星际帝国 补给设想----食物资源

江左

要等24小时的吧，粉多论坛:loveliness:

江左

CP violation and the matter-antimatter imbalance
Main article: Baryogenesis
Unsolved problems in physics: Why does the universe have so much more matter than antimatter?One of the unsolved theoretical questions in physics is why the universe is made chiefly of matter, rather than consisting of equal parts of matter and antimatter. It can be demonstrated that to create an imbalance in matter and antimatter from an initial condition of balance, the Sakharov conditions must be satisfied, one of which is the existence of CP violation during the extreme conditions of the first seconds after the Big Bang. Explanations which do not involve CP violation are less plausible, since they rely on the assumption that the matter-antimatter imbalance was present at the beginning, or on other admittedly exotic assumptions.

The Big Bang should have produced equal amounts of matter and anti-matter if CP-symmetry was preserved; as such, there should have been total cancellation of both. In other words, protons should have cancelled with anti-protons, electrons with positrons, neutrons with anti-neutrons, and so on for all elementary particles. This would have resulted in a sea of photons in the universe with no matter. Since this is quite evidently not the case, after the Big Bang, physical laws must have acted differently for matter and antimatter, i.e. violating CP symmetry.

The Standard Model contains only two ways to break CP symmetry. The first of these, discussed above, is in the QCD lagrangian, and has not been found experimentally; but one would expect this to lead to either no CP violation or a CP violation that is many, many orders of magnitude too large. The second of these, involving the weak force, has been experimentally verified, but can account for only a small portion of CP-violation. It is predicted to be sufficient for a net mass of normal matter equivalent to only a single galaxy in the known universe.

Since the Standard Model does not accurately predict this discrepancy, it would seem that the current Standard Model has gaps (other than the obvious one of gravity and related matters) or physics is otherwise in error. Moreover, experiments to probe these CP-related gaps may not require the practically impossible-to-obtain energies that may be necessary to probe the gravity-related gaps (see Planck mass).
:lol :lol

江左

一种在科学界受到普遍认同的理论认为，宇宙大爆炸早期曾产生了数量相当的物质和反物质，随后发生的物质和反物质的湮灭消耗掉了绝大部分的正、反物质，遗留下的少部分正物质构成了现如今的物质世界。理論上宇宙大爆炸時所產生的粒子與反粒子應該數量相同，但是为什么現今所遺留下來的絕大多數都是正粒子，這即所谓的“正反物质对称性破壞”(對稱破缺)，雖然在幾個粒子对撞试验中，都發現了正粒子與反粒子的衰變略有不同，及所謂的電荷宇稱不守恆(CP破壞)，但在數量上仍不足以解釋為何現今反物質消失的問題，這在粒子物理学上仍是一大未解决的问题。

江左

看来，对于正反物质失衡，有两大类假设：

1 在开始的时候，正物质就比较多。支持这种假设的人比较少
2 开始的时候，正反物质一样多。但在湮灭过程中，由于宇称不守恒原则，正物质更少湮灭掉。但是宇称不守恒只在弱相互作用中得到部分证实，还不足以解释现在的物质世界是如何构成的。

不过，虽然有种种假设，但有一点是确认的，我们的周围并不存在一个反物质的世界:loveliness:

三袋米

没有结论的结论;P

江左

谈不上结论，只不过ArthurLing对于正反物质的解释有错误而已:lol

ArthurLing

汗，你理解问题的方式是错误，你找到来理论和我的解释并不冲突：

第一，理论上，正物质和反物质的数量应该相同。

第二，现在无法解释我们观测不到这么多数量的反物质。物理界对一些我们无法解释的现象，通常采用人择原理。

ArthurLing

你也说了，这些都是假设，但理论上，正反物质应该是数量相同的。这也是现在需要解决的问题而已。

ArthurLing

另外，不错，粒子衰变是不服从CP对称，但衰变并不是消失！

三袋米

ArthurLing 大大  请教一个问题

关于封闭系统

封闭系统有三个特性 1 与外界隔绝 2 不能产生物质交换 3 可以传递能量

这里俺就有个疑问了 HOHO

不是有种说法 能量既物质 吗？  那第二条和第三条不是矛盾了？？