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<p><span id="ms-rterangepaste-start"></span><span id="docs-internal-guid-fcaed554-7fff-44ab-7ce3-829b9807ce12"></span></p>
<p dir="ltr" style="line-height:1.38; margin-top:0pt; margin-bottom:0pt"><span style="font-size:11pt; font-family:Arial; background-color:transparent; vertical-align:baseline; white-space:pre-wrap">Dear All,</span></p>
<br>
<p dir="ltr" style="line-height:1.38; margin-top:0pt; margin-bottom:0pt"><span style="font-size:11pt; font-family:Arial; background-color:transparent; vertical-align:baseline; white-space:pre-wrap">We will meet again for our next C&G seminar on 27th February
</span><span style="background-color: transparent; font-family: Arial; font-size: 11pt; white-space: pre-wrap;">at 13:15 in room number FC61, department of Astronomy.
</span><span style="background-color: transparent; font-family: Arial; font-size: 11pt; white-space: pre-wrap;">Axel Brandenburg from Nordita will give a seminar on the following
</span><span style="background-color: transparent; font-family: Arial; font-size: 11pt; white-space: pre-wrap;">topic:</span></p>
<br>
<p dir="ltr" style="line-height:1.38; margin-top:0pt; margin-bottom:0pt"><span style="font-size:11pt; font-family:Arial; background-color:transparent; vertical-align:baseline; white-space:pre-wrap">Title: Numerical simulations of gravitational waves from early
universe turbulence</span></p>
<br>
<p dir="ltr" style="line-height:1.38; margin-top:0pt; margin-bottom:0pt"><span style="font-size:11pt; font-family:Arial; background-color:transparent; vertical-align:baseline; white-space:pre-wrap">Abstract:
</span></p>
<p dir="ltr" style="line-height:1.38; margin-top:0pt; margin-bottom:0pt"><span style="font-size:11pt; font-family:Arial; background-color:transparent; vertical-align:baseline; white-space:pre-wrap">Using direct numerical simulations of early universe hydromagnetic
turbulence with energy densities of up to 10% of the radiation energy </span><span style="background-color: transparent; font-family: Arial; font-size: 11pt; white-space: pre-wrap;">density, we show that gravitational waves (GWs) with energy</span></p>
<p dir="ltr" style="line-height:1.38; margin-top:0pt; margin-bottom:0pt"><span style="font-size:11pt; font-family:Arial; background-color:transparent; vertical-align:baseline; white-space:pre-wrap">densities
</span><span style="background-color: transparent; font-family: Arial; font-size: 11pt; white-space: pre-wrap;">of about 10^{-10} times the critical energy density of the
</span><span style="background-color: transparent; font-size: 11pt; font-family: Arial; vertical-align: baseline; white-space: pre-wrap;">Friedmann
</span><span style="background-color: transparent; font-family: Arial; font-size: 11pt; white-space: pre-wrap;">universe today were produced. Their characteristic strain today
</span><span style="background-color: transparent; font-family: Arial; font-size: 11pt; white-space: pre-wrap;">is
</span><span style="background-color: transparent; font-family: Arial; font-size: 11pt; white-space: pre-wrap;">found to be about 10^{-20} and should be observable with the
</span><span style="background-color: transparent; font-family: Arial; font-size: 11pt; white-space: pre-wrap;">Laser
</span><span style="background-color: transparent; font-family: Arial; font-size: 11pt; white-space: pre-wrap;">Interferometer Space Antenna (LISA) in the mHz range. The GWs
</span><span style="background-color: transparent; font-family: Arial; font-size: 11pt; white-space: pre-wrap;">have positive (negative) circular polarization if the magnetic
</span><span style="background-color: transparent; font-family: Arial; font-size: 11pt; white-space: pre-wrap;">field has
</span><span style="background-color: transparent; font-family: Arial; font-size: 11pt; white-space: pre-wrap;">positive (negative) magnetic helicity. The GW energy reaches
</span><span style="background-color: transparent; font-family: Arial; font-size: 11pt; white-space: pre-wrap;">a
</span><span style="background-color: transparent; font-family: Arial; font-size: 11pt; white-space: pre-wrap;">constant value after the turbulent energy (kinetic or magnetic)
</span><span style="background-color: transparent; font-family: Arial; font-size: 11pt; white-space: pre-wrap;">has
</span><span style="background-color: transparent; font-family: Arial; font-size: 11pt; white-space: pre-wrap;">reached its maximum. Compressive modes are found to produce
</span><span style="background-color: transparent; font-family: Arial; font-size: 11pt; white-space: pre-wrap;">about 10 times stronger GWs than solenoidal ones. After a fraction
</span><span style="background-color: transparent; font-family: Arial; font-size: 11pt; white-space: pre-wrap;">of the Hubble time, a new shallow low frequency tail develops,
</span><span style="background-color: transparent; font-family: Arial; font-size: 11pt; white-space: pre-wrap;">which
</span><span style="background-color: transparent; font-family: Arial; font-size: 11pt; white-space: pre-wrap;">is shown not to be an artifact of a finite domain size.</span></p>
<br>
<p dir="ltr" style="line-height:1.38; margin-top:0pt; margin-bottom:0pt"><span style="font-size:11pt; font-family:Arial; background-color:transparent; vertical-align:baseline; white-space:pre-wrap">Date: February 27, Wednesday</span></p>
<p dir="ltr" style="line-height:1.38; margin-top:0pt; margin-bottom:0pt"><span style="font-size:11pt; font-family:Arial; background-color:transparent; vertical-align:baseline; white-space:pre-wrap">Time: 13:15</span></p>
<p dir="ltr" style="line-height:1.38; margin-top:0pt; margin-bottom:0pt"><span style="font-size:11pt; font-family:Arial; background-color:transparent; vertical-align:baseline; white-space:pre-wrap">Place: FC61</span></p>
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<p dir="ltr" style="line-height:1.38; margin-top:0pt; margin-bottom:0pt"><span style="font-size:11pt; font-family:Arial; background-color:transparent; vertical-align:baseline; white-space:pre-wrap">Cheers,</span></p>
<p dir="ltr" style="line-height:1.38; margin-top:0pt; margin-bottom:0pt"><span style="font-size:11pt; font-family:Arial; background-color:transparent; vertical-align:baseline; white-space:pre-wrap">Jens, Raghu, Justin & Steffen</span></p>
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