The equation of circular loops of cosmic string with time-dependent tension is studied in the Minkowski spacetime and Robertson-Walker universe. We find that, in the case where the tension depends on some power of the cosmic time, cosmic string loops with time-varying tension should not collapse to form a black hole if the power is lower than a critical value.
The circular loop equation of a cosmic string with time-varying tension in de Sitter spacetimes
本文研究了de Sitter时空中具有含时张力的宇宙弦圆环方程。我们发现初始半径为$r(t_{0})>0.707L$，L de Sitter半径的宇宙弦环不应该坍缩形成一个黑洞.在$r(t_{0})<0.707L$的情况下，如果宇宙时间的幂次小于一个临界值，则其张力依赖于宇宙时间幂次的宇宙弦环不能成为黑洞，该临界值与宇宙弦环的初始尺寸有关。
Braneworld scenarios appear in dynamical string tension theories, where string tension is positive between two surfaces separated by a short distance and at the two surfaces themselves the string tensions become infinite, therefore producing an effective confinement of the strings and therefore of all matter and gravity to the space between these to surfaces. The specific model studied is in the context of the modified measure formulation the string where tension appear as an additional dynamical degree of freedom and these tensions are not universal, but rather each string generates its own t…
The string tension does not have to be put in by hand, it can be dynamically generated, as in the case when we formulate string theory in the modified measure formalism, and other formulations as well. Then string tension appears, but as an additional dynamical degree of freedom . It can be seen however that this string tension is not universal, but rather each string generates its own string tension, which can have a different value for each string. We also define a new Tension scalar background field which change locally the value of the string tension along the world sheets of the strings. …
String tension fundamentally determines the properties of strings; yet its value is often assigned arbitrarily, creating a fine-tuning problem. We describe a mechanism for dynamically generating string tension in a flat or almost flat spacetime, using the modified measures formalism, which in turn naturally generates a new type of stringy brane-world scenario. Such a scenario allows strings to achieve near infinite tension confining the strings to two very close expanding surfaces, but the infinite tensions also threatens to distort the near-flat embedding spacetime through large back reaction…
In the modified measure formulation the string tension appear as an additional dynamical degree of freedom and these tensions are not universal, but rather each string generates its own tension, which can have a different value for each string. We consider new background field that can couple to these strings, the tension scalar is capable of changing locally along the world sheet the value of the tension of the extended object. When many types of strings probing the same region of space are considered this tension scalar is constrained by the requirement of quantum conformal invariance. For t…
We show that at large distances from an infinitely long global U(1) string, low energy Goldstone Bosons contribute a spatially dependent term to the energy density which is non-integrable. Specifically, this term diverges with the same form as the classical field theory contribution to the string tension, except with negative sign. This suggests that a careful analysis of the infrared degrees of freedom around the global string ought to yield an effective theory of the solitary string whose tension is finite. There are implications for axion cosmology.
Coulomb vs. physical string tension on the lattice
从连续介质的研究可知，库仑弦张力$σ_C$给出了物理（威尔逊）弦张力$σ_W$的上限[D. Zwanziger，Phys. Rev. Lett. 90，102001（2003）]。然而，这种关系如何转化为晶格？在本文中，我们给出的证据表明，有，而两个弦的张力在零温度相关，他们在有限的温度解耦。更准确地说，我们表明，在晶格上的库仑规范约束的情况下，总是绑定到空间弦张力，这是已知的生存的解除禁闭相变，并导致屏蔽效应的夸克-胶子等离子体。我们的分析是基于识别和消除中心涡，允许控制物理弦张力和研究其对库仑规范观测值的影响。我们还展示了库仑势的替代定义如何感知解除禁闭的转变，然而，一个真正的静态库仑规范序参量的相变仍然是难以捉摸的晶格上。
