What is the source of gravitational repulsion in certain cases?

  • Context: Graduate 
  • Thread starter Thread starter juan avellaneda
  • Start date Start date
  • Tags Tags
    Nuclei
Click For Summary

Discussion Overview

The discussion explores the nature of gravitational forces, particularly focusing on the concept of gravitational repulsion in certain contexts, as well as the balance of forces within atomic nuclei. It addresses theoretical aspects related to nuclear forces and gravitational interactions, including potential energy models.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions what prevents atomic nuclei from collapsing, referencing a "repulsive core" in the nuclear force.
  • Another participant explains the Yukawa potential, noting that at small distances, nucleons experience a strong repulsive force, while at larger distances, the force becomes attractive.
  • A different participant suggests that the nature of forces may depend on quark spin orientation, indicating a complexity in force interactions.
  • One participant asserts that gravity is typically always attractive, while another counters that there are scenarios where gravity can exhibit repulsive characteristics, particularly involving negative pressure and cosmological constants.
  • A specific example of gravitational repulsion is mentioned, involving vacuum domain walls in cosmology.

Areas of Agreement / Disagreement

Participants express differing views on the nature of gravitational forces, with some asserting gravity's inherent attractiveness while others propose conditions under which gravitational repulsion can occur. The discussion remains unresolved regarding the implications of these ideas.

Contextual Notes

The discussion touches on complex interactions between forces, including the dependence on various physical conditions such as pressure and quark properties, which may not be fully defined or agreed upon by participants.

juan avellaneda
Messages
37
Reaction score
0
i was wondering this

if the nuclear force overcomes the electromagnetic force in the nucleus, then what prevents the nuclei for colapse itself

i read in somewhere this
" the nuclear force has a repulsive core which prevents the nuclei from collapsing in on themselves"

what is this "repulsive core"?
 
Physics news on Phys.org
The potential energy between two nucleons obeys the Yukawa potential. At small separation distances the potential energy is positive, and there is a strong repulsive force between the two nucleons. At larger distances, the potential energy is negative, and there is an attractive force. You can search for Yukawa potential and find out everything you want to know.
 
nuclei

many thanks for your reply, it seems that all forces are not always attractive or repulsive, but dependes of quarks spin orientation in the particles
thats what i understood in some lecture i attend
 
Except gravity. As far as we can tell, gravity is always attractive.
 
Originally posted by FZ+
Except gravity. As far as we can tell, gravity is always attractive.

In some cases gravity is replusive. This happens because pressure is also a source of gravity and because a non-zero cosmological constant gives gravitational repulsion.

When there is a negative pressure present in that source which is so large as to overcome the attractive source due to other sources like mass terms in Einstein's equations, then there can be a resulsive effect.

A vacuum domain wall is a well-known example from cosmology.
 

Similar threads

  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 5 ·
Replies
5
Views
3K
  • · Replies 13 ·
Replies
13
Views
3K
  • · Replies 13 ·
Replies
13
Views
3K
  • · Replies 12 ·
Replies
12
Views
5K
  • · Replies 22 ·
Replies
22
Views
7K
  • · Replies 3 ·
Replies
3
Views
9K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 6 ·
Replies
6
Views
3K
  • · Replies 4 ·
Replies
4
Views
5K