Cannot open display

Hi,

I'm trying to generate a 4top production event I'd like to view on the screen my Feynman diagrams, but this is what appears on my terminal when I run the "display diagrams" command (I've already installed an eps viewer program):

MG5_aMC>generate p p > t t t~ t~
INFO: Checking for minimal orders which gives processes.
INFO: Please specify coupling orders to bypass this step.
INFO: Trying coupling order WEIGHTED<=4: WEIGTHED IS QCD+2*QED
INFO: Trying process: g g > t t t~ t~ WEIGHTED<=4 @1
INFO: Process has 72 diagrams
INFO: Trying process: u u~ > t t t~ t~ WEIGHTED<=4 @1
INFO: Process has 14 diagrams
INFO: Trying process: u c~ > t t t~ t~ WEIGHTED<=4 @1
INFO: Trying process: c u~ > t t t~ t~ WEIGHTED<=4 @1
INFO: Trying process: c c~ > t t t~ t~ WEIGHTED<=4 @1
INFO: Process has 14 diagrams
INFO: Trying process: d d~ > t t t~ t~ WEIGHTED<=4 @1
INFO: Process has 14 diagrams
INFO: Trying process: d s~ > t t t~ t~ WEIGHTED<=4 @1
INFO: Trying process: s d~ > t t t~ t~ WEIGHTED<=4 @1
INFO: Trying process: s s~ > t t t~ t~ WEIGHTED<=4 @1
INFO: Process has 14 diagrams
INFO: Process u~ u > t t t~ t~ added to mirror process u u~ > t t t~ t~
INFO: Process c~ c > t t t~ t~ added to mirror process c c~ > t t t~ t~
INFO: Process d~ d > t t t~ t~ added to mirror process d d~ > t t t~ t~
INFO: Process s~ s > t t t~ t~ added to mirror process s s~ > t t t~ t~
5 processes with 128 diagrams generated in 1.107 s
Total: 5 processes with 128 diagrams
MG5_aMC>display diagrams
Drawing Process: g g > t t t~ t~ WEIGHTED<=4 @1
Wrote file /tmp/diagrams_1_gg_tttxtx.eps
open /tmp/diagrams_1_gg_tttxtx.eps
Drawing Process: u u~ > t t t~ t~ WEIGHTED<=4 @1
Wrote file /tmp/diagrams_1_uux_tttxtx.eps
open /tmp/diagrams_1_uux_tttxtx.eps
Drawing Process: c c~ > t t t~ t~ WEIGHTED<=4 @1
Wrote file /tmp/diagrams_1_ccx_tttxtx.eps
open /tmp/diagrams_1_ccx_tttxtx.eps
Drawing Process: d d~ > t t t~ t~ WEIGHTED<=4 @1
Wrote file /tmp/diagrams_1_ddx_tttxtx.eps
open /tmp/diagrams_1_ddx_tttxtx.eps
Drawing Process: s s~ > t t t~ t~ WEIGHTED<=4 @1
Wrote file /tmp/diagrams_1_ssx_tttxtx.eps
open /tmp/diagrams_1_ssx_tttxtx.eps
time to draw 0.5221724510192871
MG5_aMC>Unable to init server: Could not connect: Connection refused
Unable to init server: Could not connect: Connection refused
Unable to init server: Could not connect: Connection refused
Unable to init server: Could not connect: Connection refused
Unable to init server: Could not connect: Connection refused
Cannot parse arguments: Cannot open display:
Cannot parse arguments: Cannot open display:
Cannot parse arguments: Cannot open display:
Cannot parse arguments: Cannot open display:
Cannot parse arguments: Cannot open display:

How can I solve this problem? Thanks for your answer!