How to remove a singularity

• To: mathgroup at smc.vnet.net
• Subject: [mg130520] How to remove a singularity
• From: William Duhe <williamduhe at hotmail.com>
• Date: Thu, 18 Apr 2013 05:34:35 -0400 (EDT)
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• Delivered-to: l-mathgroup@wolfram.com
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```Bellow I have a differential equation which hits a singularity at low values of t. What I want to do is somehow utilize the WhenEvent command in order to replace the last factor of the equation (2/t a'[t]) with 0 at low values of t in order to avoid getting errors. Is there a way to do this?

Here is an example of the equation and how I attempted to use the Whenevent Command.

q = NDSolve[{a''[t] == 1/2 a[t]^2 + 1/6 a[t]^6 - 1/4 a[t]^4 - 2/t a'[t], a[0] == 1, a'[0] == 0, WhenEvent[t < .1, a'[t] -> 0]}, a, {t, 0, 1}];

any help would be appreciated!

```

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