281 research outputs found
Axial U(1) current in Grabowska and Kaplan's formulation
Recently, Grabowska and Kaplan suggested a non-perturbative formulation of a
chiral gauge theory, which consists of the conventional domain-wall fermion and
a gauge field that evolves by the gradient flow from one domain wall to the
other. In this paper, we discuss the U(1) axial-vector current in 4 dimensions
using this formulation. We introduce two sets of domain-wall fermions belonging
to complex conjugate representations so that the effective theory is a
4-dimensional vector-like gauge theory. Then, as a natural definition of the
axial-vector current, we consider a current that generates the simultaneous
phase transformations for the massless modes in 4 dimensions. However, this
current is exactly conserved and does not reproduce the correct anomaly. In
order to investigate this point precisely, we consider the mechanism of the
conservation. We find that this current includes not only the axial current on
the domain wall but also a contribution from the bulk, which is non-local in
the sense of 4-dimensional fields. Therefore, the local current is obtained by
subtracting the bulk contribution from it.Comment: 25 pages, 1 figur
Solving the Naturalness Problem by Baby Universes in the Lorentzian Multiverse
We propose a solution of the naturalness problem in the context of the
multiverse wavefunction without the anthropic argument. If we include
microscopic wormhole configurations in the path integral, the wave function
becomes a superposition of universes with various values of the coupling
constants such as the cosmological constant, the parameters in the Higgs
potential, and so on. We analyze the quantum state of the multiverse, and
evaluate the density matrix of one universe. We show that the coupling
constants induced by the wormholes are fixed in such a way that the density
matrix is maximized. In particular, the cosmological constant, which is in
general time-dependent, is chosen such that it takes an extremely small value
in the far future. We also discuss the gauge hierarchy problem and the strong
CP problem in this context. Our study predicts that the Higgs mass is 140\pm20
GeV and {\theta}=0.Comment: 35 pages, 11 figures. v2: added Section 5.3 with comments on the Wick
rotation of the Lorentzian gravity. v3 some comments adde
Gravitational string-membrane hedgehog and internal structure of black holes
We investigate charged Nambu-Goto strings/membrane systems in the
Einstein-Maxwell theory in 3+1 dimensions. We first construct a charged string
hedgehog solution that has a single horizon and conical singularity. Then we
examine a charged membrane system, and give a simple derivation of its self
energy. We find that the membrane may form an extremal Reissner-Nordstrom black
hole, but its interior is a flat spacetime. Finally by combining the charged
strings and the membrane we construct black hole solutions that have no
singularities inside the horizons. We study them in detail by varying the
magnitude of the two parameters, namely, the charge times the membrane tension
and the string tension. We also argue that the strings have, due to the large
redshift inside the system, a fair amount of degrees of freedom that may
explain the entropy of the corresponding black holes.Comment: 22 pages, 13 figures, minor revisions, version published in PT
Weak scale from Planck scale -- Mass Scale Generation in Classically Conformal Two Scalar System --
In the standard model, the weak scale is the only parameter with mass
dimensions. This means that the standard model itself can not explain the
origin of the weak scale. On the other hand, from the results of recent
accelerator experiments, except for some small corrections, the standard model
has increased the possibility of being an effective theory up to the Planck
scale. From these facts, it is naturally inferred that the weak scale is
determined by some dynamics from the Planck scale. In order to answer this
question, we rely on the multiple point criticality principle as a clue and
consider the classically conformal invariant
two scalar model as a minimal model in which the weak scale is generated
dynamically from the Planck scale. This model contains only two real scalar
fields and does not contain any fermions and gauge fields. In this model, due
to Coleman-Weinberg-like mechanism, one scalar field spontaneously breaks the
symmetry with a vacuum expectation value connected with the
cutoff momentum. We investigate this using the 1-loop effective potential,
renormalization group and large N limit. We also investigate whether it is
possible to reproduce the mass term and vacuum expectation value of the Higgs
field by coupling this model with the standard model in the Higgs portal
framework. In this case, the one scalar field that does not break
can be a candidate for dark matter, and have a mass of about
several TeV in appropriate parameters. On the other hand, the other scalar
field breaks and has a mass of several tens of GeV. These
results can be verified in near future experiments.Comment: 41 pages, 9 figures, minor mistakes in Section VI.B and typos
correcte
Black Hole as a Quantum Field Configuration
We describe 4D evaporating black holes as quantum field configurations by
solving the semi-classical Einstein equation and quantum matter fields in a self-consistent
manner. As the matter fields we consider massless free scalar fields (
is large). We find a spherically symmetric self-consistent solution of the
metric and state . Here, is locally
geometry, and provides , where is the ground state of the
matter fields in the metric and consists of the
excitation of s-waves that describe the collapsing matter and Hawking radiation
with the ingoing negative energy flow. This object is supported by a large
tangential pressure due to the vacuum
fluctuation of the bound modes with large angular momenta. This describes the
interior of the black hole when the back reaction of the evaporation is
considered. The black hole is a compact object with a surface (instead of
horizon) that looks like a conventional black hole from the outside and
eventually evaporates without a singularity. If we count the number of
self-consistent configurations , we reproduce the area law of
the entropy. This tells that the information is carried by the s-waves inside
the black hole. also describes the process that the negative
ingoing energy flow created with Hawking radiation is superposed on the
collapsing matter to decrease the total energy while the total energy density
remains positive. As a special case, we consider conformal matter fields and
show that the interior metric is determined by the matter content of the
theory, which leads to a new constraint to the matter content.Comment: ver4: We added a new paragraph to Sec.2.1. and made Appendix
Interior of Black Holes and Information Recovery
We analyze time evolution of a spherically symmetric collapsing matter from a
point of view that black holes evaporate by nature. We first consider a
spherical thin shell that falls in the metric of an evaporating Schwarzschild
black hole of which the radius decreases in time. The important point is
that the shell can never reach but it approaches . This situation holds at any radius because the motion of a shell
in a spherically symmetric system is not affected by the outside. In this way,
we find that the collapsing matter evaporates without forming a horizon.
Nevertheless, a Hawking-like radiation is created in the metric, and the object
looks the same as a conventional black hole from the outside. We then discuss
how the information of the matter is recovered. We also consider a black hole
that is adiabatically grown in the heat bath and obtain the interior metric. We
show that it is the self-consistent solution of and that the four-dimensional Weyl anomaly induces the
radiation and a strong angular pressure. Finally, we analyze the internal
structures of the charged and the slowly rotating black holes.Comment: Appear in Physical Review D. Typos fixed. References, clarifications
and new appendixes adde
Phenomenological Description of the Interior of the Schwarzschild Black Hole
We discuss a sufficiently large 4-dimensional Schwarzschild black hole which
is in equilibrium with a heat bath. In other words, we consider a black hole
which has grown up from a small one in the heat bath adiabatically. We express
the metric of the interior of the black hole in terms of two functions: One is
the intensity of the Hawking radiation, and the other is the ratio between the
radiation energy and the pressure in the radial direction. Especially in the
case of conformal matters we check that it is a self-consistent solution of the
semi-classical Einstein equation, . It is shown that the strength of the Hawking radiation is
proportional to the c-coefficient, that is, the coefficient of the square of
the Weyl tensor in the 4-dimensional Weyl anomaly.Comment: 10 pages. Detail discussions and references added. Accepted Int. J.
Mod. Phys.
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