Does the pigeonhole principle rule out the possibility of losslessly simulating a universe the size of our own?

Say you had a very powerful computer and wanted to run a completely lossless simulation of a universe approximately the same size as our own: $ 10^{80}$ particles.

Each particle in the simulation has properties like velocity, mass, charge, etc. Assuming that your program didn’t use any tricks (like compressing this simulated universe by storing groups of 1000 particles as if they were one), does the pigeonhole principle mean that you would need a computer made out of at least $ n$ particles to losslessly simulate a universe of $ n$ particles?

I say this because I don’t see how it’s possible to store all of the physical properties of a particle on a piece of hardware without using at least one actual, physical particle.

Am I right about this? Does this mean it would be impossible to ever hope we could create a high resolution, lossless simulation with a number of particles similar to the actual number of particles in our universe?

Does the Adventurers League’s “PHB+1” rule also apply to received magical items?

Yesterday, I was playing an Adventurers League game with a Bugbear character (from Volo’s Guide to Monsters). I am aware of the Adventurers League’s PHB+1 rule, which prevents me from using material from other D&D 5e sourcebooks, like Xanathar’s Guide to Everything.

However, I received a magical item that comes from Xanathar’s Guide to Everything, and I’m wondering if I’m now violating the PHB+1 rule or not.

Does the Adventurers League’s “PHB+1” rule also apply to received magical items?

House rule for experience sharing between party members

There are possibly huge gap between caster and non-caster characters in a party. Caster have plenty of options of getting rid of own experience in exchange for various boosts. Item creation, wish making, less expensive XP spells, permanenting useful spells for himself and comrades. That may made him lose XP faster than he can compensate with common adjusting formula for characters lagging in levels.

The general opinion is simple “just by all costful spells in scrolls”. XP is much under-priced and should never be used if it can be substituted with money.

But I have two objections. At first there are companies that gives players not so much gold. At second versatility is a general rule for d&d. You may achieve similar effect with pretty much different means. That also reflects in fantasy world economy.

So I’d like to design some way for willing characters to share their XP. So fighter that could cast no spells would have a way to return favor to wizard that do much enchantment for him.

There is one thing that should be strictly avoided in designed house rule. Players may not be able to force or talk NPC to transfer XP from them. Neglecting this issue will quickly break game session.

So I decided to introduce house rule with two guards.

First guard is amount of XP that may be reallocated by once: 1/2 of total XP earned by the party between two rests.

Second guard is tedious ritual that only willing creature having much time to spare can afford.

Teamwork benefit from PHB2 suits for this perfectly. This ritual would require much time to establish and would occupy team roster slot that may by used for something else useful by parties that have another member specialization. So using the XP sharing benefit would have fair price in discarding other options.

But I need two advices.

  1. Is there any other more preferable way for XP sharing?

  2. What training should look like and what requirements should be put on the task leader and task members if I would opt to use the teamwork benefit path described above?

Is there a rules-consistent way to rule a character trying to grab a snake?

Bad-guy sorceror just cast Summon Monster I and now a Snake has appeared next to a player. The snake is right next to the king, so she wants to make a go at grabbing the snake and cutting off it’s head.

Is there a rules-based way for me work out the roll and DC? I was thinking it’s not a Grapple check, as she’s not really wrestling against a small snake, so maybe it’s an opposed DEX check?

Is there a rule for armed fighter against unarmed fighter?


A player is engaged in a fight with a unarmed peasant in a tavern. The player had a hand weapon.

There is rules about fight between two fighter both unarmed, but I don’t know what happen in case of one fighter having a weapon.

Actually I give the fighter with the weapon an advantage token*, but only because I don’t find rules about this case and want to make it fair.

* A token that add +10% to WS roll

D&D 5e Lair Action Rule Interpretations for Young Black Dragons [duplicate]

This question already has an answer here:

  • Do dragons of all sizes get lair actions and regional effects? 2 answers

Page 89 of the Monster Manual describes Lair Actions and Regional Effects. It says Regional Effects only apply to Legendary Black Dragons but does not say that for Lair Actions. Does that mean Lair Actions can be used for Young and Wyrmling Dragons?

Is there a rule to recalculate the BODY of characters with cyberimplants?

For the Petrify spell, you only take into account the base BODY of the target, and ignore any kind or armor or protection the target may have since the spell targets the flesh only.

Following the basic rules, from the core rulebook, a full cyborg character a la Robocop, despite being not much more than a brain and spine, still has his full base BODY to resist the spell, since the cyber only makes one lose Essence.

Is there a rule that would allow to recalculate the BODY of a character for the purpose of the spell, taking into account the cyberimplants?

Does timestamp protocol following thomas’s write rule allow non-view-serializable schedules in some cases?

I have came across following line in text book (Database System Concepts Textbook by Avi Silberschatz, Henry F. Korth, and S. Sudarshan $ 6e$ ) page no. 686:

Thomas’ write rule allows schedules that are not conflict serializable but are nevertheless correct. Those non-conflict-serializable schedules allowed satisfy the definition of view serializable schedules (see example box).

What I understood from above lines is that every schedule generated by timestamp protocol following thomas’s write rule is view serializable.

Now let’s take following little schedule: $ S: R_1(X), W_2(X), W_1(X)$ .

This schedule $ S$ is allowed under timestamp protocol which follows thomas’s write rule.

And serialization order is $ R_1(X), W_1(X).$

But I was not able to prove that it is view serializable.

Actually I think that it is non-view serializable because,

  1. Consider serial order as $ T_1, T_2$

    Now final value of $ X$ is being written by $ T_2$ . So not equivalent.

  2. Next alternative serial order is $ T_2, T_1$

    here, $ R_1(X)$ will read value of $ X$ written by $ T_1$ not original value which was there before start of both transaction. So this too is not view-equivalent.

What is going wrong here. please help me with this one.

What definition of the noun “threat” do the rule books for D&D 5E use when it affects gameplay mechanics?

I have recently asked a question about Surprise where the unclear interpretation of the word “threat” in the sentence “Any character or monster that doesn’t notice a threat is surprised at the start of the encounter.” seems to be the root of the problem. In a comment to an answer, I was adviced to look at Wiktionary’s entry for “threat” which defines it as:

  1. An expression of intent to injure or punish another.
  2. An indication of potential or imminent danger.
  3. A person or object that is regarded as a danger; a menace.

While meaning 1 is certainly not the relevant one in the context of the rule for Surprise, the confusions seems to stem from the distinction between meaning 2 and meaning 3.

Are there any instances in an official rule book where it becomes clear in which sense the word threat is used in view of the game mechanics?

PS: I am aware that this problem can be solved by using pdf versions of the books and CTRL+f, but I do not have these files.