竹子 · 2018年05月23日
如果你想到的是对BSM模型的解释，即call相当于是Long stock同时short bond(发行债券融资），那其实是一样的。
因为这一题说了因为call overpirced，所以short call。正常的思路是：short call有风险且风险很大，但套利是无风险的，所以需要long stock来对冲股票价格上涨时short call的亏损。但long stock钱不够，套利是空手套白狼，因此需要borrow。
但其实你再想一下，现在你short call，套利其实就是买一个再卖一个。根据BSM的解释，long stock+borrow这个头寸其实就是合成了一个call option，但这个call option是我们认为的合理认定，而市场中的call option是overpriced，所以整个过程也可以理解为低买高卖。
两种想法是相通的，只不过用BSM来想有点复杂，不如用套利的两个特点（无风险，空手套白狼）简单。
NO.PZ201702190300000304 问题如下 For the Alpha Company option, the positions to take aantage of the arbitrage opportunity are to write the call an A.short shares of Alpha stoanlen B.buy shares of Alpha stoanborrow. C.short shares of Alpha stoanborrow. B is correct.You shoulsell (write) the overpricecall option anthen go long (buy) the replicating portfolio for a call option. The replicating portfolio for a call option is to buy h shares of the stoanborrow the present value of (hS- - c-).c = hS + PV(-hS- + c-).h = (- c-)/(S+ - S-) = (6 - 0)/(56 - 46) = 0.60.For the example in this case, the value of the call option is 3.714. If the option is overpriceat, say, 4.50, you short the option anhave a cash flow Time 0 of +4.50. You buy the replicating portfolio of 0.60 shares 50 per share (giving you a cash flow of -30) anborrow (1/1.05) x [(0.60 x 46) - 0] = (1/1.05) x 27.6 = 26.287. Your cash flow for buying the replicating portfolio is -30 + 26.287 = -3.713. Your net cash flow Time 0 is + 4.50 - 3.713 = 0.787. Your net cash flow Time 1 for either the up move or wn move is zero. You have ma arbitrage profit of 0.787.In tabulform, the cash flows are follows:中文解析根据题干信息可知，当前的市场上关于Alpha公司的看涨期权是被高估的，因此套利操作下我们可以卖出被高估的买进被低估的，因此正如本题问题中表述的已经卖出了看涨期权，然后需要的操作是买入一个合成的看涨期权。看涨期权的合成相当于借钱买股票，因此本题选 谢谢
NO.PZ201702190300000304问题如下 For the Alpha Company option, the positions to take aantage of the arbitrage opportunity are to write the call an A.short shares of Alpha stoanlenB.buy shares of Alpha stoanborrow.C.short shares of Alpha stoanborrow. B is correct.You shoulsell (write) the overpricecall option anthen go long (buy) the replicating portfolio for a call option. The replicating portfolio for a call option is to buy h shares of the stoanborrow the present value of (hS- - c-).c = hS + PV(-hS- + c-).h = (- c-)/(S+ - S-) = (6 - 0)/(56 - 46) = 0.60.For the example in this case, the value of the call option is 3.714. If the option is overpriceat, say, 4.50, you short the option anhave a cash flow Time 0 of +4.50. You buy the replicating portfolio of 0.60 shares 50 per share (giving you a cash flow of -30) anborrow (1/1.05) x [(0.60 x 46) - 0] = (1/1.05) x 27.6 = 26.287. Your cash flow for buying the replicating portfolio is -30 + 26.287 = -3.713. Your net cash flow Time 0 is + 4.50 - 3.713 = 0.787. Your net cash flow Time 1 for either the up move or wn move is zero. You have ma arbitrage profit of 0.787.In tabulform, the cash flows are follows:中文解析根据题干信息可知，当前的市场上关于Alpha公司的看涨期权是被高估的，因此套利操作下我们可以卖出被高估的买进被低估的，因此正如本题问题中表述的已经卖出了看涨期权，然后需要的操作是买入一个合成的看涨期权。看涨期权的合成相当于借钱买股票，因此本题选题干说了是short call，直接用ck=ps不就好了吗，感觉解析说的太复杂了吧
NO.PZ201702190300000304 问题如下 For the Alpha Company option, the positions to take aantage of the arbitrage opportunity are to write the call an A.short shares of Alpha stoanlen B.buy shares of Alpha stoanborrow. C.short shares of Alpha stoanborrow. B is correct.You shoulsell (write) the overpricecall option anthen go long (buy) the replicating portfolio for a call option. The replicating portfolio for a call option is to buy h shares of the stoanborrow the present value of (hS- - c-).c = hS + PV(-hS- + c-).h = (- c-)/(S+ - S-) = (6 - 0)/(56 - 46) = 0.60.For the example in this case, the value of the call option is 3.714. If the option is overpriceat, say, 4.50, you short the option anhave a cash flow Time 0 of +4.50. You buy the replicating portfolio of 0.60 shares 50 per share (giving you a cash flow of -30) anborrow (1/1.05) x [(0.60 x 46) - 0] = (1/1.05) x 27.6 = 26.287. Your cash flow for buying the replicating portfolio is -30 + 26.287 = -3.713. Your net cash flow Time 0 is + 4.50 - 3.713 = 0.787. Your net cash flow Time 1 for either the up move or wn move is zero. You have ma arbitrage profit of 0.787.In tabulform, the cash flows are follows:中文解析根据题干信息可知，当前的市场上关于Alpha公司的看涨期权是被高估的，因此套利操作下我们可以卖出被高估的买进被低估的，因此正如本题问题中表述的已经卖出了看涨期权，然后需要的操作是买入一个合成的看涨期权。看涨期权的合成相当于借钱买股票，因此本题选 老师，前面我都看懂了，在t=0时刻卖出被高估的看涨期权，买入合成的看涨期权，arbitrage profit=price-value=0.786，但是请问Your net cash flow Time 1 for either the up move or wn move is zero. 这句话是什么意思？
NO.PZ201702190300000304 1.这个题目没说是BSMmol ，看提问有的成了BSMmol。 1.1课件142页写的 call option =long stock+short bon以这道题？那这里的short 对应答案B里面的borrow bon为什么？ 1.2不理解如果有put option这题的答案还有什么？ 2.课件101页写的call=unlying anfinancing这里指代的是long call ?还是long或者short call？ 3.课件102 页是long put，short sell the unrlying anlen?这里是这道题？可这题目说的意思short call，不是long put 4.因为overpricecall推出的short call？ 5.那按照里的For the example in this case, the value of the call option is 3.714. 这个值是无套利定价下的合理价值？ 6.能否一下答案里的例子答案，我就没明白时代1和0之间的变化。谢谢
NO.PZ201702190300000304 老师，你好，c+k=p+s，现在是-c（short call)，为什么不是-c=-s-p+k？就是put stock？
