# The anamorphic universe

## Abstract

We introduce ''anamorphic'' cosmology, an approach for explaining the smoothness and flatness of the universe on large scales and the generation of a nearly scale-invariant spectrum of adiabatic density perturbations. The defining feature is a smoothing phase that acts like a contracting universe based on some Weyl frame-invariant criteria and an expanding universe based on other frame-invariant criteria. An advantage of the contracting aspects is that it is possible to avoid the multiverse and measure problems that arise in inflationary models. Unlike ekpyrotic models, anamorphic models can be constructed using only a single field and can generate a nearly scale-invariant spectrum of tensor perturbations. Anamorphic models also differ from pre-big bang and matter bounce models that do not explain the smoothness. We present some examples of cosmological models that incorporate an anamorphic smoothing phase.

- Authors:

- Princeton Center for Theoretical Science, Princeton University, Princeton, NJ, 08544 (United States)

- Publication Date:

- OSTI Identifier:
- 22525302

- Resource Type:
- Journal Article

- Journal Name:
- Journal of Cosmology and Astroparticle Physics

- Additional Journal Information:
- Journal Volume: 2015; Journal Issue: 10; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 1475-7516

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; COSMOLOGICAL MODELS; COSMOLOGY; DENSITY; DISTURBANCES; ROUGHNESS; SCALE INVARIANCE; SMOOTH MANIFOLDS; TENSORS; UNIVERSE

### Citation Formats

```
Ijjas, Anna, and Steinhardt, Paul J., E-mail: aijjas@princeton.edu, E-mail: steinh@princeton.edu.
```*The anamorphic universe*. United States: N. p., 2015.
Web. doi:10.1088/1475-7516/2015/10/001.

```
Ijjas, Anna, & Steinhardt, Paul J., E-mail: aijjas@princeton.edu, E-mail: steinh@princeton.edu.
```*The anamorphic universe*. United States. doi:10.1088/1475-7516/2015/10/001.

```
Ijjas, Anna, and Steinhardt, Paul J., E-mail: aijjas@princeton.edu, E-mail: steinh@princeton.edu. Thu .
"The anamorphic universe". United States. doi:10.1088/1475-7516/2015/10/001.
```

```
@article{osti_22525302,
```

title = {The anamorphic universe},

author = {Ijjas, Anna and Steinhardt, Paul J., E-mail: aijjas@princeton.edu, E-mail: steinh@princeton.edu},

abstractNote = {We introduce ''anamorphic'' cosmology, an approach for explaining the smoothness and flatness of the universe on large scales and the generation of a nearly scale-invariant spectrum of adiabatic density perturbations. The defining feature is a smoothing phase that acts like a contracting universe based on some Weyl frame-invariant criteria and an expanding universe based on other frame-invariant criteria. An advantage of the contracting aspects is that it is possible to avoid the multiverse and measure problems that arise in inflationary models. Unlike ekpyrotic models, anamorphic models can be constructed using only a single field and can generate a nearly scale-invariant spectrum of tensor perturbations. Anamorphic models also differ from pre-big bang and matter bounce models that do not explain the smoothness. We present some examples of cosmological models that incorporate an anamorphic smoothing phase.},

doi = {10.1088/1475-7516/2015/10/001},

journal = {Journal of Cosmology and Astroparticle Physics},

issn = {1475-7516},

number = 10,

volume = 2015,

place = {United States},

year = {2015},

month = {10}

}