<｜begin▁of▁sentence｜>### Instruction:
Given the Astrophysics collaborations Graph which you can read from a gml file named 'astro-ph.gml', can you apply the CoAch (core-attachment) algorithm to perform community detection using default parameters and output a JSON representation of the detected communities?
### Response:
import networkx as nx
from cdlib import algorithms

# Load the Astrophysics collaborations graph
g = nx.read_gml('astro-ph.gml')

# Apply the CoAch algorithm to detect communities using default parameters
communities = algorithms.coach(g)

# Generate a JSON representation of the detected communities
communities_json = communities.to_json()

print(communities_json)
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