37 research outputs found
Conservation Laws from Asymptotic Symmetry and Subleading Charges in QED
We present several results on memory effects, asymptotic symmetry and soft
theorems in massive QED. We first clarify in what sense the memory effects are
interpreted as the charge conservation of the large gauge transformations, and
derive the leading and subleading memory effects in classical electromagnetism.
We also show that the sub-subleading charges are not conserved without
including contributions from the spacelike infinity. Next, we study QED in the
BRST formalism and show that parts of large gauge transformations are physical
symmetries by justifying that they are not gauge redundancies. Finally, we
obtain the expression of charges associated with the subleading soft photon
theorem in massive scalar QED.Comment: 23+13 pages, 1 figure; v2: title changed, appendix B modified,
references added and typos correcte
Soft pion theorem, asymptotic symmetry and new memory effect
It is known that soft photon and graviton theorems can be regarded as the
Ward-Takahashi identities of asymptotic symmetries. In this paper, we consider
soft theorem for pions, i.e., Nambu-Goldstone bosons associated with a
spontaneously broken axial symmetry. The soft pion theorem is written as the
Ward-Takahashi identities of the -matrix under asymptotic transformations.
We investigate the asymptotic dynamics, and find that the conservation of
charges generating the asymptotic transformations can be interpreted as a pion
memory effect.Comment: 25 pages, 2 figures, v2: references and discussions adde
Propagators in de Sitter space
In a spacetime with no global timelike Killing vector, we do not have a
natural choice for the vacuum state of matter fields, leading to an ambiguity
in defining the Feynman propagators. In this paper, taking the vacuum state to
be the instantaneous ground state of the Hamiltonian at each moment, we develop
a method for calculating wave functions associated with the vacuum and the
corresponding in-in and in-out propagators. We apply this method to free scalar
field theory in de Sitter space and obtain de Sitter invariant propagators in
various coordinate patches. We show that the in-out propagator in the Poincare
patch has a finite massless limit in a de Sitter invariant form. We argue and
numerically check that our in-out propagators agree with those obtained by a
path integral with the standard i\epsilon prescription, and identify the
condition on a foliation of spacetime under which such coincidence can happen
for the foliation. We also show that the in-out propagators satisfy Polyakov's
composition law. Several applications of our framework are also discussed.Comment: 38 pages, 14 figures, v2: references added, discussion on the in-in
propagators improved, v3: typos corrected, v4: references added, discussions
improved, to appear in PR
Ramond-Ramond couplings of D-branes
Applying supersymmetric localization for superstring worldsheet theory with
N=(1,1) supersymmetries on a cylinder and with arbitrary boundary interactions,
we find the most general formula for the Ramond-Ramond (RR) coupling of
D-branes. We allow all massive excitations of open superstrings, and find that
only a finite number of them can contribute to the formula. The formula is
written by Quillen's superconnection which includes higher form gauge fields,
and the resultant general Chern-Simons terms are consistent with RR charge
quantization. Applying the formula to boundary string field theory of a BPS
D9-brane or a D9-antiD9 brane system, we find that any D9-brane creation via
massive mode condensation is impossible.Comment: 24 pages, 1 figur
Matter fields in triangle-hinge models
The worldvolume theory of membrane is mathematically equivalent to
three-dimensional quantum gravity coupled to matter fields corresponding to the
target space coordinates of embedded membrane. In a recent paper
[arXiv:1503.08812] a new class of models are introduced that generate
three-dimensional random volumes, where the Boltzmann weight of each
configuration is given by the product of values assigned to the triangles and
the hinges. These triangle-hinge models describe three-dimensional pure gravity
and are characterized by semisimple associative algebras. In this paper, we
introduce matter degrees of freedom to the models by coloring simplices in a
way that they have local interactions. This is achieved simply by extending the
associative algebras of the original triangle-hinge models, and the profile of
matter field is specified by the set of colors and the form of interactions.
The dynamics of a membrane in -dimensional spacetime can then be described
by taking the set of colors to be . By taking another set of
colors, we can also realize three-dimensional quantum gravity coupled to the
Ising model, the -state Potts models or the RSOS models. One can actually
assign colors to simplices of any dimensions (tetrahedra, triangles, edges and
vertices), and three-dimensional colored tensor models can be realized as
triangle-hinge models by coloring tetrahedra, triangles and edges at a time.Comment: 21 pages, 14 figures. v2: discussions in section 4 improved. v3:
title changed, introduction enlarge
Master equation for the Unruh-DeWitt detector and the universal relaxation time in de Sitter space
We derive the master equation that completely determines the time evolution
of the density matrix of the Unruh-DeWitt detector in an arbitrary background
geometry. We apply the equation to reveal a nonequilibrium thermodynamic
character of de Sitter space. This generalizes an earlier study on the
thermodynamic property of the Bunch-Davies vacuum that an Unruh-DeWitt detector
staying in the Poincare patch and interacting with a scalar field in the
Bunch-Davies vacuum behaves as if it is in a thermal bath of finite
temperature. In this paper, instead of the Bunch-Davies vacuum, we consider a
class of initial states of scalar field, for which the detector behaves as if
it is in a medium that is not in thermodynamic equilibrium and that undergoes a
relaxation to the equilibrium corresponding to the Bunch-Davies vacuum. We give
a prescription for calculating the relaxation times of the nonequilibrium
processes. We particularly show that, when the initial state of the scalar
field is the instantaneous ground state at a finite past, the relaxation time
is always given by a universal value of half the curvature radius of de Sitter
space. We expect that the relaxation time gives a nonequilibrium thermodynamic
quantity intrinsic to de Sitter space.Comment: 41 pages, 10 figures; v2: typos corrected; v3: typos corrected; v4:
clarifications and references added; v5: final version appearing in PR
Holographic Holes in Higher Dimensions
We extend the holographic construction from AdS3 to higher dimensions. In
particular, we show that the Bekenstein-Hawking entropy of codimension-two
surfaces in the bulk with planar symmetry can be evaluated in terms of the
'differential entropy' in the boundary theory. The differential entropy is a
certain quantity constructed from the entanglement entropies associated with a
family of regions covering a Cauchy surface in the boundary geometry. We
demonstrate that a similar construction based on causal holographic information
fails in higher dimensions, as it typically yields divergent results. We also
show that our construction extends to holographic backgrounds other than AdS
spacetime and can accommodate Lovelock theories of higher curvature gravity.Comment: 46 pages, 17 figures, 1 appendi