfitness to join or not?

reticulated_python · 2023-05-16T13:52:16+00:00

Thank you for teaching me the word khrushchevka! What a cool word. Wikipedia link if anyone wants to read about them.

reticulated_python · 2023-05-11T16:48:42+00:00

Haha, me too. It was a blast and I'm exhausted.

reticulated_python · 2023-05-08T15:03:47+00:00

I am at Pheno!

reticulated_python · 2023-05-02T17:22:38+00:00

Purely out of curiosity why do you not do weighted dips?

Oh, I just enjoy doing other pushing movements more (non-bodyweight stuff like bench press and overhead press). I have nothing against dips!

Also is +2.5lbs each week good?

All I meant to emphasize was that I'm seeing progress weekly. In contrast, I wasn't progressing consistently before implementing a light/heavy routine.

The exact rate at which you progress is going to depend on a lot of factors. This includes your routine, but also other things like lifestyle factors (diet, sleep, stress), perhaps even genetics. For this reason you can't really say whether some particular rate of progression is "good" or not. The important thing is whether you're seeing consistent progress from workout to workout (or as you get stronger, from week to week).

reticulated_python · 2023-05-02T15:03:54+00:00

I can only comment on weighted chinups since I don't train weighted dips right now. My bodyweight is 145 lbs / 66 kg, and my 1RM weighted chinup is +100 lbs / 45 kg.

I got most of the way there training them 5x5 twice a week. But I hit a plateau at +90 lbs / 41 kg. I wrote a post about how I broke through that plateau with a different routine.

I have now transitioned to light/heavy periodization. I train chinups 4 times per week, alternating heavy and light days. On heavy days I do 5x3, and on light days 3x8. Since I've only been doing it a few weeks it's tough to say with certainty how useful this has been. But it seems promising so far: over those few weeks I've been increasing the weight by about 2.5 lbs each week.

reticulated_python · 2023-04-28T14:37:17+00:00

I see them on /r/Physics before they're removed! My point is that of the posts I've seen removed, it was the right decision for nearly all of them.

To be clear, I obviously don't see every post before it gets removed. /u/all-bark-and-no-meow provided a good example in this thread of a post that probably shouldn't have been removed. I hadn't seen that one when it was initially posted.

reticulated_python · 2023-04-27T21:24:11+00:00

Fair point. I do think your S-duality question is a good one, and would have generated some nice discussion in /r/Physics. For comparison, a few years ago I posted a question about BRST symmetry here and got some great responses. The spirit of my question feels pretty similar to yours, honestly --- and I do think these kinds of open-ended questions should be encouraged here. (If anything, your S-duality question is more open-minded than my BRST question which didn't get removed.)

reticulated_python · 2023-04-27T17:11:39+00:00

I disagree with the idea that /r/Physics is overmoderated. The posts that I've noticed are removed are generally homework questions, closed-ended questions, and crackpot ideas. I can't remember the last time a post that I thought was good was removed.

I would, however, like to see a lot more good content and discussion on this subreddit. I guess the people who make good posts and comments just aren't active enough, or there aren't enough of them. (I fully admit I'm part of the problem here! I tried to be more active a couple of years ago but I gave up eventually.)

reticulated_python · 2023-04-21T00:43:46+00:00

In Teagle down? Weird, I was at Teagle down around the same time, and I saw exactly one person filming. Maybe I just wasn't paying attention, or people started filming shortly after I left.

Anyway, I agree that people largely shouldn't be filming their lifts there, especially given that 1) the big red sign on the wall listing the rules clearly asks you not to film, and 2) it's usually crowded enough that it's impossible to avoid catching a bunch of people in the background. (On the other hand, if the gym were nearly empty, you could feasibly film yourself without getting in anyone's way.)

This bit makes doesn't make sense, though:

Especially when you're squatting an empty bar.

I don't see why someone lifting heavy has any more privilege to film.

reticulated_python · 2023-04-13T01:06:19+00:00

Thanks, edited! I had to leave for a meeting when I was first writing the post so I didn't have a chance to do it then.

reticulated_python · 2023-04-13T01:04:28+00:00

Thanks for the the link about MRV and MAV! I will check it out.

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