32 research outputs found

### Semi-classical black holes with large N re-scaling and information loss problem

We consider semi-classical black holes and related re-scalings with N
massless fields. For a given semi-classical solution of an N = 1 universe, we
can find other solution of a large N universe by the re-scaling. After the
re-scaling, any curvature quantity takes a sufficiently small value without
changing its causal structure. Via the re-scaling, we argue that black hole
complementarity for semi-classical black holes cannot provide a fundamental
resolution of the information loss problem, and the violation of black hole
complementarity requires sufficiently reasonable amounts of N. Such N might be
realized from some string inspired models. Finally, we claim that any
fundamental resolution of the information loss problem should resolve the
problem of the singularity.Comment: 33 pages, 5 figure

### Small-scale Effects of Thermal Inflation on Halo Abundance at High-$z$, Galaxy Substructure Abundance and 21-cm Power Spectrum

We study the impact of thermal inflation on the formation of cosmological
structures and present astrophysical observables which can be used to constrain
and possibly probe the thermal inflation scenario. These are dark matter halo
abundance at high redshifts, satellite galaxy abundance in the Milky Way, and
fluctuation in the 21-cm radiation background before the epoch of reionization.
The thermal inflation scenario leaves a characteristic signature on the matter
power spectrum by boosting the amplitude at a specific wavenumber determined by
the number of e-foldings during thermal inflation ($N_{\rm bc}$), and strongly
suppressing the amplitude for modes at smaller scales. For a reasonable range
of parameter space, one of the consequences is the suppression of minihalo
formation at high redshifts and that of satellite galaxies in the Milky Way.
While this effect is substantial, it is degenerate with other cosmological or
astrophysical effects. The power spectrum of the 21-cm background probes this
impact more directly, and its observation may be the best way to constrain the
thermal inflation scenario due to the characteristic signature in the power
spectrum. The Square Kilometre Array (SKA) in phase 1 (SKA1) has sensitivity
large enough to achieve this goal for models with $N_{\rm bc}\gtrsim 26$ if a
10000-hr observation is performed. The final phase SKA, with anticipated
sensitivity about an order of magnitude higher, seems more promising and will
cover a wider parameter space.Comment: 28 pages, 8 figure

### The Possibility of Inflation in Asymptotically Safe Gravity

We examine the inflationary modes in the cubic curvature theories in the
context of asymptotically safe gravity. On the phase space of the Hubble
parameter, there exists a critical point which corresponds to the slow-roll
inflation in Einstein frame. Most of the e-foldings are attained around the
critical point for each inflationary trajectories. If the coupling constants
$g_i$ have the parametric relations generated as the power of the relative
energy scale of inflation $H_0$ to the ultraviolet cutoff $\Lambda$, a
successful inflation with more than 60 e-foldings occurs near the critical
point.Comment: 14 pages, 4 figure

### Critical Reviews of Causal Patch Measure over the Multiverse

In this talk, the causal patch measure based on black hole complementarity is
critically reviewed. By noticing the similarities between the causal structure
of an inflationary dS space and that of a black hole, we have considered the
complementarity principle between the inside and the outside of the causal
horizon as an attractive way to count the inflationary multiverse. Even though
the causal patch measure relieves the Boltzmann brain problem and stresses
physical reality based on observations, it could be challenged by the
construction of counterexamples, both on regular black holes and charged black
holes, to black hole complementarity.Comment: 6 pages, 2 figures; A proceeding for CosPA2008. Talk on the 29th of
October, 2008, Pohang, Kore

### How can we erase states inside a black hole?

We investigate an entangled system, which is analogous to a composite system
of a black hole and Hawking radiation. If Hawking radiation is well
approximated by an outgoing particle generated from pair creation around the
black hole, such a pair creation increases the total number of states. There
should be a unitary mechanism to reduce the number of states inside the horizon
for black hole evaporation. Because the infalling antiparticle has negative
energy, as long as the infalling antiparticle finds its partner such that the
two particles form a separable state, one can trace out such a zero energy
system by maintaining unitarity. In this paper, based on some toy model
calculations, we show that such a unitary tracing-out process is only possible
before the Page time while it is impossible after the Page time. Hence, after
the Page time, if we assume that the process is unitary and the Hawking pair
forms a separable state, the internal number of states will monotonically
increase, which is supported by the Almheiri-Marolf-Polchinski-Sully (AMPS)
argument. In addition, the Hawking particles cannot generate randomness of the
entire system; hence, the entanglement entropy cannot reach its maximum. Based
on these results, we modify the correct form of the Page curve for the remnant
picture. The most important conclusion is this: if we assume unitarity,
semi-classical quantum field theory, and general relativity, then the black
hole should violate the Bekenstein-Hawking entropy bound around the Page time
at the latest; hence, the infinite production arguments for remnants might be
applied for semi-classical black holes, which seems very problematic.Comment: 18 pages, 7 figure

### CMB Spectral Distortion Constraints on Thermal Inflation

Thermal inflation is a second epoch of exponential expansion at typical
energy scales $V^{1/4} \sim 10^{6 \sim 8} \mathrm{GeV}$. If the usual
primordial inflation is followed by thermal inflation, the primordial power
spectrum is only modestly redshifted on large scales, but strongly suppressed
on scales smaller than the horizon size at the beginning of thermal inflation,
$k > k_{\rm b} = a_{\rm b} H_{\rm b}$. We calculate the spectral distortion of
the cosmic microwave background generated by the dissipation of acoustic waves
in this context. For $k_{\rm b} \ll 10^3 \mathrm{Mpc}^{-1}$, thermal inflation
results in a large suppression of the $\mu$-distortion amplitude, predicting
that it falls well below the standard value of $\mu \simeq 2\times 10^{-8}$.
Thus, future spectral distortion experiments, similar to PIXIE, can place new
limits on the thermal inflation scenario, constraining $k_{\rm b} \gtrsim 10^3
\mathrm{Mpc}^{-1}$ if $\mu \simeq 2\times 10^{-8}$ were found.Comment: 18 pages, 7 figure

### CMB Spectral $\mu$-Distortion of Multiple Inflation Scenario

In multiple inflation scenario having two inflations with an intermediate
matter-dominated phase, the power spectrum is estimated to be enhanced on
scales smaller than the horizon size at the beginning of the second inflation,
$k > k_{\rm b}$. We require $k_{\rm b} > 10 {\rm Mpc}^{-1}$ to make sure that
the enhanced power spectrum is consistent with large scale observation of
cosmic microwave background (CMB). We consider the CMB spectral distortions
generated by the dissipation of acoustic waves to constrain the power spectrum.
The $\mu$-distortion value can be $10$ times larger than the expectation of the
standard $\Lambda$CDM model ($\mu_{\Lambda\mathrm{CDM}} \simeq 2 \times
10^{-8}$) for $k_{\rm b} \lesssim 10^3 {\rm Mpc}^{-1}$, while the
$y$-distortion is hardly affected by the enhancement of the power spectrum.Comment: 16 pages, 5 figure

### Modeling Cosmological Perturbations of Thermal Inflation

We consider a simple system consisting of matter, radiation and vacuum
components to model the impact of thermal inflation on the evolution of
primordial perturbations. The vacuum energy magnifies the modes entering the
horizon before its domination, making them potentially observable, and the
resulting transfer function reflects the phase changes and energy contents. To
determine the transfer function, we follow the curvature perturbation from well
outside the horizon during radiation domination to well outside the horizon
during vacuum domination and evaluate it on a constant radiation density
hypersurface, as is appropriate for the case of thermal inflation. The shape of
the transfer function is determined by the ratio of vacuum energy to radiation
at matter-radiation equality, which we denote by $\upsilon$, and has two
characteristic scales, $k_{\rm a}$ and $k_{\rm b}$, corresponding to the
horizon sizes at matter radiation equality and the beginning of the inflation,
respectively. If $\upsilon \ll 1$, the universe experiences radiation, matter
and vacuum domination eras and the transfer function is flat for $k \ll k_{\rm
b}$, oscillates with amplitude $1/5$ for $k_{\rm b} \ll k \ll k_{\rm a}$ and
oscillates with amplitude $1$ for $k \gg k_{\rm a}$. For $\upsilon \gg 1$, the
matter domination era disappears, and the transfer function reduces to being
flat for $k \ll k_{\rm b}$ and oscillating with amplitude $1$ for $k \gg k_{\rm
b}$.Comment: 17 pages, 5 figures, submitted to JCA